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.