Difference between revisions of "Category:702 Load-Bearing Piles"

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==702.1 Construction Inspection for [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702]==
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This article contains information about piling types and pile driving criteria used by Construction and Materials Division for on-site pile and pile driving inspection purposes (in the field). This information was part of the former Field Inspection Guidance of the Construction and Materials Manual (see [[:Category:106 Control of Material|EPG 106 Control of Materials]]) and is continually updated.
The principal function of piles is to transmit loads which cannot be adequately supported at normal footing levels, to a depth where adequate support is available. When a pile passes through poor material and its tip penetrates a small distance into a sound stratum of good bearing capacity, it is called a bearing pile. The material which is penetrated may vary all the way from water to materials that would ordinarily serve to support surface footings, but cannot be used because of severe settlement restrictions. When a pile extends part way through a deep strata of limited supporting ability and develops capacity by friction on the sides of the pile, with some end bearing characteristics, it is are called a friction pile. Types normally used as friction piles are cast-in-place concrete piles. Piles are used and classified as friction pile because principal support for the pile is from surface friction, not end
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bearing. All pile types may be used as "batter piles", (piles driven in a sloping position) to aid in resisting horizontal loads.
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|'''[[media:702 Pile Driving Set Calculator R201305.xlsx|Pile Driving Set Calculator]]'''
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==702.1 Pile Types and Testing==
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The principal function of piles is to transmit loads which cannot be adequately supported at normal footing levels, to a depth where adequate support is available.  
  
Piles for footings where footing surface is below finished ground are referred to as foundation
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When a pile passes through poor material and its tip penetrates a small distance into a sound stratum of good bearing capacity, it is called a bearing pile. The material which is penetrated may vary all the way from water to materials that would ordinarily serve to support surface footings, but cannot be used because of severe settlement restrictions.  
piles. Piles which support shallow caps, usually on intermediate bents, are called trestle
 
piles. Pile types are specified on the plans.
 
  
When a type of pile is specified, a pile standard is indexed on the bridge plans. This standard
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When a pile extends part way through deep strata of limited supporting resistance and capacity is developed primarily from surface friction along the sides of the pile with some end bearing, the pile is generally referred to as a friction pile. A type of pile normally used as a friction pile is a cast-in-place concrete pile(CIP pile).
will furnish specific details for the pile to be furnished.
 
  
There are two types of piles generally used by MoDOT. They are structural steel and cast in place concrete pile.
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A battered pile is a pile driven on an inclination (a sloping position) to aid in resisting horizontal loads.  
  
===702.1.1 Cast-in-place Concrete Pile (Sec 702.2.1)===
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Piles utilized as part of concrete footings where the piles are below the finished ground are referred to as foundation piles. The pile-footing system is generally referred to as a pile cap footing. Piles which support bent caps are called trestle piles and the pile-bent system is generally referred to as a pile cap bent.  
They consist of pre-driven shells of steel later filled with concrete. The most commonly used type of spirally welded steel, sometimes called pipe piles. This type pile normally has no internal reinforcement. Steel shells are usually driven without a mandrel if shell thickness permits. Where steel shells are driven, boulders or other obstructions quite often deflect the tubes from their intended course. This problem is magnified if piles are driven on a batter. This could result in bent or crushed shells. Metal shells shall hold the original form without distortion after being driven and shall be free from water, soil and other deleterious matter when concrete is cast in the shells. Any shell that has been bent or damaged should be carefully reviewed. Any decision to permit its use should be only with approval of the Bridge Division through the Division of Construction and Materials. Concrete should be directed down the center of the shell. Concrete hitting the sides can cause segregation. If concrete can be successfully directed down the center of the shell no tremie is required regardless of the height of fall.
 
  
===702.1.2 Structural Steel Pile (Sec 702.2.2)===
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Pile types are specified on the bridge plans.  
Structural steel piles are rolled H-Sections which are used in certain types of pile installations. This type of pile is probably the most widely used in the State of Missouri. These piles extend into the ground and transmit loads from footing to bearing stratum as columns. They displace a small volume of soil and can be driven with relatively close spacing. Pile tip reinforcement is sometimes specified when driving steel pile through boulders or thin layers of rock to protect the pile tip. Pile points can be accepted by certification and should be checked to see that they meet the specification requirements.
 
  
Experience has shown that corrosion of this type pile is usually not a serious problem. They must be protected for a short distance below ground level by painting as required by Standard Specification [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.8].
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There are two types of piles generally used by MoDOT. They are structural steel HP pile and close-ended pipe pile (cast-in-place, CIP). Open ended pipe pile (cast-in-place, CIP) can also be used. Structural steel piling are generally referred to as HP piling and two different standard AISC shapes are typically utilized: HP12 x 53 and HP14 x 73. Concrete piling are generally referred to as cast-in-place or CIP piling because the concrete is poured and cast in steel shells which are driven first or pre-driven.  
  
===702.1.3 Test Piles (Sec 702.2.5)===
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===702.1.1 Cast-In-Place (CIP) Concrete Piles ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 702.2.1])===
On structures that have unusually large quantities of piling, pile load tests are often specified. Such test loads are required by governing design specifications which limit maximum loads based on dynamic tests. For structural steel piles, where test loads are specified, the maximum 2006 design load is limited to 6.0 tons per in<sup>2</sup> unless test loads indicate that design loads must be reduced or the footing redesigned to redistribute the loads to a lesser 4.5 tons per in<sup>2</sup>.
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All CIP piles shall be galvanized in accordance with Sec 702 unless otherwise shown on the plans.
  
The pile to be load tested in a point bearing situation is normally driven to refusal on rock
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CIP concrete piling consist of pre-driven steel shells later filled with concrete. The most commonly used type of steel pipe is spirally welded steel sometimes referred to as pipe pile. All steel pipes must be in accordance with ASTM A 252 Grade 3. CIP pile normally has no internal steel reinforcing bars. Steel shells are usually driven without a mandrel if shell thickness is adequate.  
or shale. A friction pile to be test loaded is normally driven to a formula bearing as close as possible to design bearing value but only after a specified minimum tip elevation has been reached.
 
  
The purpose of test loading is to check effectiveness of the pile hammer and dynamic pile
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For CIP pile, Geotechnical Section indicates either "No Pile Point Needed" or "Pile Point Needed" and recommends pile point type on boring log. “Cruciform” or “Conical” pile point reinforcement is allowed for closed ended CIP pile. “Manufactured open ended cutting shoe (inside flange)” pile point reinforcement is allowed for open ended CIP. Generally pile point reinforcement is needed for CIP pile if boulders, cobbles or dense gravel are anticipated.  
formula used. The load test assures a minimum safety factor of 2 based on a maximum allowable
 
permanent set 1/4 in.
 
  
The contractor is generally required to submit in detail the proposed method of load testing.
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Where steel shells are driven, boulders or other obstructions quite often deflect the pipe from their intended course. This problem is worsened if piles are driven on a batter and could result in bent or crushed shells. Steel shells shall hold the original form without distortion after being driven or after adjacent shells have been driven and shall be free from water, soil and other deleterious matter when concrete is cast in the shells. Any shell that has been bent or damaged should be carefully reviewed. In this case, any decision to allow use of bent or damaged shells should be with approval of the Bridge Division and the Construction and Materials Division.  
The proposal should include arrangement of hold down piles if they are to be used. If hold
 
down pile are impractical, it may be necessary to use a direct static load.
 
  
Hydraulic jacks are normally used to apply and measure load to the tested pile. Deformation
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Concrete should be directed down the center of the shell. Concrete hitting the sides of the shell can cause segregation. If concrete can be successfully directed down the center of the shell, a tremie is not required regardless of the height of fall.
and settlement of the loaded pile are recorded by dial gauges which record to the thousandth
 
of an inch. To ensure accuracy these gauges, backed with fixed wires, must be supported so as to
 
be completely independent of the loading system. Methods of measuring uplift on hold down
 
pile should be required. Load increments are applied in accordance with contract requirements.
 
These increments are recorded in the inspector's field book.
 
  
The special provisions establish the load increments, the application intervals, and the
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===702.1.2 Structural Steel Piles (HP) (Sec 702.2.2)===
maximum load to be applied. After the maximum load is applied for a specified time, the load is
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All structural steel HP piles shall be galvanized in accordance with Sec 702 unless otherwise shown on the plans. Structural steel piles are rolled “H”-Sections, often called H-Piles or HP piles, which comes from the AISC designation “HP”, which are used in certain types of pile installations. This type of pile is probably the most widely used in the State of Missouri. HP piles can penetrate into the ground and transmit loads from footings or bent caps to bearing stratum as columns. They displace a small volume of soil and can be driven with relatively close spacing. Pile point reinforcement shall be required for all HP piles required to be driven to bear on rock regardless of pile strength used for design loadings or geomaterial (soils with or without gravel or cobbles) to be penetrated. Pile points can be accepted by certification and should be checked to see that they meet the specification requirements.
released in specified increments and intervals. The test pile load data should be plotted and
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reported in graphic form. Contact the Division of Construction and Materials for assistance in
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===702.1.3 Probe Piles and Static Load Test Piles===
preparing test pile graphs. The elastic shortening of the pile may be computed by the formula:
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<u>Nomenclature</u>
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There two different types of pile testing:
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:* Probe Pile (formerly “Test Pile”)
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:* Static Load Test Pile
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Earlier editions of the Missouri Standard Specifications and AASHTO Specifications referred to probe piles as "test piles". Probe piles are designed to test how a pile goes into the ground by probing the ground, in a sense, but can also proof the ground capacity. It is a description of pile driving (and proof capacity secondarily).
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Static load testing is designed to test the ground capacity, but can also test how a pile goes into the ground.
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So while a probe pile tests (proofs) the pile and pile driving primarily to determine lengths, the static load tests establish pile nominal axial compressive resistance or ground capacity primarily where ground capacities are inadequate using dynamic testing, wave equation analysis or FHWA-modified Gates dynamic pile formula .
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====702.1.3.1 Probe Piles====
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Probe piles are piles driven on site to determine driving conditions, verify hammer size and impact energy, determine pile order lengths and pile driving criteria. More than likely, probe piles, or test piles as they were called were popular and only used when the Department was driving precast or prestressed concrete piles when pile order length was more critical.
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Probe piles (formerly called "test" piles) and their use are described in the Standard Specifications. Probe piles are only required when designated on the bridge plans with a pay item.  Locations for probe piles may be given on the bridge plans or the absence of which means that it is deferred to the discretion of the Engineer.
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Probe piles are good for jobs where there are an unusually large number of piles, or anticipated unusual site or ground conditions, i.e. nonuniform or varying.
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====702.1.3.2 Static Load Test Pile====
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Static load test piles are typically described for use in a Bridge Special Provision, and they are only required when designated on the bridge plans with a pay item.
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Static pile load tests (also referred to as just "load test piles") are piles driven to a pre-determined penetration and then tested by applying static loads incrementally until either proof of load or failure occurs. A pile load test pile can be used as a probe pile in the sense that they are usually performed on site and driven by dynamic testing or FHWA-modified Gates dynamic pile formula, and then static load tested. Therefore, information can be determined about driving conditions, hammer sizing, pile lengths and pile driving criteria.
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On structures that have unusually large quantities of piling, pile load tests may be specified. Such test loads are required by governing design specifications which limit maximum loads based on dynamic tests. For structural steel piles, where test loads are specified, the maximum 2006 design load is limited to 6.0 tons per square inch unless test loads indicate that design loads must be reduced or the footing redesigned to redistribute the loads to a lesser 4.5 tons per square inch.
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The pile to be load tested in a point bearing situation is normally driven to refusal on rock or shale. A friction pile to be load tested is normally driven to a dynamic tested resistance as close as possible to the plan value of the minimum nominal axial compressive resistance, but only after a specified minimum tip elevation has been reached.
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The purpose of load testing is to check effectiveness of the pile hammer and pile dynamic testing used. The load test assures the pile capacity is greater than the minimum nominal axial compressive resistance shown on the plans based on a maximum allowable permanent set 1/4 inch. If the pile capacity is inadequate, then pile shall be redesigned.
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The contractor is generally required to submit in detail the proposed method of load testing. The proposal should include arrangement of hold down piles, if they are to be used. If hold down piles are impractical, it may be necessary to use a direct static load.
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Hydraulic jacks are normally used to apply and measure load to the load-tested pile. Deformation and settlement of the loaded pile are recorded by dial gauges which record to the thousandth of an inch. To ensure accuracy, these gauges, backed with fixed wires, must be supported so as to be completely independent of the loading system. Methods of measuring uplift on hold down pile should be required. Load increments are applied in accordance with contract requirements. These increments are recorded in the inspector's field book.
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The Bridge Special Provision establishes the load increments, the application intervals, and the maximum load to be applied. After the maximum load is applied for a specified time, the load is released in specified increments and intervals. The load test pile data should be plotted and reported in graphic form. Contact the Construction and Materials Division for assistance in preparing test pile graphs. The elastic shortening of the pile may be computed by the formula:
  
 
:<math>E_s = \frac{PL}{AE}</math>
 
:<math>E_s = \frac{PL}{AE}</math>
Line 55: Line 78:
 
:L = Entire length of test pile, in.
 
:L = Entire length of test pile, in.
 
:A = Area of cross-section of pile, in<sup>2</sup>
 
:A = Area of cross-section of pile, in<sup>2</sup>
:E = Modulus of elasticity, usually 29 x 106, lbs/in<sup>2</sup>
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:E = Modulus of elasticity, usually 29 x 10<sup>6</sup>, lbs/in<sup>2</sup>
  
Elastic shortening of any pile can usually be correlated with rebound, measured when the test pile is unloaded. Test pile data, log of readings, and test pile loading graphs should be
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Elastic shortening of any pile can usually be correlated with rebound, measured when the load test pile is unloaded. Load test pile data, log of readings, and load test pile loading graphs should be submitted to the Construction and Materials Division in a form which is neat, legible, and which can be reproduced. Copies of these reports prepared by Construction and Materials Division are submitted to Bridge Division and, if it is an interstate project, to the Federal Highway Administration.
submitted to the Division of Construction and Materials in a form which is neat, legible, and
 
which can be reproduced. Copies of these reports prepared by Division of Construction and
 
Materials are submitted to Bridge Division and, if it is an interstate project, to the Federal Highway Administration.
 
  
 
===702.1.4 Pile Driving===
 
===702.1.4 Pile Driving===
In some instances pre-boring is required as outlined in [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.3.] Where pre-boring is required the hole shall be of a diameter not less than that of the pile and shall be large enough to avoid damage to the pile in driving through the hole into hard material. Good practice requires driving equipment capable of driving piles to necessary depth and bearing without materially damaging the piles. Heavier piles require heavier equipment, with a ratio of ram weight to pile weight sufficient to minimize energy loss due to inertia. The contractor selects equipment to meet specified energy requirements, but the inspector should be familiar with power plant, hammer, cap, cushion block, leads, and other elements used in driving. Each resident engineer may obtain data for hammers from publications issued by the individual equipment manufacturer. The contractor should have bulletins available for equipment he is using.
 
  
Pile hammers are classified by type. There are steam and air hammers, both single acting and double acting. Diesel pile hammers may be either open or enclosed ram types. A differential
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====702.1.4.1 Hammer Types====
hammer is a double acting type. Design loads, size of pile, soil conditions, etc., establish the
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Good practice requires driving equipment capable of driving piles to the necessary penetration and nominal axial compressive resistance without damaging the piles at the pile point, top of the pile or bending piles. Heavier piles may require heavier equipment due to greater nominal axial compressive resistance requirements. When specified in the contract documents, contractors shall perform a drivability analysis to select an appropriate hammer size to ensure the pile can be driven without overstressing the pile and to prevent refusal of the pile prior to reaching the minimum tip elevation. Contractors shall plan their pile driving activities and submit hammer size and hammer energy requirements to the engineer for approval before driving. Contractors select equipment with adequate hammer requirements to drive the pile successfully, and the inspector should be familiar with power plant, hammer, cap, cushion block, leads, and other elements used in driving. Each resident engineer may obtain data for hammers from publications issued by the individual equipment manufacturer. The contractors should have bulletins available for equipment they are using.
choice of hammer. Plans set out minimum energy requirements for individual pile size and for
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each substructure unit.
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Pile hammers are classified by type. There are steam and air hammers, both single acting and double acting. Diesel pile hammers may be either open or enclosed ram types. A differential hammer is a double acting type. Design loads, size of pile, soil conditions, etc., establish the choice of hammer. The contractor shall determine minimum hammer energy requirements for individual pile size and for each substructure unit.
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<u>Single Acting Hammer</u>
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A single acting hammer is one in which the ram is raised by steam, air, or diesel explosion and allowed to drop, with gravity as the only downward force. The energies listed in the manufacturer's bulletins are striking energies rated in accordance with commonly accepted practice. The energy is based upon normal stroke, but does not make allowances for any losses occurring in the hammer, itself, such as back-pressure, friction, or loss within the cushion block.
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With insufficient lift pressure, the ram will not ascend the proper height. In fact, the hammer does not have to ascend through a full stroke to operate. The inspector should check the hammer when testing for resistance and determine if the hammer is operating at its specified number of blows per minute and at the prescribed or recommended pressure. If it is not, energy should be obtained by measuring actual stroke while hammer operates and multiplying actual length of stroke by weight of striking part. The additional distance through which the ram drops, while still in contact with the pile after impact, is not ordinarily taken into account. Neither is "cushion block" loss.
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During easy driving with a smaller blowcount (large set per blow) a reduction in number of blows per minute may occur. Consequently, the hammer stroke while measurable may not be accurate since the hammer/pile is moving downward with the stroke increasing stroke height.
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<u>Double Acting Hammer</u>
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A double acting hammer is one in which steam or air pressure raises the ram then accelerates the down stroke. The differential acting hammer is a type of double acting hammer which provides additional pressure to the ram during the downward stroke.  
  
A '''single acting hammer''' is one in which the ram is raised by steam, air, or diesel explosion and allowed to drop, with gravity as the only downward force. The energies listed in the manufacturer's bulletins are striking energies rated in accordance with commonly accepted practice. The energy is based upon normal stroke but does not make allowances for any losses occurring in the hammer, itself, such as back-pressure, friction, or loss within the cushion block.
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The foot-pounds of energy for a double acting hammer is dependent upon the number of strokes per minute produced with a given steam or air pressure. For example, a typical table of "actual energies" for one commonly used hammer shows that "E" varies from 9500 foot-pounds at 90 strokes per minute up to 13,100 foot-pounds at 105 strokes per minute. The inspector must, for this type hammer, log the number of blows per minute, noting pressure at the hammer, and use the corresponding energies when making a bearing determination by use of the dynamic formula. Refer to manufacturer's bulletins to determine what energies to use for the number of blows per minute. Calculations based on steam or air pressure are misleading because no two setups are identical, and it is impossible to determine the mean effective pressure in the working cylinder from gauge pressure.  
  
With insufficient lift pressure, the ram will not ascend the proper height. In fact, the hammer does not have to ascend through a full stroke to operate. The inspector should check the hammer when testing for bearing and determine if the hammer is operating at its specified number of blows per minute and at the prescribed or recommended pressure. If it is not, energy should be obtained by measuring actual stroke while hammer operates and multiplying actual length of stroke by weight of striking part. The additional distance through which the ram drops, while still in contact with the pile after impact, is not ordinarily taken into account. Neither is
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<u>Diesel Hammer</u>
"cushion block" loss.
 
  
During easy driving with a large set per blow a reduction in number of blows per minute may occur. In consequence, the full theoretical hammer stroke will often not be produced.
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A diesel pile hammer is classed either as a single acting or double acting type. Inspectors should acquaint themselves with the diesel hammer's physical qualities and determine when the hammer is developing full stroke.
  
A '''double acting hammer''' is one in which steam or air pressure raises the ram then accelerates the down stroke. The differential acting hammer is a type of double acting hammer which provides additional pressure to the ram during the downward stroke.
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A diesel hammer is a self-contained unit, including power plant, cylinder, piston, or ram, fuel tank, pump, injectors, and other pertinent parts. The ram of these hammers is raised by explosion of diesel fuel ignited in the cup or anvil of the hammer. Some types of diesel hammers are called double acting hammers. This type of hammer has the ram enclosed. As the ram travels upward, the piston compresses air in the bounce chamber-compressor tank. This compressed air adds to the acceleration of the ram during its downward stroke. It is necessary to use a "Bounce Pressure" gauge on this type of hammer to establish the usable energy for input into the FHWA-modified Gates dynamic pile formula for the nominal axial compressive resistance determination.  
  
The foot-pounds of energy for a double acting hammer is dependent upon the number of strokes per minute produced with a given steam or air pressure. For example, a typical table of "actual energies" for one commonly used hammer shows that "e" varies from 9500 foot-pounds at 90 strokes per minute up to 13,100 foot-pounds at 105 strokes per minute. The inspector must,
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The single acting series of diesel hammers have a "rampiston" which can be partially seen during the upward stroke. If the manufacturer's rated energy is to be used in the FHWA-modified Gates dynamic pile formula then the inspector must determine that the ram is falling through a normal stroke. Failure to operate properly is usually the result of mechanical problems which the contractor must correct. In isolated instances, failure of the hammer to operate with a normal stroke may be caused by the elastic rebound of the pile and bearing material. If the ram is not falling through its usual stroke, the energy "E" used should be the energy which can be calculated from the weight of the ram times the actual stroke through which it falls. The height is determined from the observed exposed length of ram as the ram travels upward.
for this type hammer, log the number of blows per minute, noting pressure at the hammer, and
 
use the corresponding energies when making a bearing determination by use of the dynamic
 
formula. Refer to manufacturer's bulletins to determine what energies to use for the number of
 
blows per minute. Calculations based on steam or air pressure are misleading because no two setups are identical, and it is impossible to determine the mean effective pressure in the working cylinder from gauge pressure.
 
  
The '''Diesel Pile Hammer''' is classed either as a single acting or double acting type. Most states have accepted this hammer with some qualification. Many arbitrarily discount energies set out by the manufacturer, accepting only some percentage of the maximum rated energy. Missouri sets this figure at 75% for single acting diesel hammers. Inspectors should acquaint themselves with the diesel hammer's physical qualities and determine when the hammer is developing full stroke.
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====702.1.4.2 Pile Dynamic Formula====
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MoDOT may specify the use of the FHWA-modified Gates dynamic pile formula (see [https://www.modot.org/missouri-standard-specifications-highway-construction#page=11 Sec 702.4.10]) to calculate pile nominal axial compressive resistance. The [[media:702 Pile Driving Set Calculator R201305.xlsx|Pile Driving Set Calculator]] is a spreadsheet that can be used to calculate the blowcount (N) in blows per inch of pile permanent set (BPI) to determine when to stop driving pile.
  
A diesel hammer is a self contained unit, including power plant, cylinder, piston, or ram,
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====702.1.4.3 Pile Driving Specifics, Special Conditions and Inspection====
fuel tank, pump, injectors, and other pertinent parts. The ram of these hammers is raised by
 
explosion of diesel fuel ignited in the cup or anvil of the hammer. Some types of diesel hammers
 
are called double acting hammers. This type of hammer has the ram enclosed. As the ram travels
 
upward, the piston compresses air in the bounce chamber-compressor tank. This compressed air
 
adds to the acceleration of the ram during its downward stroke. It is necessary to use a "Bounce
 
Pressure" gauge on this type of hammer to establish the usable energy for dynamic formula bearing determination. For this type of diesel hammer, explosive force is not taken into account to determine usable energy. Use of the "gauge energy" permits full use of 2E in the "double acting" bearing formula and energy is not to be discounted to 75%.
 
  
The single acting series of diesel hammers have a "rampiston" which can be partially seen during the upward stroke. If the full "maximum" manufacturer's energy is to be used in the
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<u>Preparation for Pile Driving</u>
specific dynamic formula then the inspector must determine that the ram is falling through a
 
normal stroke. Failure to operate properly is usually the result of mechanical problems which the contractor must correct. In isolated instances, failure of the hammer to operate with a normal stroke may be caused by the elastic rebound of the pile and bearing material. If the ram is not falling through its usual stroke, the energy "E" used should not be the maximum striking energy but the energy which can be calculated from the weight of the ram (W) times the actual stroke (H) through which it falls, or (W x H). The height (H) is determined from the observed exposed length of ram as the ram travels upward. When this method is employed, the energy should not be discounted. Where the energy is measured by W x H, the inspector should use the single acting formula from the specifications. This procedure may not be used to increase the energy allowance above 0.75E.
 
  
====702.1.4.1 Pile Formula====
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:* A qualified inspector shall be assigned continuously on pile driving work to see that each pile is driven to the specified  nominal axial compressive resistance and that all piles are properly located and driven.  
The Missouri Highway and Transportation Department specifies the use the FHWA-Modified Gates equation (See [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.10]) to calculate pile bearing. The [http://modot.mo.gov/business/documents/Pile-Driving-Chart.xls Pile Driving Set Calculator] is a spreadsheet that can be used to calculate the pile set to help determine when to stop driving pile.
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:* The inspector must keep a detailed record of the data for each pile. The record should show for each pile, its position, tip and cut-off diameter (for timber), total length in place, length placed in leads, tip elevation, batter, and number of blows per inch (BPI) at the time driving is stopped.
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:* The number of blows per inch is based on penetration for the last series of 10 to 20 blows per inch.  
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:* The inspector shall record all pertinent information regarding the hammer used so that a review and check of  nominal axial compressive resistance may be made.
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:* Any unusual occurrences or delay during driving shall be recorded.  
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:* When driving friction pile, the inspector shall make periodic  resistance checks as the pile is being driven to know at any time the approximate  nominal axial compressive resistance of the pile if problems should develop.  
  
====702.1.4.2 Inspection====
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<u>Lifting Holes</u>
A qualified inspector should be assigned continuously on pile driving work to see that each pile is driven to specified bearing, that all piles are properly located, and that the required
 
number are driven. The inspector must keep a detailed record of the data for each pile.
 
The record should show for each pile, its position, tip and cut-off diameter (for timber), total
 
length in place, length placed in leads, tip elevation, batter, and number of blows per inch at
 
the time driving is stopped. The number of blows per inch is based on penetration for the last
 
series of 10 to 20 blows. The inspector should record all pertinent information
 
regarding the hammer used so that a review and check of bearing may be made. Any unusual occurrences or delay during driving should be recorded. When driving friction pile, the inspector should make periodic bearing checks as the pile is being driven to know at any time
 
approximate bearing of the pile if problems should develop.
 
  
Contractors that elect to place lifting holes in piling in lieu of using a choker cable may be permitted to do so with the following provisions. The concern of burning lifting holes in piling is that undesirable capacity reductions may occur. Lifting holes would only be permissible provided they would not remain in the piling lengths used for the completed structure. i.e. Lifting holes would need to be in an excess length of end piling which would either be cut off after driving, or in the case of splicing the holed end would be removed before splicing on the next section. Any added risk of buckling or damage to the piling that may result from a weakened cross section during driving is the contractor's responsibility.  
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Contractors that elect to place lifting holes in piling in lieu of using a choker cable may be permitted to do so with the following provisions. The concern of burning lifting holes in piling is that undesirable capacity reductions may occur. Lifting holes would only be permissible provided they would not remain in the piling lengths used for the completed structure, i.e. lifting holes would need to be in an excess length of end piling which would either be cut off after driving, or in the case of splicing the holed end would be removed before splicing on the next section. Any added risk of buckling or damage to the piling that may result from a weakened cross section during driving is the contractor's responsibility.  
  
 
There shall be no additional payment for the additional length of piling to compensate for removing the cut-off ends with the holes.
 
There shall be no additional payment for the additional length of piling to compensate for removing the cut-off ends with the holes.
  
It is good practice for piling in a group or cluster to be driven in sequence which proceeds from the center of the group each way to the outer rows of pile. This will usually avoid uplift
+
<u>Pile Driving in Groups</u>
and loss of bearing in previously driven pile.
+
 
 +
It is good practice for piling in a group or cluster to be driven in sequence which proceeds from the center of the group each way to the outer rows of pile. This will usually avoid uplift and loss of resistance in previously driven pile. For a single row of piles, the sequence should follow end to end or middle to out but never end to middle from both ends.
 +
 
 +
The pile numbering on the As Built Pile Data plan sheet in the bridge plans is a random numbering scheme for the purposes of recording data and unrelated to pile driving sequencing. Just keep track of both numbering schemes to avoid confusion when recording during driving and recording final data on plan sheet.
 +
 
 +
<u>Pile Driving to Soft and Hard Rock</u>
 +
 
 +
In many cases piles are to be driven to rock or shale. The FHWA-modified Gates dynamic pile formula is applicable for soils, hard but penetrable material and soft rock. It is not applicable in hard rock at which point an inspector’s sense of anticipating elevation of hard rock coupled with the physical response of hammer and pile upon nearing and impacting hard rock is critical to properly seating HP piles on hard rock with limited to no pile damage. Since the nominal axial compressive resistance at the time of practical refusal is not an accurate resistance, the inspector should always be aware of the sounding data as the tip of the pile nears anticipated elevations of hard material. The pile should be seated on or into hard material with blows which will not damage the tip of the pile. Each bearing pile should be proofed for "practical refusal" unless it is clearly seated on solid rock.
 +
 
 +
The inspector will find other supplementary notes in the Foundation Data Table which should be taken into consideration for the proper and cautious driving of structural steel piles. It is especially important that  steel HP piles which are to be seated on rock or shale be driven and proofed for "pile refusal" as specified in Sec 702.4.11. When the pile is well seated, the driving should cease. The inspector should record in the diary that the pile has been driven into shale or rock as the case may be. Either record penetration and bearing in the case of practical refusal or note "refusal on rock" in the case of absolute refusal on rock. Such notations will indicate full compliance with pile resistance requirements on the plans.
 +
 
 +
Piles to be driven shall be plainly marked at a distance from the tip equal to the distance from ground line to the elevation shown on the soundings for rock or shale. It is also good practice to mark the pile from the tip equal to the distance from the ground surface down to any layer of boulders, thin rock strata, or other hard or firm material which might cause unusual driving conditions and point resistance. The pile driving foreman or contractor's foreman shall be instructed on the significance of such marks and all personnel shall be instructed accordingly. This procedure will result in fewer damaged piles. The goal is to have no damaged piles.
 +
 
 +
<u>Pile Splices</u>
 +
 
 +
Splices may be required to extend structural steel or steel shell pile to reach adequate nominal axial compressive resistance. No direct payment will be made for splices that are within the plan pile length. Any splices outside of plan length required to achieve resistance will be paid for as an additional 8 feet of pile in place at the contract unit price per authorized splice. Field splices have a greater potential of failure during driving than the original furnished pile. Therefore it is preferable to have a minimum amount of field splicing. [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 702.4.6] states, "Full length piles shall be driven wherever possible and practical." A full length pile should be used unless there is clearance, shipping, excessive cost, or other considerations which would make it impractical.
 +
 
 +
'''Structural Steel HP Pile:'''
 +
:<u>Manufactured Pile Splices</u>
 +
 
 +
:MoDOT has received and approved one type of manufactured pile splicer for use with recommended guidelines. The AFB Champion H-Pile Splicer HP-30000 has been approved. The following are recommended guidelines that should be used beyond the manufacturer’s recommended assembly procedure for the use of the HP-30000 splicers:
 +
 
 +
::1. It would be permissible for non-flexible bent locations only. This would include intermediate bents on pile footings and semi-deep abutments. This splicer system should not be used on flexible bents, such as pile cap intermediate bents, where the concrete beam is supported on a single row of exposed piling or on integral or non-integral end bents.
 +
 
 +
::2. Full penetration groove welds connecting the pile flanges are required. The partial penetration groove welds as recommended by the manufacturer are not acceptable.
 +
 
 +
::3. A 5/16" minimum fillet weld should be added at both ends of the splicer, welded to the pile webs. The length of this weld should be at least 1/2 the depth of the pile. This weld was not a recommendation of the manufacturer. This weld is for additional safety in the event that the splicer is damaged or torn from being snagged on rock material.
 +
 
 +
'''Cast-In-Place Concrete Piles (CIP):'''
 +
 
 +
For splice details, see:
 +
 
 +
<center>
 +
{| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center"
 +
|+
 +
| style="background:#BEBEBE" width="400" |'''[http://www.modot.org/business/consultant_resources/bridgestandards.htm Bridge Standard Drawings]'''
 +
|-
 +
|align="center"|[http://www.modot.org/business/standard_drawings2/pile_new_title_block.htm Pile]
 +
|}
 +
 
 +
</center>
 +
 
 +
<u>Pile Inspection</u>
 +
 
 +
The inspector must ensure that all piles have been properly inspected. Piles that are cast-in-place on the job shall be inspected using the same inspection procedures as for any other concrete item. Files should contain any applicable inspection reports on aggregate, cement and reinforcing steel. The concrete Plant Inspector's Report and compressive test reports will serve to document acceptability of piles. Steel shells for cast-in-place piles and structural steel piles are normally inspected by project forces. Inspection should include dimensions, wall thickness of shells, visual inspection of welds, closure plates, etc. The contractor is required to furnish certified mill test reports for the steel. Heat numbers of pile should be checked against heat numbers on the mill test reports. The resident engineer should report the results of inspection on a Fabrication Inspection Report, [[media:712 Fabrication Inspection Report secure.pdf|Form B-708R2]], or an alternate format may be used. A spreadsheet version of the form is available to facilitate the automatic creation of an AASHTOWARE Project (AWP) record for use by the Construction and Materials Division. This information will be retained in the project file with mill test reports attached.
 +
 
 +
<u>Pile Driving and Preboring</u>
 +
 
 +
In some instances preboring is required as outlined in [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 702.4.3]. Preboring can be required on the bridge plans:
 +
 
 +
:1. When there is more than five ft. of embankment that has been in place less than five years to avoid buildup of downdrag forces (called negative skin friction)
 +
 
 +
:2. When hard material must be penetrated to meet minimum tip elevation requirements
 +
 
 +
:3. When oversized holes in hard material or rock must be constructed to allow lateral pile movement
 +
 
 +
In any case, the requirement for preboring will be noted on the bridge plans for each pile with an elevation given for depth of preboring which is used to estimate and check proposed preboring quantities on the plans.
 +
 
 +
For prebored holes not in hard rock, holes shall be filled with sand or other approved materials either prior to or after pile placement. For prebored holes in hard rock, holes shall be filled with sand or other approved materials prior to pile placement. Filling the hole with sand first will condense sand and stabilize pile while driving on hard rock. The driving criteria for driving piling on hard rock shall be the same as given in [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 702.4.11].
 +
 
 +
Where pre-boring is required the hole shall be of a diameter not less than that of the pile unless oversized as explained previously and shall be large enough to avoid damage to the pile in driving through the hole when in soft or hard material including rock.
  
In many cases piles are to be driven to rock or shale. The FHWA-Modified Gates equation, designed for friction pile, is not altogether applicable in these circumstances. Since the bearing value at the time of practical refusal is not an accurate bearing resistance figure, the inspector should keep the sounding data well in mind as the tip of the pile nears anticipated elevations of hard material. The pile should be seated on or into hard material with blows which will not damage the tip of the pile. Each bearing pile should be tested for "practical refusal" unless it is clearly seated on solid rock.
+
Caution is warranted when driving piling in prebored holes in hard rock. Pile instability is increased because of initially loose sand condition. Absence of more stabilizing stiffer soils and hard material over rock that can act to reduce bending and buckling can cause more pile spring and bounce. Pile point damage is at increased levels of risk because proofing rock in excess of driving criteria given for driving piling on hard rock can be greater since there is only loose sand acting in friction along the sides of the pile which if compacted would normally tend to dissipate energy as the impact wave travels down the pile. This is why sand is placed in the hole prior to pile placement in order to increase the frictional condition while increasing buckling stability of the pile.
  
The inspector should examine the plans carefully for changes in hammer requirements. For structural steel piles, for example, the pile data table on the bridge plans specify minimum energy requirements for a pile hammer for each individual substructure unit. Under the pile data
+
====702.1.4.4 DFI Documents on Pile Driving and Hammers====
table, the inspector will find other supplementary notes which should be taken into consideration for proper driving of structural steel piles. It is especially important that such piles which are to be seated on rock or shale be driven and tested for "practical refusal" as specified in [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.11.] When the pile is well seated, the driving should cease. The inspector should record in the diary that the pile has been driven into shale or rock as the case may be. Either record penetration and bearing in the case of practical refusal or note "refusal on rock" in the case of absolute refusal on rock. Such notations will indicate full compliance with bearing requirements of the plans.
 
  
Piles to be driven should be plainly marked at a distance from the tip equal to the distance
+
Deep Foundations Institute (DFI) produced and published two critical documents in 1979 and then republished them in 1995 and 1997 related to pile hammers and pile driving. Copies of these documents were purchased from DFI and permission was granted by them for making these documents available on-line to MoDOT personnel only. The document links will not be available to external users outside MoDOT IS network environment.
from ground line to the elevation shown on the soundings for rock or shale. It is also good practice to mark the pile from the tip equal to the distance from the ground surface down to any layer of boulders, thin rock strata, or other hard or firm material which might cause unnatural point resistance or unusual driving conditions. The pile driving foreman or contractor's foreman should be told the significance of such marks and all personnel should be guided accordingly. This procedure will result in fewer broken, "broomed", or damaged piles.  
 
  
Splices may be required to extend structural steel or steel shell pile to reach adequate bearing. No direct payment will be made for splices that are within the plan pile length. Any splices outside of plan length that are required to achieve bearing will be paid for as an additional 8 feet of pile in place at the contract unit price, per authorized splice.
+
These documents are provided for further guidance and understanding of pile driving and equipment. They do not reflect the policy of MoDOT, but can be used to support and reinforce decisions involving pile driving and equipment since the background and source of this information is time tested and produced by a reputable organization.
  
Field splices have a greater potential of failure during driving than the original furnished
+
'''(1) [https://modotgov.sharepoint.com/sites/br/Shared%20Documents/Forms/AllItems.aspx?id=%2Fsites%2Fbr%2FShared%20Documents%2FEPG%20Links%2FBook%5F25%5FInspectors%5FManual%5FFor%5FDriven%5FPile%5FFoundations%2Epdf&parent=%2Fsites%2Fbr%2FShared%20Documents%2FEPG%20Links Deep Foundations Institute (DFI), Inspector’s Manual for Driven Pile Foundations, 2nd Ed. 1997. Englewood Cliffs, New Jersey]'''
pile. Therefore it is preferable to have a minimum amount of field splicing. [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.6] states, "Full length piles shall be driven wherever possible and practical." A full-length pile should be used unless there is clearance, shipping, excessive cost, or other considerations, which make it impractical.
 
  
The inspector must ensure that all piles have been properly inspected. Precast concrete pile will normally have been inspected during casting and curing by the Division of Construction
+
<u>Information</u> published within this main document:
and Materials. In such cases, they will provide the resident engineer with proper inspection
 
reports. If the piles are cast on the project, they will, of course, be inspected the same as any other concrete item. Files should contain any applicable inspection reports on aggregate, cement and reinforcing steel. The concrete Plant Inspector's Report and compressive test reports will serve to document acceptability of piles. This would also be true for concrete in cast-in-place piles. Steel shells for cast-in-place piles and structural steel piles are normally inspected by project forces. Inspection should include dimensions, wall thickness of shells, visual inspection of welds, closure plates, etc. The contractor is required to furnish certified mill test reports for the steel. Heat numbers of pile should be checked against heat numbers on the mill test reports. The resident engineer reports results of inspection on a Fabrication Inspection Report, [[media:712 Fabrication Inspection Report.gif|Form B-708R2]], or the equivalent data may be recorded in an alternate format. A spreadsheet version of the form is available to facilitate the automatic creation of a SiteManager record for use by the Division of Construction and Materials. This information will be retained in the project file with mill test reports attached.
 
  
====702.1.4.3 Manufactured Pile Splices====
+
:* Provides Information on soil investigation, the various pile types, pile driving by impact methods, pile tests, pile dynamic testing and analysis, static load testing, pile hammers and pile driving machinery and ancillary equipment
To date MoDOT has been submitted one type of manufactured pile splicer and approved it for use with certain stipulations. The AFB Champion H-Pile Splicer HP-30000 has been approved. The following are recommended guidelines that should be used beyond the manufacturers recommended assembly procedure for the use of the HP-30000 splicers.
+
:* Explains increases in driving resistance with depth in uniform soils
 +
:* Explains driving resistance as a function of N-values
 +
:* Explains changes in driving resistance as soil layers change
 +
:* Explains pile markings, finer increments and how these are effectively used
 +
:* Provides good description of scenarios when blowcounts are changing
 +
:* Provides basic rules to be followed DURING driving and when approaching termination
 +
:* Provides guidance on termination criteria
 +
:* Provides explanation of pile dynamic testing
 +
:* Provides explanation of static load testing (which we have been doing lately because of Missouri University of Science and Technology research project)
 +
:* Written from the perspective of the pile inspector and presents advice as to the inspector's role and responsibilities in the pile installation and quality assurance processes
 +
:* Provides invaluable training for inexperienced Inspectors and a useful reference guide for the experienced inspector or crew member.
  
:1. It would be permissible for non-flexible bent locations only. This would include intermediate bents on pile footings and semi-deep abutments. This splicer system should not be used on flexible bents, such as pile cap intermediate bents, where the concrete beam is supported on a single row of exposed piling nor on integral or non-integral end bents.
+
'''(2) [https://modotgov.sharepoint.com/sites/br/Shared%20Documents/Forms/AllItems.aspx?id=%2Fsites%2Fbr%2FShared%20Documents%2FEPG%20Links%2FBook%5F24%5FPile%5FInspectors%5FGuide%5FTo%5FHammers%2Epdf&parent=%2Fsites%2Fbr%2FShared%20Documents%2FEPG%20Links Deep Foundations Institute (DFI), A Pile Inspector’s Guide to Hammers, 2nd Ed. 1995. Springfield, New Jersey]'''
  
:2. Full penetration groove welds connecting the pile flanges are required. The partial penetration groove welds as recommended by the manufacturer are not acceptable.
+
<u>Information</u> published within this companion document:
  
:3. A 5/16" minimum fillet weld should be added at both ends of the splicer, welded to the pile webs. The length of this weld should be at least 1/2 the depth of the pile. This weld was not a recommendation of the manufacturer. This weld is for additional safety in the event that the splicer is damaged or torn from being snagged on rock material.
+
:* Explains fundamentals of hammer efficiency and hammer measurement
 +
:* Provides basic information about hammer types
 +
:* Provides operational conformance <u>checklists</u> for inspectors for each hammer type
 +
:* Provides possible helpful suggestions for troubleshooting and what an inspector can offer to the pile crew in assisting them.
  
 
===702.1.5 Pile Driving Documentation===
 
===702.1.5 Pile Driving Documentation===
The inspector should record in detail all important facts regarding driving of each pile. The field book notes should be organized in a sequence similar to that shown in the [[Media:702 Pile Driving Worksheet.pdf|Pile Driving Worksheet]].
+
The inspector should record in detail all important facts regarding driving of each pile. The field book notes should be organized in a sequence similar to that shown in the [[Media:702 Pile Driving Worksheet secure.pdf|Pile Driving Worksheet]].
  
The sample form in the [[Media:702 Pile Driving Worksheet.pdf|Pile Driving Worksheet]] illustrates a typical page of completed pile driving data for pre-cast concrete pile. Data in a similar form will be filled out when driving timber pile.
+
The sample form in the [[Media:702 Pile Driving Worksheet secure.pdf|Pile Driving Worksheet]] illustrates a typical page of completed pile driving data for cast-in-place concrete pile. Data in a similar form will be filled out when driving structural steel pile.
  
[[Figure 700.2]] is an illustration of field book data for driving structural steel pile. The
+
[[media:702 secure.pdf|Figure 702]] is an illustration of field book data for driving structural steel pile. The inspector records the actual length used and notes the number of pieces incorporated in the length. When structural steel pile is driven, there is often a piece left over from the in-place pile which becomes excess or left-over pile. The contractor may wish to use such a piece on another state highway project. If transfer to another project is desired, extra copies of the certified mill test reports should be made which can be used to have the excess pile reinspected on a future project.
inspector records the actual length used and notes the number of pieces incorporated in the
 
length. When structural steel pile is driven, there is often a piece left over from the in-place pile which becomes excess or left-over pile. The contractor may wish to use such a piece on another state highway project. If transfer to another project is desired, extra copies of the certified mill test reports should be made which can be used to have the left over pile reinspected on a future project.
 
  
If test pile is a contract item, it must be driven to specified minimum tip elevation regardless
+
<u>Probe Pile</u>
of the bearing achieved. After this elevation is reached, driving must continue until one of
 
the following three conditions has been met:
 
  
:l. The pile driven to full length.
+
If probe pile is a contract pay item, it must be driven to specified minimum tip elevation regardless of the nominal axial compressive resistance achieved. After this elevation is reached, driving must continue until one of the following three conditions has been met:  
:2. The pile driven to refusal.
 
:3. The pile driven to a capacity 50 percent greater than plan bearing.
 
  
These conditions are specified in [http://modot.mo.gov/business/standards_and_specs/Sec0702.pdf Sec 702.4.1.] It is important that a complete driving log be developed. The pile should be marked off in foot increments. The driving record should then show the number of blows for each foot. Some arrangement is necessary to check number of blows per foot without stopping the driving. If there is a sudden sharp change in the number of blows for a given penetration, it may be necessary to check bearing for intermediate increments to develop an accurate graph. The results of specified test pile driving are to be reported on Test Pile Data form. Contact the Division of Construction and Materials for assistance in reporting test pile data.
+
:l. The pile is driven to full length
  
==702.2 Laboratory Procedures for Sec 702==
+
:2. The pile is driven to refusal
This establishes procedures for Laboratory testing and reporting samples of steel strand used in precast-prestressed concrete piles.
 
  
===702.2.1 Procedure===
+
:3. The pile is driven to a capacity 50 percent greater than plan minimum nominal axial compressive resistance.
Tests for stress-relieved strand shall consist of examination for fabrication requirements and tension tests performed according to AASHTO M203. Test results and calculations shall be recorded through SiteManager.
 
  
===702.2.2 Sample Record===
+
These conditions are specified in [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 702.4.1.] It is important that a complete driving log be developed. The pile should be marked off in foot increments. The driving record should then show the number of blows for each foot. Some arrangement is necessary to check number of blows per foot without stopping the driving. If there is a sudden sharp change in the number of blows for a given penetration, it may be necessary to check resistance for intermediate increments to develop an accurate graph. The results of specified probe pile driving are to be reported on Probe Pile Data form. Contact the Construction and Materials Division for assistance in reporting probe pile data.
The sample record shall be completed in SiteManager as described in [http://contribute.modot.mo.gov/business/materials/pdf/vol_3/AS3510.pdf Automation Section 3510] and shall indicate acceptance, qualified acceptance, or rejection. Appropriate remarks, as described in [[106.20 Reporting|EPG 106.20 Reporting]], are to be included in the remarks to clarify conditions of acceptance or rejection. Test results shall be reported on the appropriate templates under the Tests tab.
 

Latest revision as of 09:25, 27 June 2022

This article contains information about piling types and pile driving criteria used by Construction and Materials Division for on-site pile and pile driving inspection purposes (in the field). This information was part of the former Field Inspection Guidance of the Construction and Materials Manual (see EPG 106 Control of Materials) and is continually updated.

Pile Driving Set Calculator

702.1 Pile Types and Testing

The principal function of piles is to transmit loads which cannot be adequately supported at normal footing levels, to a depth where adequate support is available.

When a pile passes through poor material and its tip penetrates a small distance into a sound stratum of good bearing capacity, it is called a bearing pile. The material which is penetrated may vary all the way from water to materials that would ordinarily serve to support surface footings, but cannot be used because of severe settlement restrictions.

When a pile extends part way through deep strata of limited supporting resistance and capacity is developed primarily from surface friction along the sides of the pile with some end bearing, the pile is generally referred to as a friction pile. A type of pile normally used as a friction pile is a cast-in-place concrete pile(CIP pile).

A battered pile is a pile driven on an inclination (a sloping position) to aid in resisting horizontal loads.

Piles utilized as part of concrete footings where the piles are below the finished ground are referred to as foundation piles. The pile-footing system is generally referred to as a pile cap footing. Piles which support bent caps are called trestle piles and the pile-bent system is generally referred to as a pile cap bent.

Pile types are specified on the bridge plans.

There are two types of piles generally used by MoDOT. They are structural steel HP pile and close-ended pipe pile (cast-in-place, CIP). Open ended pipe pile (cast-in-place, CIP) can also be used. Structural steel piling are generally referred to as HP piling and two different standard AISC shapes are typically utilized: HP12 x 53 and HP14 x 73. Concrete piling are generally referred to as cast-in-place or CIP piling because the concrete is poured and cast in steel shells which are driven first or pre-driven.

702.1.1 Cast-In-Place (CIP) Concrete Piles (Sec 702.2.1)

All CIP piles shall be galvanized in accordance with Sec 702 unless otherwise shown on the plans.

CIP concrete piling consist of pre-driven steel shells later filled with concrete. The most commonly used type of steel pipe is spirally welded steel sometimes referred to as pipe pile. All steel pipes must be in accordance with ASTM A 252 Grade 3. CIP pile normally has no internal steel reinforcing bars. Steel shells are usually driven without a mandrel if shell thickness is adequate.

For CIP pile, Geotechnical Section indicates either "No Pile Point Needed" or "Pile Point Needed" and recommends pile point type on boring log. “Cruciform” or “Conical” pile point reinforcement is allowed for closed ended CIP pile. “Manufactured open ended cutting shoe (inside flange)” pile point reinforcement is allowed for open ended CIP. Generally pile point reinforcement is needed for CIP pile if boulders, cobbles or dense gravel are anticipated.

Where steel shells are driven, boulders or other obstructions quite often deflect the pipe from their intended course. This problem is worsened if piles are driven on a batter and could result in bent or crushed shells. Steel shells shall hold the original form without distortion after being driven or after adjacent shells have been driven and shall be free from water, soil and other deleterious matter when concrete is cast in the shells. Any shell that has been bent or damaged should be carefully reviewed. In this case, any decision to allow use of bent or damaged shells should be with approval of the Bridge Division and the Construction and Materials Division.

Concrete should be directed down the center of the shell. Concrete hitting the sides of the shell can cause segregation. If concrete can be successfully directed down the center of the shell, a tremie is not required regardless of the height of fall.

702.1.2 Structural Steel Piles (HP) (Sec 702.2.2)

All structural steel HP piles shall be galvanized in accordance with Sec 702 unless otherwise shown on the plans. Structural steel piles are rolled “H”-Sections, often called H-Piles or HP piles, which comes from the AISC designation “HP”, which are used in certain types of pile installations. This type of pile is probably the most widely used in the State of Missouri. HP piles can penetrate into the ground and transmit loads from footings or bent caps to bearing stratum as columns. They displace a small volume of soil and can be driven with relatively close spacing. Pile point reinforcement shall be required for all HP piles required to be driven to bear on rock regardless of pile strength used for design loadings or geomaterial (soils with or without gravel or cobbles) to be penetrated. Pile points can be accepted by certification and should be checked to see that they meet the specification requirements.

702.1.3 Probe Piles and Static Load Test Piles

Nomenclature There two different types of pile testing:

  • Probe Pile (formerly “Test Pile”)
  • Static Load Test Pile

Earlier editions of the Missouri Standard Specifications and AASHTO Specifications referred to probe piles as "test piles". Probe piles are designed to test how a pile goes into the ground by probing the ground, in a sense, but can also proof the ground capacity. It is a description of pile driving (and proof capacity secondarily).

Static load testing is designed to test the ground capacity, but can also test how a pile goes into the ground.

So while a probe pile tests (proofs) the pile and pile driving primarily to determine lengths, the static load tests establish pile nominal axial compressive resistance or ground capacity primarily where ground capacities are inadequate using dynamic testing, wave equation analysis or FHWA-modified Gates dynamic pile formula .

702.1.3.1 Probe Piles

Probe piles are piles driven on site to determine driving conditions, verify hammer size and impact energy, determine pile order lengths and pile driving criteria. More than likely, probe piles, or test piles as they were called were popular and only used when the Department was driving precast or prestressed concrete piles when pile order length was more critical.

Probe piles (formerly called "test" piles) and their use are described in the Standard Specifications. Probe piles are only required when designated on the bridge plans with a pay item. Locations for probe piles may be given on the bridge plans or the absence of which means that it is deferred to the discretion of the Engineer.

Probe piles are good for jobs where there are an unusually large number of piles, or anticipated unusual site or ground conditions, i.e. nonuniform or varying.

702.1.3.2 Static Load Test Pile

Static load test piles are typically described for use in a Bridge Special Provision, and they are only required when designated on the bridge plans with a pay item.

Static pile load tests (also referred to as just "load test piles") are piles driven to a pre-determined penetration and then tested by applying static loads incrementally until either proof of load or failure occurs. A pile load test pile can be used as a probe pile in the sense that they are usually performed on site and driven by dynamic testing or FHWA-modified Gates dynamic pile formula, and then static load tested. Therefore, information can be determined about driving conditions, hammer sizing, pile lengths and pile driving criteria.

On structures that have unusually large quantities of piling, pile load tests may be specified. Such test loads are required by governing design specifications which limit maximum loads based on dynamic tests. For structural steel piles, where test loads are specified, the maximum 2006 design load is limited to 6.0 tons per square inch unless test loads indicate that design loads must be reduced or the footing redesigned to redistribute the loads to a lesser 4.5 tons per square inch.

The pile to be load tested in a point bearing situation is normally driven to refusal on rock or shale. A friction pile to be load tested is normally driven to a dynamic tested resistance as close as possible to the plan value of the minimum nominal axial compressive resistance, but only after a specified minimum tip elevation has been reached.

The purpose of load testing is to check effectiveness of the pile hammer and pile dynamic testing used. The load test assures the pile capacity is greater than the minimum nominal axial compressive resistance shown on the plans based on a maximum allowable permanent set 1/4 inch. If the pile capacity is inadequate, then pile shall be redesigned.

The contractor is generally required to submit in detail the proposed method of load testing. The proposal should include arrangement of hold down piles, if they are to be used. If hold down piles are impractical, it may be necessary to use a direct static load.

Hydraulic jacks are normally used to apply and measure load to the load-tested pile. Deformation and settlement of the loaded pile are recorded by dial gauges which record to the thousandth of an inch. To ensure accuracy, these gauges, backed with fixed wires, must be supported so as to be completely independent of the loading system. Methods of measuring uplift on hold down pile should be required. Load increments are applied in accordance with contract requirements. These increments are recorded in the inspector's field book.

The Bridge Special Provision establishes the load increments, the application intervals, and the maximum load to be applied. After the maximum load is applied for a specified time, the load is released in specified increments and intervals. The load test pile data should be plotted and reported in graphic form. Contact the Construction and Materials Division for assistance in preparing test pile graphs. The elastic shortening of the pile may be computed by the formula:

Where:
Es = Elastic shortening, in.
P = Load, lbs
L = Entire length of test pile, in.
A = Area of cross-section of pile, in2
E = Modulus of elasticity, usually 29 x 106, lbs/in2

Elastic shortening of any pile can usually be correlated with rebound, measured when the load test pile is unloaded. Load test pile data, log of readings, and load test pile loading graphs should be submitted to the Construction and Materials Division in a form which is neat, legible, and which can be reproduced. Copies of these reports prepared by Construction and Materials Division are submitted to Bridge Division and, if it is an interstate project, to the Federal Highway Administration.

702.1.4 Pile Driving

702.1.4.1 Hammer Types

Good practice requires driving equipment capable of driving piles to the necessary penetration and nominal axial compressive resistance without damaging the piles at the pile point, top of the pile or bending piles. Heavier piles may require heavier equipment due to greater nominal axial compressive resistance requirements. When specified in the contract documents, contractors shall perform a drivability analysis to select an appropriate hammer size to ensure the pile can be driven without overstressing the pile and to prevent refusal of the pile prior to reaching the minimum tip elevation. Contractors shall plan their pile driving activities and submit hammer size and hammer energy requirements to the engineer for approval before driving. Contractors select equipment with adequate hammer requirements to drive the pile successfully, and the inspector should be familiar with power plant, hammer, cap, cushion block, leads, and other elements used in driving. Each resident engineer may obtain data for hammers from publications issued by the individual equipment manufacturer. The contractors should have bulletins available for equipment they are using.

Pile hammers are classified by type. There are steam and air hammers, both single acting and double acting. Diesel pile hammers may be either open or enclosed ram types. A differential hammer is a double acting type. Design loads, size of pile, soil conditions, etc., establish the choice of hammer. The contractor shall determine minimum hammer energy requirements for individual pile size and for each substructure unit.

Single Acting Hammer

A single acting hammer is one in which the ram is raised by steam, air, or diesel explosion and allowed to drop, with gravity as the only downward force. The energies listed in the manufacturer's bulletins are striking energies rated in accordance with commonly accepted practice. The energy is based upon normal stroke, but does not make allowances for any losses occurring in the hammer, itself, such as back-pressure, friction, or loss within the cushion block.

With insufficient lift pressure, the ram will not ascend the proper height. In fact, the hammer does not have to ascend through a full stroke to operate. The inspector should check the hammer when testing for resistance and determine if the hammer is operating at its specified number of blows per minute and at the prescribed or recommended pressure. If it is not, energy should be obtained by measuring actual stroke while hammer operates and multiplying actual length of stroke by weight of striking part. The additional distance through which the ram drops, while still in contact with the pile after impact, is not ordinarily taken into account. Neither is "cushion block" loss.

During easy driving with a smaller blowcount (large set per blow) a reduction in number of blows per minute may occur. Consequently, the hammer stroke while measurable may not be accurate since the hammer/pile is moving downward with the stroke increasing stroke height.

Double Acting Hammer

A double acting hammer is one in which steam or air pressure raises the ram then accelerates the down stroke. The differential acting hammer is a type of double acting hammer which provides additional pressure to the ram during the downward stroke.

The foot-pounds of energy for a double acting hammer is dependent upon the number of strokes per minute produced with a given steam or air pressure. For example, a typical table of "actual energies" for one commonly used hammer shows that "E" varies from 9500 foot-pounds at 90 strokes per minute up to 13,100 foot-pounds at 105 strokes per minute. The inspector must, for this type hammer, log the number of blows per minute, noting pressure at the hammer, and use the corresponding energies when making a bearing determination by use of the dynamic formula. Refer to manufacturer's bulletins to determine what energies to use for the number of blows per minute. Calculations based on steam or air pressure are misleading because no two setups are identical, and it is impossible to determine the mean effective pressure in the working cylinder from gauge pressure.

Diesel Hammer

A diesel pile hammer is classed either as a single acting or double acting type. Inspectors should acquaint themselves with the diesel hammer's physical qualities and determine when the hammer is developing full stroke.

A diesel hammer is a self-contained unit, including power plant, cylinder, piston, or ram, fuel tank, pump, injectors, and other pertinent parts. The ram of these hammers is raised by explosion of diesel fuel ignited in the cup or anvil of the hammer. Some types of diesel hammers are called double acting hammers. This type of hammer has the ram enclosed. As the ram travels upward, the piston compresses air in the bounce chamber-compressor tank. This compressed air adds to the acceleration of the ram during its downward stroke. It is necessary to use a "Bounce Pressure" gauge on this type of hammer to establish the usable energy for input into the FHWA-modified Gates dynamic pile formula for the nominal axial compressive resistance determination.

The single acting series of diesel hammers have a "rampiston" which can be partially seen during the upward stroke. If the manufacturer's rated energy is to be used in the FHWA-modified Gates dynamic pile formula then the inspector must determine that the ram is falling through a normal stroke. Failure to operate properly is usually the result of mechanical problems which the contractor must correct. In isolated instances, failure of the hammer to operate with a normal stroke may be caused by the elastic rebound of the pile and bearing material. If the ram is not falling through its usual stroke, the energy "E" used should be the energy which can be calculated from the weight of the ram times the actual stroke through which it falls. The height is determined from the observed exposed length of ram as the ram travels upward.

702.1.4.2 Pile Dynamic Formula

MoDOT may specify the use of the FHWA-modified Gates dynamic pile formula (see Sec 702.4.10) to calculate pile nominal axial compressive resistance. The Pile Driving Set Calculator is a spreadsheet that can be used to calculate the blowcount (N) in blows per inch of pile permanent set (BPI) to determine when to stop driving pile.

702.1.4.3 Pile Driving Specifics, Special Conditions and Inspection

Preparation for Pile Driving

  • A qualified inspector shall be assigned continuously on pile driving work to see that each pile is driven to the specified nominal axial compressive resistance and that all piles are properly located and driven.
  • The inspector must keep a detailed record of the data for each pile. The record should show for each pile, its position, tip and cut-off diameter (for timber), total length in place, length placed in leads, tip elevation, batter, and number of blows per inch (BPI) at the time driving is stopped.
  • The number of blows per inch is based on penetration for the last series of 10 to 20 blows per inch.
  • The inspector shall record all pertinent information regarding the hammer used so that a review and check of nominal axial compressive resistance may be made.
  • Any unusual occurrences or delay during driving shall be recorded.
  • When driving friction pile, the inspector shall make periodic resistance checks as the pile is being driven to know at any time the approximate nominal axial compressive resistance of the pile if problems should develop.

Lifting Holes

Contractors that elect to place lifting holes in piling in lieu of using a choker cable may be permitted to do so with the following provisions. The concern of burning lifting holes in piling is that undesirable capacity reductions may occur. Lifting holes would only be permissible provided they would not remain in the piling lengths used for the completed structure, i.e. lifting holes would need to be in an excess length of end piling which would either be cut off after driving, or in the case of splicing the holed end would be removed before splicing on the next section. Any added risk of buckling or damage to the piling that may result from a weakened cross section during driving is the contractor's responsibility.

There shall be no additional payment for the additional length of piling to compensate for removing the cut-off ends with the holes.

Pile Driving in Groups

It is good practice for piling in a group or cluster to be driven in sequence which proceeds from the center of the group each way to the outer rows of pile. This will usually avoid uplift and loss of resistance in previously driven pile. For a single row of piles, the sequence should follow end to end or middle to out but never end to middle from both ends.

The pile numbering on the As Built Pile Data plan sheet in the bridge plans is a random numbering scheme for the purposes of recording data and unrelated to pile driving sequencing. Just keep track of both numbering schemes to avoid confusion when recording during driving and recording final data on plan sheet.

Pile Driving to Soft and Hard Rock

In many cases piles are to be driven to rock or shale. The FHWA-modified Gates dynamic pile formula is applicable for soils, hard but penetrable material and soft rock. It is not applicable in hard rock at which point an inspector’s sense of anticipating elevation of hard rock coupled with the physical response of hammer and pile upon nearing and impacting hard rock is critical to properly seating HP piles on hard rock with limited to no pile damage. Since the nominal axial compressive resistance at the time of practical refusal is not an accurate resistance, the inspector should always be aware of the sounding data as the tip of the pile nears anticipated elevations of hard material. The pile should be seated on or into hard material with blows which will not damage the tip of the pile. Each bearing pile should be proofed for "practical refusal" unless it is clearly seated on solid rock.

The inspector will find other supplementary notes in the Foundation Data Table which should be taken into consideration for the proper and cautious driving of structural steel piles. It is especially important that steel HP piles which are to be seated on rock or shale be driven and proofed for "pile refusal" as specified in Sec 702.4.11. When the pile is well seated, the driving should cease. The inspector should record in the diary that the pile has been driven into shale or rock as the case may be. Either record penetration and bearing in the case of practical refusal or note "refusal on rock" in the case of absolute refusal on rock. Such notations will indicate full compliance with pile resistance requirements on the plans.

Piles to be driven shall be plainly marked at a distance from the tip equal to the distance from ground line to the elevation shown on the soundings for rock or shale. It is also good practice to mark the pile from the tip equal to the distance from the ground surface down to any layer of boulders, thin rock strata, or other hard or firm material which might cause unusual driving conditions and point resistance. The pile driving foreman or contractor's foreman shall be instructed on the significance of such marks and all personnel shall be instructed accordingly. This procedure will result in fewer damaged piles. The goal is to have no damaged piles.

Pile Splices

Splices may be required to extend structural steel or steel shell pile to reach adequate nominal axial compressive resistance. No direct payment will be made for splices that are within the plan pile length. Any splices outside of plan length required to achieve resistance will be paid for as an additional 8 feet of pile in place at the contract unit price per authorized splice. Field splices have a greater potential of failure during driving than the original furnished pile. Therefore it is preferable to have a minimum amount of field splicing. Sec 702.4.6 states, "Full length piles shall be driven wherever possible and practical." A full length pile should be used unless there is clearance, shipping, excessive cost, or other considerations which would make it impractical.

Structural Steel HP Pile:

Manufactured Pile Splices
MoDOT has received and approved one type of manufactured pile splicer for use with recommended guidelines. The AFB Champion H-Pile Splicer HP-30000 has been approved. The following are recommended guidelines that should be used beyond the manufacturer’s recommended assembly procedure for the use of the HP-30000 splicers:
1. It would be permissible for non-flexible bent locations only. This would include intermediate bents on pile footings and semi-deep abutments. This splicer system should not be used on flexible bents, such as pile cap intermediate bents, where the concrete beam is supported on a single row of exposed piling or on integral or non-integral end bents.
2. Full penetration groove welds connecting the pile flanges are required. The partial penetration groove welds as recommended by the manufacturer are not acceptable.
3. A 5/16" minimum fillet weld should be added at both ends of the splicer, welded to the pile webs. The length of this weld should be at least 1/2 the depth of the pile. This weld was not a recommendation of the manufacturer. This weld is for additional safety in the event that the splicer is damaged or torn from being snagged on rock material.

Cast-In-Place Concrete Piles (CIP):

For splice details, see:

Bridge Standard Drawings
Pile

Pile Inspection

The inspector must ensure that all piles have been properly inspected. Piles that are cast-in-place on the job shall be inspected using the same inspection procedures as for any other concrete item. Files should contain any applicable inspection reports on aggregate, cement and reinforcing steel. The concrete Plant Inspector's Report and compressive test reports will serve to document acceptability of piles. Steel shells for cast-in-place piles and structural steel piles are normally inspected by project forces. Inspection should include dimensions, wall thickness of shells, visual inspection of welds, closure plates, etc. The contractor is required to furnish certified mill test reports for the steel. Heat numbers of pile should be checked against heat numbers on the mill test reports. The resident engineer should report the results of inspection on a Fabrication Inspection Report, Form B-708R2, or an alternate format may be used. A spreadsheet version of the form is available to facilitate the automatic creation of an AASHTOWARE Project (AWP) record for use by the Construction and Materials Division. This information will be retained in the project file with mill test reports attached.

Pile Driving and Preboring

In some instances preboring is required as outlined in Sec 702.4.3. Preboring can be required on the bridge plans:

1. When there is more than five ft. of embankment that has been in place less than five years to avoid buildup of downdrag forces (called negative skin friction)
2. When hard material must be penetrated to meet minimum tip elevation requirements
3. When oversized holes in hard material or rock must be constructed to allow lateral pile movement

In any case, the requirement for preboring will be noted on the bridge plans for each pile with an elevation given for depth of preboring which is used to estimate and check proposed preboring quantities on the plans.

For prebored holes not in hard rock, holes shall be filled with sand or other approved materials either prior to or after pile placement. For prebored holes in hard rock, holes shall be filled with sand or other approved materials prior to pile placement. Filling the hole with sand first will condense sand and stabilize pile while driving on hard rock. The driving criteria for driving piling on hard rock shall be the same as given in Sec 702.4.11.

Where pre-boring is required the hole shall be of a diameter not less than that of the pile unless oversized as explained previously and shall be large enough to avoid damage to the pile in driving through the hole when in soft or hard material including rock.

Caution is warranted when driving piling in prebored holes in hard rock. Pile instability is increased because of initially loose sand condition. Absence of more stabilizing stiffer soils and hard material over rock that can act to reduce bending and buckling can cause more pile spring and bounce. Pile point damage is at increased levels of risk because proofing rock in excess of driving criteria given for driving piling on hard rock can be greater since there is only loose sand acting in friction along the sides of the pile which if compacted would normally tend to dissipate energy as the impact wave travels down the pile. This is why sand is placed in the hole prior to pile placement in order to increase the frictional condition while increasing buckling stability of the pile.

702.1.4.4 DFI Documents on Pile Driving and Hammers

Deep Foundations Institute (DFI) produced and published two critical documents in 1979 and then republished them in 1995 and 1997 related to pile hammers and pile driving. Copies of these documents were purchased from DFI and permission was granted by them for making these documents available on-line to MoDOT personnel only. The document links will not be available to external users outside MoDOT IS network environment.

These documents are provided for further guidance and understanding of pile driving and equipment. They do not reflect the policy of MoDOT, but can be used to support and reinforce decisions involving pile driving and equipment since the background and source of this information is time tested and produced by a reputable organization.

(1) Deep Foundations Institute (DFI), Inspector’s Manual for Driven Pile Foundations, 2nd Ed. 1997. Englewood Cliffs, New Jersey

Information published within this main document:

  • Provides Information on soil investigation, the various pile types, pile driving by impact methods, pile tests, pile dynamic testing and analysis, static load testing, pile hammers and pile driving machinery and ancillary equipment
  • Explains increases in driving resistance with depth in uniform soils
  • Explains driving resistance as a function of N-values
  • Explains changes in driving resistance as soil layers change
  • Explains pile markings, finer increments and how these are effectively used
  • Provides good description of scenarios when blowcounts are changing
  • Provides basic rules to be followed DURING driving and when approaching termination
  • Provides guidance on termination criteria
  • Provides explanation of pile dynamic testing
  • Provides explanation of static load testing (which we have been doing lately because of Missouri University of Science and Technology research project)
  • Written from the perspective of the pile inspector and presents advice as to the inspector's role and responsibilities in the pile installation and quality assurance processes
  • Provides invaluable training for inexperienced Inspectors and a useful reference guide for the experienced inspector or crew member.

(2) Deep Foundations Institute (DFI), A Pile Inspector’s Guide to Hammers, 2nd Ed. 1995. Springfield, New Jersey

Information published within this companion document:

  • Explains fundamentals of hammer efficiency and hammer measurement
  • Provides basic information about hammer types
  • Provides operational conformance checklists for inspectors for each hammer type
  • Provides possible helpful suggestions for troubleshooting and what an inspector can offer to the pile crew in assisting them.

702.1.5 Pile Driving Documentation

The inspector should record in detail all important facts regarding driving of each pile. The field book notes should be organized in a sequence similar to that shown in the Pile Driving Worksheet.

The sample form in the Pile Driving Worksheet illustrates a typical page of completed pile driving data for cast-in-place concrete pile. Data in a similar form will be filled out when driving structural steel pile.

Figure 702 is an illustration of field book data for driving structural steel pile. The inspector records the actual length used and notes the number of pieces incorporated in the length. When structural steel pile is driven, there is often a piece left over from the in-place pile which becomes excess or left-over pile. The contractor may wish to use such a piece on another state highway project. If transfer to another project is desired, extra copies of the certified mill test reports should be made which can be used to have the excess pile reinspected on a future project.

Probe Pile

If probe pile is a contract pay item, it must be driven to specified minimum tip elevation regardless of the nominal axial compressive resistance achieved. After this elevation is reached, driving must continue until one of the following three conditions has been met:

l. The pile is driven to full length
2. The pile is driven to refusal
3. The pile is driven to a capacity 50 percent greater than plan minimum nominal axial compressive resistance.

These conditions are specified in Sec 702.4.1. It is important that a complete driving log be developed. The pile should be marked off in foot increments. The driving record should then show the number of blows for each foot. Some arrangement is necessary to check number of blows per foot without stopping the driving. If there is a sudden sharp change in the number of blows for a given penetration, it may be necessary to check resistance for intermediate increments to develop an accurate graph. The results of specified probe pile driving are to be reported on Probe Pile Data form. Contact the Construction and Materials Division for assistance in reporting probe pile data.