Measuring and Modelling Cyclic Response of Dense Sand Under Partially Drained Conditions

Cyclic laboratory tests on sand are generally performed either under drained or undrained conditions, while the actual in-situ conditions typically are partially drained. It is therefore necessary to make some assumptions in order to use the cyclic properties obtained from these tests in design. To check the consequence of these assumptions some special cyclic triaxial tests with different degree of drainage are therefore carried out at NGI. This paper presents the results from these tests together with a detailed interpretation. It is shown that the measured accumulated pore pressure and volumetric strain may be very well back-calculated by three basic equations. The accumulated volumetric strain during a cycle is the key material property, together with a represented bulk modulus and the flow resistance of the special filter device. Based on the results, it is concluded that more study is required to fully understand the governing properties that controls the accumulated strains, especially the effect of previous stress or strain history.