Field determination of stress-strain relations of clay till

Swedish clay till is a heterogeneous material varying greatly both in the horizontal and vertical directions of a deposit. The determination of stress-strain relations for e.g. prediction of settlements and bearing capacity based on allowable settlement criteria is therefore difficult and requires a large volume of soil to be tested in order to be relevant. The paper describes the results of pressuremeter tests performed with both Menard equipment and new equipment designed along the guidelines given by Briaud (1992). The tests with the latter equipment were carried out broadly in accordance with the same guidelines enabling evaluation of the modulus at unloading and reloading, its dependence on stress level and strain level in the cycle, and the time dependence (creep effects) on the results. After the tests, a series of medium to large scale plate load tests was performed. The results were compared to the load settlement curves predicted using the Briaud (1995) method for the Menard pressuremeter test results as well as a calculation procedure proposed by Ekdahl and Bengtsson (1996) for the results from the new equipment. The correspondence varied for the different plates, which can partly be attributed to the heterogeneity of the soil. However, the results showed that both the new procedure, and the Briaud (1995) procedure with some modifications, can be used to predict both settlements and bearing capacity based on settlement criteria of footings on clay till.