A simple shear strength model for interlayer shear weakness zone

Interlayer shear weakness zone (ISWZ) is a widespread zonal weak geotechnical system with variable thickness in rock masses, representing a potential threat to the overall stability of structure constructed on or within the rock mass due to their relatively poor mechanical properties. Its shear behaviour depends on both the interlayer soil and the interlayer soil/host rock interface (soil/rock interface). In this study a dynamic approach is adopted by treating ISWZ as an unfilled joint (rock/rock interface) that is increasingly filled with interlayer soil of variable thickness. Based on the available experimental data, a simple shear strength model is developed, capable of describing both the shear behaviours of interlayer soil and soil/rock interface. Because the geometric factors (i.e., the thickness of interlayer soil and the morphology of interface) and the mechanical conditions (i.e., normal stress, uniaxial compressive strength of rock and shear strength of interlayer soil) are all taken into account, the combining mechanical effect of interlayer soil and soil/rock interface on the ISWZ is totally included in the model. This is partly confirmed by the good agreement between the model prediction and the experimental results from laboratory and field tests.