EXPERIMENTAL INVESTIGATION OF TIME-DEPENDENT EFFECT ON SHEAR STRENGTH PARAMETERS OF SAND- GEOTEXTILE INTERFACE

The time-dependent behavior of soils has been investigated extensively using one-dimensional and triaxial tests. The phenomena associated with time effects in soils are creep, relaxation, strain rate and re-arrangement effects. The engineering properties of soil are often improved significantly with the elapse of time. The objective of this paper is to investigate the time-dependent effect on the shear strength parameters of sand–geosynthetic interface using large direct shear test apparatus. For this purpose, the geotextile layer was carefully adhered to a piece of rigid block with a thickness such that half of the shear test box is occupied. The other half of the box has been filled with sand and the test performed. Three normal stresses of 30, 45, and 60 kPa have been applied in all tests. The shear stress has subsequently been applied at different times to the failure stage. In all tests, the shearing velocity has been kept the same. The results of these experiments show that the stiffness and friction angle of the sand–geotextile interface increases up to 35% and 5.5% at 720 minutes after the sample is poured in the mold. These increases occur mostly in the first two hours following the normal stress application to the samples. The findings in this paper are interesting to consider in practice.