Development of shear resistance at cohesive soil – geotextile interfaces

The shear resistance at cohesive soil – geotextile interfaces is important for the proper design of geotextile-lined structures. Although the interaction behaviour at cohesive soil – geotextile interfaces has been studied in the past, most of those research efforts have been focused primarily on the determination of the shear resistance at failure. Therefore, an attempt to quantify the development of shear resistance at the cohesive soil – geotextile interfaces with increasing shearing displacement is presented in this study. Toward this end, direct shear tests were conducted on soil – geotextile interfaces using a modified 100 mm shear box. A compacted cohesive soil of low plasticity (CL) was tested in contact with three woven and four non-woven geotextiles of five types. The direct shear tests yielded polynomial failure envelopes for the cohesive soil – geotextile interfaces, possibly indicating a transition from drained to undrained conditions at the interface with increasing normal stress. A special method for the determination of the interface shear strength parameters considering the non-linearity of the failure envelopes, is applied in the present study. The shear resistance parameters are functions of the shearing displacement at the cohesive soil – geotextile interfaces and their values at failure reveal a transition from “friction-like” behaviour to “adhesion-like” behaviour as normal stress increases.