any readings indicate that the new embankment has settlement greater than 1/4 in., the monitoring period will be extended until the settlement requirements are met. 70 Settlement stakes will be used to measure the vertical movement, in conjunction with settlement plates if specified. Settlement stakes and settlement plates will be monitored at the same time and interval. M easurements will be made to the nearest 1/4 in. Within one day of the readings, settlement data will be sent electronically to the Department’s Geotechnical Engineering Division and will be subject to approval. Lateral stakes will be used to monitor horizontal movement of the ground or new fill. If lateral movement is noticed during the construction of the fill, the work will be suspended and the Department’s Geotechnical Engineering Division will be contacted. Measurements will be made to the nearest 1/4 in. 80
Settlement plates, extension pipes, cover pipes, and stakes shall be protected during construction operations and during the monitoring period. (c) Protection and Maintenance The settlement stake and settlement plate shall remain in a vertical position. The Contractor shall ensure that settlement plates and settlement stakes are not damaged or displaced. Settlement stakes and settlement plates deviating from a vertical position, becoming uncoupled, or broken shall be repaired or replaced by the Contractor, as directed by the Engineer. 90
The Contractor will not be held responsible for repair or replacement of any settlement plate assembly which is damaged as a result of instability of the embankment caused by factors beyond the control of the Contractor, as determined by the Engineer. 204.04 Standpipe Piezometers The standpipe piezometers shall be installed by a geotechnical consultant on the Department’s Qualified Geotechnical Consultant’s List prior to placing the first lift of embankment. Piezometer consists of a 1/2 in. leak proof, flush-coupled Schedule 80 100 PVC pipe or ABS standpipe extending to the surface of the embankment with an attached polyethylene tip in accordance with AASHTO T 252.
A separate water-monitoring borehole shall be installed outside the influence of the fill as shown on the plans. This shall be a minimum 2 in. diameter borehole, cased with slotted pipes, drilled to a recommended depth and location or as directed by the Engineer, to establish groundwater elevation prior to piezometer installation.
The installation of the standpipe pi ezometer shall precede placement of any 110 embankment by at least two weeks to allow time for testing of the installation. The piezometer shall be maintained and protected during the embankment construction. 204.04 192 The hollow stem auger shall be advanced to an approximate depth of 6 in. below the recommended piezometer tip elevation. Augers shall be cleaned and washed inside for their full length, until the wash water runs clear. The auger shall be withdrawn 6 in. by means of jacking or other steady pull operations. The hole shall be filled to the bottom with saturated Ottawa sand and tamped with an annular tamping hammer. The elevation shall be measured and provided to the Engineer. 120
The tip shall be attached to the standpipe and tested for free flow of water. The bottom end of the tip shall be plugged and soaked in water if a porous stone tip is used. The tip and standpipe shall be filled with clean water. The tip shall be lowered into the auger until it rests on the top of the sand pl aced and the elevation of the tip should be documented. Excess head shall be maintained in the standpipe during lowering to ensure that a small amount of water flows out of the tip. The auger shall then be pulled or jacked a distance equal to the length of the tip in increments of 6 in. The hole shall be filled with water saturated Ottawa sand at each 130 increment. This layer of sand shall not be tamped in order to avoid damage to the tip. The auger shall be raised 12 in. and the hole filled with saturated Ottawa sand in 6 in. increments until the backfilling reaches a minimum of 6 in. below the elevation of the strata change or as directed by the Engineer. In locations where there is no strata change, the Ottawa sand shall be placed a mini mum of 12 in. above the top of the tip.
The augers shall then be raised and the hole sealed with bentonite chips in accordance with AASHTO T 252 which shall be placed in 6 in. lifts. The top of the seal shall be a minimum of 6 in. above the strata break. A weighted line shall be used 140 to ensure the bentonite seal is in place. The remainder of the hole shall then be backfilled with bentonite-cement grout as the augers are withdrawn. The riser pipe shall be kept in tension and shall be centered in the auger while backfilling. Depths for various stages shall be recorded on the Engineer’s logs. If the piezometer location is not in an ar ea of proposed fill, an approximately 3 ft long protective metal cover shall be installed at the top with approximately 2 ft below the surface and 12 in. above the surface. A 12 in. diameter by 6 in. thick circular pad of coarse aggregate shall be filled around th e cover. A lockable cap shall be securely attached onto the pr otective metal cover. 150 If the piezometer location is in an area of proposed fill, a PVC casing shall be used around the piezometer standpipe in order to protect the pipes during embankment construction. B borrow shall be placed and compacted around the casing without disturbing the casing. The casing and standpipe shall be extended as the fill is placed by adding extra lengths not to exceed 5 ft. The top of the st andpipe shall be at least 12 in. above the 204.04 193 grade of the new fill. Each time the casing and standpipe are extended, the casing shall be filled with structure backfill. The last extension of pipe shall be of such length that 160 it extends 12 in. above grade. It shall be filled with structure backfill to within 9 in. of the top of the casing. A 12 in. diameter by 6 in. thick circular pad of coarse aggregate shall be filled around the pipes. A lockable cap shall be securely attached onto the protective cover. When the standpipe is completed it shall be checked for obstructions by dropping a weighted line through the pipe. The sta ndpipe shall then be filled with water and periodic readings made of the water level until the groundwater level is stabilized. Hydrostatic time lag required for equalization will be provided by the Geotechnical report. If required, the standpipe shall be flushed and retested at the direction of the 170 Engineer. Groundwater readings shall be provided to the Engineer. Standpipe piezometers, and cover pipes shall be protected during construction operations and during the monitoring of the fill. In the event of damage, fill construction shall be suspended in this area until the piezometer is restored. (b) Readings and Maintenance of Piezometer The Engineer will conduct and record all observations and measurements required to determine natural groundwater elevations and pore pressures induced by embankment construction. Monitoring intervals will be once every day for the first 180 seven days, once every other day for the next eight, and then, once every three days through the end of construction of the fill. The elevation of the natural groundwater existing at the time of installation, prior to placement of any fill, will be used as a reference to determine baseline pore pressures. Groundwater and pore pressure test results will be made available to the Contractor. The pore pressure measurement in conjunction with the settlement data will be sent electronically to the Department’s Geotechnical Engineering Division within one day of the readings, and will be subject to approval. If it is determined that pore-water pressures have not sufficiently dissipated , fill placement shall be suspended, and the 190 monitoring period extended as directed. If monitoring is to be continued after pa ving in a traffic accessible area, then the pipe shall be cut off 6 in. below the finished grade and a handhole in accordance with 807.09, shall be installed for monitoring access. When the evaluation is completed, the water monitoring borehole and piezometers shall be backfilled with bentonite-cement grout. 204.05 Method of Measurement Settlement plates, settlement stakes, late ral stakes, standpipe piezometers, and 200 water monitoring boreholes will be measured by the number of units installed.
204.06Basis of Payment
Settlement plates, settlement stakes, late ral stakes, standpipe piezometers, and 204.06 194 water monitoring boreholes will be paid for at the contract unit price per each.
Payment will be made under: Pay Item Pay Unit Symbol 210 Settlement Plate ......................................................................... EACH Stake, Lateral ............................................................................. EACH Stake, Settlement ....................................................................... EACH Standpipe Piezometer ................................................................ EACH Water Monitoring Borehole....................................................... EACH The cost of furnishing, installing, and maintaining settlement plates, extension pipes, cover pipes, B borrow, structure backfill, coarse aggregate and all necessary incidentals shall be included in the cost of settlement plates. 220 The cost of backfilling water monitoring boreholes will be included in the cost of water monitoring boreholes. The cost of handholes, protective covers, bentonite chips, bentonite-cement grout, Ottawa sand, tips, casing, drilling, tubing or PVC pipe, backfilling and measurements will be included in the cost of standpipe piezometers. No additional compensation will be made for any costs incurred related to the repair of settlement plates, pipes, settleme nt stakes, lateral stakes or standpipe piezometers as the result of damage by the Contractor. 230