Method Statement For Plate Load Test (Final) - Ns37 [PDF]

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FOUR LANNING OF NH 1A JALANDHAR-PATHANKOT SECTION CONSTRUCTION PACKAGE: NS-37(PB)

1.0 PURPOSE The purpose of this document is to detail the procedures for conducting plate load test for estimating the bearing capacity of shallow foundation on soil and for obtaining the soil modulus for the purpose of estimating the settlement of foundations on soil. The documentation will apply to all engineer, workmen, quality control personnel and inspectors connected with this job. 2.0 SCOPE This work will involve selection of location of test, arrangement and conducting plate load test applying vertical load, observation and recording settlement data / results obtained during load test, submission all data to the Engineer or his representative for his further instruction. 3.0 REFERENCES i. Specifications for Road and Bridge works, Ministry of Road Transport & Highways (MORTH) – 4th. Revision. ii.Technical Specifications: Volume – II of Contract Document No. NS-37(PB) iii.Drawings. DRG. No. Sowil / NH – 1A / JP / LT – 1 / 37 iv. Method of load test on soils ( Second Revision) – IS1888 - 1982 4.0 PROCEDURE The procedure described below will apply for arrangement and conducting plate load test applying vertical load unless and otherwise specifically mentioned. 4.1 Selection of Location of Plate Load Test : Plate load test shall be carried out for such structures as mentioned in Clause 2104.3 of Technical Specification, Vol – II of the Contract Document and drg. No. Sowil / NH –1A / JP / LT – 1 / 37 at location(s) instructed by the Engineer or his representative. The test shall be at a proposed foundation location or within a distance of 10m from the site of the foundation as per instruction of the Engineer or his representative depending upon the condition of site. Number of tests to be conducted shall be as per drg. No. Sowil / NH –1A / JP / LT – 1 / 37 of the Contact Document or as instructed by the Engineer or his representative. 4.2 Selection of level of Plate Load Test The plate load tests shall be carried out, in general, at proposed founding level or as decided by the Engineer or his representative. In case the water table is within the depth equal to the width or diameter of the plate, the test shall be conducted at water table level. In case water table is higher than the test level, it shall be lowered to the test level by pumping through a sump, at the corner of the test pit. For cohesionless soils like silt, sand, sand mixed with boulders which cannot be drained by pumping from the pump, the test level shall be water table level.

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FOUR LANNING OF NH 1A JALANDHAR-PATHANKOT SECTION CONSTRUCTION PACKAGE: NS-37(PB) 4.3 Excavation Of Test Pit Rough excavation of pit for plate load test will be carried out with mechanical means followed by manual dressing / trimming of side to a level 300mm above the test level. Size of the pit at test level will be about 4m x 4ml. Side of the pit shall be provided with slope against slippage. Suitable benches shall also be made to keep the sides stable and for erection of loading platform, if required. All boulders and loose materials on slopes shall be removed. Final excavation of 300mm will taken up after erection of the kentledge / reaction device. In case during the excavation water table is encountered, the matter is to be reported to the Engineer or his representative for his further instruction. Test pit shall be protected from rain and sun during excavation and testing. An easy access is to be provided to the bottom of the pit from the side. 4.4 Inspection and logging of excavated pit Immediately after mechanical excavation is completed and side dressing is over, the freshly cut soil surfaces of the pit are to be examined and the pit shall be logged at four corners. Record of such examination and logging are to be maintained jointly with the Engineer or his representative. A copy the record is to be submitted to the Engineer or his representative. A pit is to be dug manually, maximum upto 500mm below the test level, to collect soil sample jointly with the Engineer or his representative for determination of MDD and OMC at site laboratory. 4.5 Erection of kentledge / Reaction Load Platform Load will be applied taking reaction from a kentledge / reaction load platform placed on top of the test pit. Kentledge load shall be such so that maximum required load can be applied during testing. Supporting frame shall be made with steel structurals. 4.6 Placement of Test Plate and other accessories and determination of Insitu Density of soil at Test Level. After erection of kentledge is completed, final 300mm of excavation is to be done manually and the excavated material will be taken out. The excavated surface at the test level shall be undisturbed, plane and free from any crumbs of loose debris. After clearing the pit, in-situ density test is to be carried out at the test level by sand replacement method jointly based on MDD and OMC value obtained at site laboratory with the Engineer or his representative and recorded. Size of mild steel plate shall be 600mm x 600mm x 25mm ( thk). The test plate is to be placed over a thin layer ( maximum 5mm thk) of clean sand or cement – sand mortar ( 1:3) as bedding material. No. of concentrically placed smaller plates of 450mm x 450mm, 300mm x 300mm, each of thickness 25mm shall be placed over the test plate to prevent upward deflection of the free edges of the test plate. Centre of test plate together with the plate assembly on top of it shall coincide with the centre of reaction girder / beam of the kentledge / reaction load platform. The hydraulic jack shall be placed centrally over the top most plate. In case it is required, a grillage / loading column may be placed to adjust the gap between the top of the jack and bottom of the reaction beam for application of load. Two supports of reference beam or datum bar shall be placed over firm ground at a distance not less than 1.5m from the centre of the plate, fixed with four dial gauges placed diametrically opposite corners of the test plate.

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FOUR LANNING OF NH 1A JALANDHAR-PATHANKOT SECTION CONSTRUCTION PACKAGE: NS-37(PB) A sump is to be kept at a corner inside the pit to pump out water, in case required. The pit shall remain free of water during testing.

4.7

Application of load and recording Test Data Calibration certificate of pressure gauge and dial gauges are to be submitted to the Engineer or his representative prior to start of testing. The load is to be applied vertically without impact, fluctuation or eccentricity. A seating pressure of 70 gm. / sqcm or as instructed by the Engineer or his representative shall be applied and removed in single stage prior to start of load test. The seating load is to be maintained till the rate of settlement is reduced to 0.02 mm / minute. Maximum test load to be computed considering 2.5 times the design bearing pressure and applied in ten cumulative equal increments. Settlement shall be observed and recorded jointly with the Engineer or his representative for each increment of load after an interval of 1. 2,4, 6, 9,16, 25mins and there after at hourly intervals to nearest 0.02mm. The next increment of load shall be applied when the settlement reading is reduced to a value of 0.02mm / min. or one hour which ever is more. The next increment of load shall then be applied and settlement observation recorded. The test shall be continued till a settlement of 50mm is obtained or shear failure of soil occurs or the applied test load has reached to two and half times the design bearing pressure, which ever is earlier. Unloading shall be done in five cumulative equal decrements with time interval between each stage of decrement shall not less than 15 minutes. Rebound observations will be recorded jointly with the Engineer or his representative while releasing the load at an interval of 1.2.5.9 and 15 minutes. Final rebound will be observed and recorded one hour after withdrawl of all load on the test plate. 4.8 Preparation and Submission of Records Based on the observation and recorded data the Contractor shall plot (i) Load settlement curves in arithmetic as well as in logarithmic scales (ii) time settlement curve for each stage of loading. The contractor shall submit to the Engineer or his representative details of loading and pressure / load applied, load settlement observation and recorded data, load settlement and time settlement curves for his onward instruction. 4.9 Excavation of Pit below Test Level. After completion of plate load test, a pit of 3 m deep below the test level or as decided by the Engineer or his representative considering feasibility at site, is to be excavated to observe the strata beneath the test level. A record of such observation jointly made with the Engineer or his representative is to be prepared and submitted 5.0 Plants and Equipment The following plants and equipment will be deployed for conducting the test , in general – i) Excavator – 1 No. ii) Kentledge Platform – 1 set iii) Load test equipment Comprising of test plate, Datum bars, hydraulic jack DOC NO: - NS37-MS- STRUC- PLT-REV-0 PAGE 3

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FOUR LANNING OF NH 1A JALANDHAR-PATHANKOT SECTION CONSTRUCTION PACKAGE: NS-37(PB) with pump, pressure gauge, Dial gauges, magnetic bases etc. 1 set iv) v) vi)

Water pump complete with suction and deliverySoil test equipment Other tools and tackles -

1 No. 1 No. As required.

6.0 Safety 1. Workmen, Engineers, supervisors, inspectors shall use safety attires. 2. Proper arrangements shall be made for illumination of test pit and its surroundings. 3. The area of testing shall be barricaded. 4. The pumping unit of the hydraulic unit shall be kept out side the test pit away from the kentledge. 5. Persons required for taking the reading shall only be inside the test pit.

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