Weakening effects of occurrence structural plane on mechanical properties of silty mudstone

The structural plane has a weakening effect on the physical and mechanical properties of rock mass, which directly affects the stability of rock projects. Taking silty mudstone of surrounding rock of coal mine roadway as the research object, the quasi-static uniaxial loading tests and the uniaxial cyclic loading and unloading tests are performed on the rock specimens with different dip angles. The digital images of the overall process of loading and deformation are collected synchronously by the speckle system, and the mechanical properties and strain field evolution characteristics of rock specimens under the influences of weakening of structural plane with different dips are analyzed. The results show that the weakening effects of structural plane on the stress and deformation of silty mudstone are obvious, especially with the tread approaching to 60°. Under the quasi-static uniaxial loading, the stress-strain curves of the occurrence specimens with dip angles of 45° and 60° show double peaks due to the weakening of the filling media on the structural plane. The parameters of deformation localizing length ratios of structural plane and rock specimens are put forward, and quantitative analysis of strain evolution is performed to determine the contribution of deformation of structural plane and rock specimens to their overall deformation. Besides, compared with the quasi-static uniaxial loading tests, the cyclic loading and unloading tests improve the dominance of failure of structural plane, which thus significantly reduces the peak strength of specimens.