Category:204 Embankment Monitoring
204.1 Construction Inspection Guidance For Sec 204
Occasionally, it is desirable to hasten the natural settlement and associated consolidation that occurs in any embankment over a period of time. A surcharge (adding soil above the designed profile elevation) is added which temporarily increases the weight of a fill. The contract usually establishes the height of extra material to be added and when the surcharge may be removed. Care must be taken to prevent embankment and surcharges from being built so rapidly that the foundation soil fails in shear, allowing the whole mass to slide. The contract usually specifies a rate of fill placement in surcharged areas if this item is critical.
Associated with the construction of surcharged fills is installation of embankment control stakes, settlement gauges and pore pressure measurement devices. Embankment control stakes are placed along the toe of the embankment to determine whether the embankment is moving laterally. Movement will be apparent by the fact that the stakes have either moved laterally or have tilted.
Settlement Gauges (Sec 204.10)
Description (Sec 204.10.1)
Settlement gauges are installed to permit determination of the rate at which the natural ground is subsiding under embankment. The rate of settlement usually controls the time when the surcharge may be removed. The major problem associated with settlement gauges is binding of the rod used for measurement when the fill moves laterally and warps the sleeve pipe surrounding the gauge.
Material (Sec 204.10.2)
Construction Requirements (Sec 204.10.3)
Basis of Payment (Sec 204.10.4)
Surcharge material is to be cross-sectioned before removal and payment will be made as provided by contract for the applicable item. Gauges that become inoperative are not considered satisfactory for payment purposes. Standard Specifications requires the contractor to repair or replace damaged gauges at the contractor expense.
Pore Pressure Measurement Devices (Sec 204.20)
Description (Sec 204.20.1)
Pore pressure measurement devices are used to determine natural ground water pressures and pore water pressures induced by embankment construction. The rate of placing embankment is frequently controlled by the increase in pore pressure measurements.
Equipment (Sec 204.20.2)
Construction Requirements (Sec 204.20.3)
Pore Pressure Measurements and Records (Sec 204.20.4)
Settlement Records (Sec 204.20.5)
Basis of Payment (Sec 204.20.6)