User:Hoskir/Revision Request 4256 - Revision history

Hoskir: /* 321.2.3.3 General Procedures */

2026-08-21T18:17:41Z

321.2.3.3 General Procedures

← Older revision		Revision as of 13:17, 21 August 2026
Line 258:		Line 258:

	7. Air Photos		7. Air Photos

	~~===321.2.3.3 General Procedures ===~~

	The first step after receipt of a request from the Bridge Unit or district is a file search for soil survey reports, preliminary bridge reports, and foundation reports for adjacent structures. A packet of information, which includes plans, correspondence, and prior reports is assembled for field use. Next, the district is consulted for advice as to field conditions, problems with utilities, crops, landowners, etc. If site access conditions are especially bad, someone from the [http://sharepoint/systemdelivery/CM/geotechnical/default.aspx Geotechnical Section] may visit the site to determine what equipment may be needed and how the site can be reached. As noted previously, either the Bridge Unit or the district's boring plan may be modified as appropriate given site conditions and constraints. Some of the considerations here include:

	:'''1. General knowledge of conditions in the physiographic or geologic area where the work is to be done.''' This strongly influences the kind of investigation which should be performed and how detailed it should be. For example, in the Springfield area, residual clay over heavily pinnacled rock is likely and the most important thing is to map the rock surface irregularities with a lot of auger borings to rock so that point bearing pile lengths can be determined. In the bootheel area, auger borings are virtually worthless and standard penetration test borings for design of friction piles are most important.

	:'''2. Site access conditions are a very practical consideration.''' It may just not be feasible to drill a hole in the middle of an urban interstate highway and it may be extremely difficult and/or expensive to drill one in the middle of a river. That is where judgments must be made about how necessary that particular boring is: can conditions be reasonably extrapolated from offset borings, would geophysical methods work as well, etc.? In many cases, the borings can be omitted with little risk. In other situations, considerable expense and trouble may be justified to get on location. This may involve a different type of equipment, hiring a bulldozer, mobilizing the portable barge, or temporarily blocking a lane of roadway. The most extreme access problems involve major river or lake crossings where barges, tugs, and support services must be provided by contract.

	:'''3. The third consideration involves foundation conditions actually encountered as the investigation progresses.''' This is a principal reason why all MoDOT foundation investigations are supervised in the field by trained personnel. If conditions encountered are different than anticipated, it is expected that the scope of the investigation will be adjusted as necessary to fit actual conditions.

	:'''4. As previously noted, the Geotechnical Section rarely makes recommendations for specific foundation types.''' The basic aim is to furnish the Bridge Unit with the information needed to develop designs for foundation types practical for a particular site. Several rules of thumb are helpful in deciding what is practical. For example:

	~~::'''a. Spread footings'''~~

	::Spread footings for bridges will not be considered unless foundation material has an unconfined compressive strength of 3 tsf or more, and such material is within a fairly shallow depth. If firm material is 10 feet or more below final grade line, then piles will be used.

	~~::'''b. Deep Foundations '''~~

	::MoDOT guidelines used to estimate how far to carry standard penetration tests for design of friction piles are 30 continuous feet of bearing strata with an N60 value of 20 or greater. It is normal practice to drill half again as deep, or at least 100 ft. in any case, to check depth to rock for a point-bearing option. Point bearing is usually a feasible option almost everywhere in the state except in the southeast lowlands or "bootheel" area where sands extend to depths of several thousand feet. Even here, however, a careful check must be made for the possible presence of soft clay layers within and just below the range of probable friction pile penetration.

	~~::'''c. Culverts with Floor Slab Omitted '''~~

	::Large box culverts may be built more economically if a floor slab can be omitted. The Bridge Unit feels this is generally feasible if rock is within five feet of flowline. So, where rock may be shallow, an attempt is made to drill auger holes every 25 ft. or so along each proposed wall. An attempt is made to judge the durability of the rock based on inspection of exposures and cores and knowledge of past performance of particular formations. The rock should have an RQD equal to or greater than 75 and should not be thin bedded. If rock is deeper, only a few auger borings to verify this fact may be sufficient.

	~~::'''d. Culverts with Compressible Foundations '''~~

	::Culverts, if built over compressible foundations, may require special investigations based on undisturbed sampling to determine need for camber to compensate for settlement and to assess the danger of joints opening due to spreading caused by settlement. In some areas of the state where this is a particular problem, structural collars are sometimes recommended around joints to control spreading and faulting and piping of silty soils into opened joints.

	~~::'''e. Retaining Structures '''~~

	::For retaining structures, information is obtained for determination of allowable footing bearing pressures and angles of internal friction of the materials to be retained and the foundation material. The latter is done by correlation to Plasticity Index (PI) for walls of low height (using the average correlation less one standard deviation), Appendix F, and by drained shear testing for higher and more critical structures. In some cases, it may be necessary to obtain undisturbed samples for testing in order to evaluate overall stability of the slope of which the wall will be a component. By agreement with the Bridge Unit, evaluation of global or overall stability is a Geotechnical Section responsibility. If inadequate global stability is likely, possible solutions are evaluated - such as lowering the base of the wall, increasing the width to height ratio and excavation and replacement with rock fill, etc.

	~~::'''f. Spill and Channel Slopes '''~~

	::The Geotechnical Section attempts to furnish overall guidance on prudent slope selection. This was done first by development of criteria, based on soil type and geologic origin, which is used by the district geologist in making project slope recommendations. Secondly, a review is made, often by specific request of the Bridge Unit, of the adequacy of embankment stability in the vicinity of the bridge ends, particularly at stream crossings. Geotechnical recommendations may affect bridge length, the fill end slopes, and erosion control measures for the channel banks. Often, for example, evidence will be found of channel bank failures which reflect a need for bank stabilization or bridge lengthening.

	~~::'''g. Special Investigations '''~~

	::These investigations were discussed in Section I where it was noted that, while normally initiated by the district as part of the soil survey, a problem may not be identified until final bridge soundings are being done. Undisturbed foundation sampling is done or supervised by a geologist, engineer, or senior technician. Large diameter samples are strongly preferred, often of 5 in. diameter, although 3 in. diameter samples are also commonly taken. In very soft soils, piston samplers are used in lieu of the normal Shelby tubes. Continuous undisturbed sampling is preferred, with frequent use of a 5 in. sampler, then a 3 in. sampler, followed by pushing a split spoon for inspection before cleaning the hole and restarting the cycle. MoDOT practice differs from that of many agencies in that soil samples are routinely extruded in the field. This permits thorough inspection and logging, obtaining field moisture and Atterberg Limits Classification samples, and preliminary field testing with the Torvane and Pocket Penetrometer. Most important, it permits the technical supervisor to develop a good feel for the problem as the investigation progresses. Samples are selected and designated at this time for certain types of testing, wrapped in foil, and sealed in wax in cartons for transport back to the lab. [[image:321.2.3.3.jpg\|right\|275px\|thumb\|<center>'''Direct Shear Testing'''</center>]]For a typical problem involving an embankment settlement and stability problem, the lab testing program will include moisture contents, Atterberg limits, consolidation tests, unconfined compression, and drained, direct shear tests, all supplemented by Torvane and Pocket Penetrometer tests. Stability analyses are performed using a computer program, either circle analysis (Bishop), block and wedge (Spenser), or both as may be most appropriate for particular circumstances. Total strengths are used to assess the initial or rapid construction case. Effective stress analyses are used to assess fully consolidated conditions as well as intermediate degrees of consolidation. This data can be interpreted to assess the need for controls on rate of construction.

	::Amount of settlement estimates have been found to be fairly accurate. Actual rates of settlement are usually, but not always faster, than predicted. If a predicted time of settlement appears critical, office calculations are checked by doing field permeability tests and back figuring coefficients of consolidation. Usually, field perms will indicate much faster drainage, but sometimes agree very well with predictions based on laboratory tests. Before using vertical sand drains or any very expensive solution, field permeability testing should be done.

	===321.3.3.4 Division of Responsibility ===		===321.3.3.4 Division of Responsibility ===

Hoskir: /* 321.2.2 Technical Guidelines for Geotechnical Investigations */

2026-08-21T18:16:54Z

321.2.2 Technical Guidelines for Geotechnical Investigations

← Older revision		Revision as of 13:16, 21 August 2026
Line 166:		Line 166:
	A gradation sample, providing D50 and D90, of stream bank surficial materials is required for Bridge Divisions scour analysis. Check the PGR first, as the District Geologist may have already collected the sample.		A gradation sample, providing D50 and D90, of stream bank surficial materials is required for Bridge Divisions scour analysis. Check the PGR first, as the District Geologist may have already collected the sample.

	Bridges located in seismic zones may require earthquake sampling, the Request for Final Soundings for Structures Form and Bridge Seismic Design Flowchart (EPG 751.9) should be reviewed to verify need for additional sampling requirements (see Earthquake Sampling guidance, below).		Bridges located in seismic zones may require earthquake sampling, the [https://epg.modot.org/forms/general_files/BR/Request_for_Final_Soundings_for_Structures_Form.xlsx Request for Final Soundings for Structures Form] and Bridge Seismic Design Flowchart ([[751.9_Bridge_Seismic_Design\|EPG 751.9]]) should be reviewed to verify need for additional sampling requirements (see Earthquake Sampling guidance, below).


Line 196:		Line 196:
	The recommendations made as a result of these investigations may influence structures in various ways; bridge length may be affected, end fill slopes and culvert camber, etc. The most common effect is on construction sequence and rate of construction. Piles should not be driven in an embankment until it has stopped settling and until excess foundation pore pressures have dissipated.		The recommendations made as a result of these investigations may influence structures in various ways; bridge length may be affected, end fill slopes and culvert camber, etc. The most common effect is on construction sequence and rate of construction. Piles should not be driven in an embankment until it has stopped settling and until excess foundation pore pressures have dissipated.

	For embankments, i.e., roadway items, very specific recommendations are made as to remedial courses of action rather than saying here is the problem and leaving it to the designer to figure out a solution. However, more than one solution may be technically feasible and it should be realized that other considerations, such as economics, may dictate which solution is actually chosen. Face-to-face meetings with the concerned designers before a report is issued are important to permit mutual exploration of the problem and the ramifications of possible solutions.		For embankments, i.e., roadway items, very specific recommendations are made as to remedial courses of action rather than saying here is the problem and leaving it to the designer to figure out a solution. However, more than one solution may be technically feasible and it should be realized that other considerations, such as economics, may dictate which solution is actually chosen. Face-to-face meetings with the concerned designers before a report is issued are important to permit mutual exploration of the problem and the ramifications of possible solutions.

	==321.2.2 Policy Sources==		==321.2.2 Policy Sources==

Hoskir at 18:12, 21 August 2026

2026-08-21T18:12:02Z

Show changes

Hoskir at 17:16, 21 August 2026

2026-08-21T17:16:11Z

Show changes

Hoskir: Created page with "

321 Geotechnical Engineering
{| style="padding: 10px; margin-left:15px; margin-top: 5px; border:1px solid #a9a9a9; background:#f8f9fa" width="650px" align="right" |- | style="text-align:center;" | '''Reference Documents''' |- |..."

2026-08-21T17:10:18Z

Created page with "<div style="float: right; width: 660px;"> <div style="float: right; margin: 5px; margin-bottom: 10px; padding: 10px; border: 1px solid black; border-radius:5px; box-shadow:5px 5px 5px #888888"> <categorytree mode=all>321 Geotechnical Engineering</categorytree></div> {| style="padding: 10px; margin-left:15px; margin-top: 5px; border:1px solid #a9a9a9; background:#f8f9fa" width="650px" align="right" |- | style="text-align:center;" | '''<u>Reference Documents</u>''' |- |..."

New page

<div style="float: right; width: 660px;">
<div style="float: right; margin: 5px; margin-bottom: 10px; padding: 10px; border: 1px solid black; border-radius:5px; box-shadow:5px 5px 5px #888888">
<categorytree mode=all>321 Geotechnical Engineering</categorytree></div>

{| style="padding: 10px; margin-left:15px; margin-top: 5px; border:1px solid #a9a9a9; background:#f8f9fa" width="650px" align="right"
|-
| style="text-align:center;" | '''<u>Reference Documents</u>'''
|-
| ● [https://epg.modot.org/documents/321_Geophysical_Methods_FHWA_1998.pdf Geophysical Methods FHWA 1998]
|-
| ● [https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16072.pdf Geotechnical Engineering Circular No. 5 - Geotechnical Site Characterization, FHWA 2016]
|-
| ● [https://epg.modot.org/documents/321_Subsurface_Inv_Manual_FHWA.pdf Subsurface Investigation Manual FHWA 1997]
|-
| ● [https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi06088.pdf Soils and Foundations Reference Manual - Volume I, FHWA 2006]
|-
| ● [https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi06089.pdf Soils and Foundations Reference Manual - Volume II, FHWA 2006]
|}

{| align="center"
|-
|colspan="2"|[[Image:321 Drill in Creek.JPG | 550px]]
|-
|[[Image:321 Mine Map.JPG | 275px]]||[[Image:321 Driller.JPG | 275px]]
|-
|colspan="2"|[[Image:321 Slide.jpg | 550px]]
|}
</div>

The Geotechnical Section of MoDOT provides geotechnical laboratory and field testing as well as subsurface drilling. This section obtains and interprets the subsurface information needed to design highways and bridges. Soils and Geology personnel also investigate various geotechnical matters including foundation stability and settlement of embankments, slide corrections, subgrade and base stabilization, bridge and wall foundations, sinks and mine subsidence, and the use of new technology and products. The Geotechnical Section serves as a contact regarding geotechnical problems, new products, specifications, training programs and implementation of new products and procedures. This section also participates in proficiency sample programs and inspections by the AASHTO re:source.

Geotechnical functions in MoDOT are performed by personnel assigned to the Construction & Materials Division, both in the District and at Central Office in Jefferson City. Each of the Districts should have a District Geologist or Geotechnical Specialist who typically reports to the Assistant District Construction & Materials Engineer. Within Central Office, these functions are administered through the Geotechnical Section.

The Geotechnical Section has a specialized soil laboratory with technicians and equipment for performing consolidation tests, direct shear tests, and other specialized soil tests. Professional level employees with academic backgrounds in Geology and Civil or Geological Engineering concentrate on one or more specialties. The core drill section assigns equipment and personnel statewide as needed by either District or Central Office staff. The Geotechnical section completes all final foundation investigations for structures prepared by the Bridge Division as well as settlement and stability investigations as necessary. Other duties include slide investigations, work on subgrade and base stabilization, geophysical explorations, research activities and any other geotechnical problems as they arise.

The core drill section employs its own staff of field drilling personnel and drilling support equipment. Drilling equipment includes mobile power augers with pavement cores, CME 45 truck mounted rig, track mounted Acker Renegade, track mounted Acker XLS, and a track mounted GeoProbe 3135T SPT/CPT Rig.

This Geotechnical section typically provides three types of reports, a Preliminary Geotechnical Report (PGR), a Final Foundation Investigation Report (FFIR) and a Special Investigation Report.

The PGR touches on foundations by pointing out possible foundation problems. It also contains basic slope recommendations which affect bridge length, a preliminary bridge foundation boring, soil types and properties for pavement design, depths to rock and type of rock for determining cut quantities and cut slope recommendations for soil and rock.

The FFIR for structures starts with a formal request from either the Bridge Division or District following procedures in [[751.1_Preliminary_Design#751.1.2.19_Soundings_(Borings)|EPG 751.1.2.19]]. The Bridge Division or District will provide a preliminary layout and a suggested boring plan. This boring plan should follow [[321.2_Geotechnical_Guidelines#321.2.2 Technical Guidelines for Geotechnical Investigations|EPG 321.2.2]]. The suggested boring plan is only a guide which will be modified as deemed necessary in the field by the Geotechnical Section. The basic aim is to furnish the Bridge Division or District with the information needed to develop designs for foundation types practical for a particular site. The Geotechnical Section may make recommendations for specific foundation types if geologic conditions necessitate a change. Rules of thumb as to what is practical have been developed jointly by the Geotechnical Section and the Bridge Division.

Contact Information:
: MoDOT Construction and Materials Division
: 1617 Missouri Blvd
: Jefferson City, MO 65109
: E-mail: Lydia.Brownell@modot.mo.gov
::: Zachary.Troesser@modot.mo.gov

User:Hoskir/Revision Request 4256 - Revision history

Hoskir: /* 321.2.3.3 General Procedures */

Hoskir: /* 321.2.2 Technical Guidelines for Geotechnical Investigations */

Hoskir at 18:12, 21 August 2026

Hoskir at 17:16, 21 August 2026

Hoskir: Created page with " 321 Geotechnical Engineering {| style="padding: 10px; margin-left:15px; margin-top: 5px; border:1px solid #a9a9a9; background:#f8f9fa" width="650px" align="right" |- | style="text-align:center;" | '''Reference Documents''' |- |..."

Hoskir: Created page with "

321 Geotechnical Engineering
{| style="padding: 10px; margin-left:15px; margin-top: 5px; border:1px solid #a9a9a9; background:#f8f9fa" width="650px" align="right" |- | style="text-align:center;" | '''Reference Documents''' |- |..."