Experimental Study of Modeling Partially Drained Dense Sand Behavior in Monotonic Triaxial Compression Loading Tests

Sand behavior is significantly affected by the drainage conditions being either fully drained, partially drained, or undrained. Partially drained conditions are often encountered in reality; however, partial drainage effects are not commonly considered at a soil element level. As a common soil element test, triaxial testing is carried out with either fully drained or undrained conditions for the shearing phase, as specified according to the soil type and design application. In this study, a series of monotonic triaxial compression tests were performed under various drainage conditions with a special filter device to investigate partially drained behavior of dense sand. Partially drained behavior resulted in simultaneous excess pore water pressure generation and volumetric strain and behaved more similar to the undrained condition at the beginning of shearing and more similar to the fully drained condition at the large strains. Using three different degrees of drainage induced by three filter devices with different steady-state flow capacity and different shearing strain rates suggest that a ratio of the axial strain rate to the filter flow capacity can be used as a unique parameter to represent degree of drainage in a partially drained test.