Arun Soil Lab Pvt.Ltd.
Geotech and Material Consultants
Geotech and Material Consultants
Ensure and Assure safety of the structures
For a better and safe place to live and work with strong foundation
Quality Consiousness is Our Core Concept
For a better and safe place to live and work with strong foundation
Quality Consiousness is Our Core Concept
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We have completed 20 years of our existence.
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We are now having rock exploration facilities also.
Plate Load Test as per IS: 1888-1982
The scope of this test lays down the method for conducting load test for estimation of bearing capacity of soils and its settlement at required depth of foundation.
The test consists of a Test Pit being dug of suitable requisite dimensions (as per size of plate used and depth of foundation proposed) with circular or square bearing plates of mild steel, not less than 25mm. in thickness and varying in size from 300 to 750 mm with chequered or grooved bottom with handles and centre marked placed at the centre of the Test Pit along with loading column and a Hydraulic Jack of required capacity with properly calibrated load measuring device and four nos. Dial Gauges placed on the Bearing Plate for noting dial gauges deflection readings. On top of all this is placed a loading platform supported by suitable means at least 2.5m from the test area with a height of 1 metre or more above the bottom of the pit to provide sufficient working space. No support of loading platform should be located within a distance of 3.5 times size of test plate from its centre.
The test plate shall be placed over a fine sand layer of maximum thickness 5mm, so that centre of plate coincides with the centre of reaction girder/beam. Moreover, the hydraulic jack should also be centrally placed over the plate with the loading column in between the jack and reaction beam so as to transfer load to the plate. A ball and socket arrangement is inserted so as to keep the direction of load vertical throughout the test. A minimum seating pressure is also applied and removed before starting the test.
The dial gauges’ placement should be such that the settlement is measured continuously without resetting in between.
The test location shall be based on the worst estimated conditions. In case the water table is within the depth equal to the width of the test 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 and maintained by pumping through a sump, away from the test plate, however, for cohesionless soils like silt and fine sand which cannot be drained by pumping from the sump, the test level shall also be water table level.
The Test Pit, usually at the foundation level, is of width equal to five times the test plate or block, shall have a carefully levelled and cleaned bottom at the foundation level.
The side of the test bearing plate shall be at least four times the maximum size of the soil particles present at the test location.
The load is applied to the soil in cumulative equal increments up to 1.00 T/M2 or one fifth of the estimated ultimate bearing capacity, whichever is less.
The settlements should be observed for each increment of load after an interval of 1, 2.25, 4, 6.25, 9, 16 and 25 minutes and thereafter at hourly intervals to the nearest 0.02 mm. The next increment of load shall then be applied and the observations repeated. The test shall be continued till a settlement of 25 mm. under normal circumstances or 50 mm in special cases, such as dense gravel, gravel and sand mixture is obtained or till failure occurs, whichever is earlier. Alternatively, where settlement does not reach 25 mm., the test should be continued to at least two times the estimated design pressure. If needed, rebound observations may be taken while releasing the load.
The test consists of a Test Pit being dug of suitable requisite dimensions (as per size of plate used and depth of foundation proposed) with circular or square bearing plates of mild steel, not less than 25mm. in thickness and varying in size from 300 to 750 mm with chequered or grooved bottom with handles and centre marked placed at the centre of the Test Pit along with loading column and a Hydraulic Jack of required capacity with properly calibrated load measuring device and four nos. Dial Gauges placed on the Bearing Plate for noting dial gauges deflection readings. On top of all this is placed a loading platform supported by suitable means at least 2.5m from the test area with a height of 1 metre or more above the bottom of the pit to provide sufficient working space. No support of loading platform should be located within a distance of 3.5 times size of test plate from its centre.
The test plate shall be placed over a fine sand layer of maximum thickness 5mm, so that centre of plate coincides with the centre of reaction girder/beam. Moreover, the hydraulic jack should also be centrally placed over the plate with the loading column in between the jack and reaction beam so as to transfer load to the plate. A ball and socket arrangement is inserted so as to keep the direction of load vertical throughout the test. A minimum seating pressure is also applied and removed before starting the test.
The dial gauges’ placement should be such that the settlement is measured continuously without resetting in between.
The test location shall be based on the worst estimated conditions. In case the water table is within the depth equal to the width of the test 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 and maintained by pumping through a sump, away from the test plate, however, for cohesionless soils like silt and fine sand which cannot be drained by pumping from the sump, the test level shall also be water table level.
The Test Pit, usually at the foundation level, is of width equal to five times the test plate or block, shall have a carefully levelled and cleaned bottom at the foundation level.
The side of the test bearing plate shall be at least four times the maximum size of the soil particles present at the test location.
The load is applied to the soil in cumulative equal increments up to 1.00 T/M2 or one fifth of the estimated ultimate bearing capacity, whichever is less.
The settlements should be observed for each increment of load after an interval of 1, 2.25, 4, 6.25, 9, 16 and 25 minutes and thereafter at hourly intervals to the nearest 0.02 mm. The next increment of load shall then be applied and the observations repeated. The test shall be continued till a settlement of 25 mm. under normal circumstances or 50 mm in special cases, such as dense gravel, gravel and sand mixture is obtained or till failure occurs, whichever is earlier. Alternatively, where settlement does not reach 25 mm., the test should be continued to at least two times the estimated design pressure. If needed, rebound observations may be taken while releasing the load.
Ultimate Bearing Capacity/Safe Bearing Pressure/Settlement
The load settlement curve is drawn on log-log scale with settlements as abscissa and load intensities as ordinate based on readings obtained to know about the yield point.
The Safe Bearing Pressure is then worked out from the graph corresponding to a settlement (Sp). The settlement (Sf) is also calculated from the formula as:-
Sf = Sp [ B ( Bp+0.3 ) / Bp ( B+0.3 ) ] 2
where,
B = the size of footing in metre.
Bp = size of test plate in metre,
Sp = settlement of test plate in metre, and
Sf = Settlement of footing in metre
Sf must be within safe permissible limit for the concerned footing as per IS: 1904 - 1986.
The Plate Load Test Report must also include information about natural water table, profile of test pit as well as the sub soil properties beneath the founding level from soil sample taken from a depth equal to twice the dimension of the plate.
Sf = Sp [ B ( Bp+0.3 ) / Bp ( B+0.3 ) ] 2
where,
B = the size of footing in metre.
Bp = size of test plate in metre,
Sp = settlement of test plate in metre, and
Sf = Settlement of footing in metre
Sf must be within safe permissible limit for the concerned footing as per IS: 1904 - 1986.
The Plate Load Test Report must also include information about natural water table, profile of test pit as well as the sub soil properties beneath the founding level from soil sample taken from a depth equal to twice the dimension of the plate.
