Abstract: Direct shear test was conducted on the contact interface between medium-fine sand and polymethyl methacrylate to investigate the interfacial shear properties of test materials and polymethyl methacrylate. The stress-strain curves under different normal stresses were compared and were divided into two stages, namely, the pre-peak stage and the post-peak stage with the peak strength as boundary. A shear model suitable for the interface between medium-fine sand and polymethyl methacrylate was established, and the model parameters were obtained via test data analysis and were compared with measured data. Results revealed that with the increase of strain or shear displacement, the shear process displayed obvious strain-softening effect on the interface between medium-fine sand and polymethyl methacrylate. The envelopes of peak strength and residual strength of the interface can be calculated by using Mohr-coulomb strength criterion, with the corresponding peak friction angle reaching 28.3° and the residual friction angle 24.1°. The pre-peak and post-peak model constructed by using the parameters obtained in the study could fit the experimental data well, hence providing a reference for physical simulation test design of geological hazards and shear behavior modeling of materials' contact interface.

Key words: medium-fine sand, shear behaviour, interface model, direct shear test, polymethyl methacrylate