Plate load test on stiff clay
Plate load test on stiff clay
(OP)
We are carrying out a ground investigation at a airport in UK. We specified an incremental plate load tests at 3 locations. One of the plate load test result is out. Using a 0.3 m diameter plate and a maximum load of 934kPa, the test was only carried out in 30mins. Settlement was 1.25mm. When the load was removed, the soil rebound completely i.e residual settlement is 0mm.
I feel that with this test nothing has been achieved. I am not comfortable with the results. Can someone shed more light on this test? Any guidance?
I feel that with this test nothing has been achieved. I am not comfortable with the results. Can someone shed more light on this test? Any guidance?





RE: Plate load test on stiff clay
RE: Plate load test on stiff clay
See in
PCA Soil Primer
Portland Cement Asscoiation
a nice Fig.16 showing correlations with bearing values, limit strength, classifications of the soil for various agencies and CBR (around 100).
Of course 1 point is just a point and to discard any anomalies a number of tests needs be made to get some minimum appraisal of the actual state of some wide area.
RE: Plate load test on stiff clay
Depending on what information you have been required to produce, will depend upon whether or not you can use the results. This method assesses the eleastic stiffness of the ground, the fact that you have 0mm residual settlement demonstrates the soil behaved in an elastic manner. If upon unload you had some residual settlement, then the soil did not fully recover from the load, hence not true elasticity.
Who specified the method and loads?
RE: Plate load test on stiff clay
RE: Plate load test on stiff clay
RE: Plate load test on stiff clay
BigH: iT IS PRESSURE - 934kPa. We carried out 9 window samples and 1 cable percussion borehole. Test schedule has just been prepared for the samples taken from the labs and 1-D oedometer test has been specified on U100 samples from the borehole. So no pc' valoes for now.
The investigation is under an existing airfied pavement. The clay is generally described as stiff to very stiff with corecsppnding cu values from vane test and SPT.
Two plate load tests were carried out. One of the test showed settlement of 1.7mm (the other 1.25mm) and the pressure-deformation curve seem to be levelling up and have some residual settlement of 0.16mm (the other have no residual settlement0.
RE: Plate load test on stiff clay
I have just assessed the data for the 1.25mm settlement and using a 300mm plate, the equiavlent CBR based on the equations from IAN 73/06 is 224% with a corresponding Modulus of sub-grade reaction in the order of 300MN/m²/m. More than just stiff clay!