Soil-geosynthetic interface shear behaviour: Insights from inclined plane and direct shear tests

Abstract

The assessment of soil-geosynthetic interface shear strength properties is essential for the safe design of geosynthetic-reinforced soil systems. In this study, a series of inclined plane and direct shear tests was carried out to evaluate the shear strength parameters of the interfaces between a residual soil from granite and two different geosynthetics: an extruded geogrid and a geocomposite reinforcement. The influence of soil moisture content was analysed under inclined plane and direct shear modes by compacting the soil at the optimum moisture content (wopt) and 2% wet of the wopt. The direct shear test results show that the increase in soil moisture content may lead to a considerable reduction in the apparent cohesion of the soil-geosynthetic interface. In general, higher shear stresses were reached at the interface involving the geocomposite reinforcement. Moreover, the interface shear strength parameters established from direct shear test results generally exceeded those obtained by inclined plane tests, particularly in terms of the apparent cohesion value.