Evaluation of sand-geotextile interface friction angle by a modified 300x300mm direct shear box

摘要

The design and fabrication of a metallic system which can be installed in the large shear box (300mm x 300mm) of a 100 kN direct shear machine and make it appropriate for running interface shear tests between geosynthetic-soil and geosynthetic-geosynthetic, is presented. Results are also presented of shear tests preformed with the modified shear box on interfaces between Ottawa 20-30 sand, with a void ratio e≈0.50 (D_r=95%), and a nonwoven needlepunched geotextile of four different densities. The tests were conducted under normal stresses of 45, 110, 165 and 220 kPa. The shear resistance at the interface, and the vertical displacement, were recorded during testing up to horizontal displacements of 25mm. The test results indicate that the apparent interface friction angle is independent of the geotextile density and equal to δ=0.86Φ, where Φ= peak angle of shear resistance of sand.