Physical simulation test on deformation and failure mechanism of soft and hard interbedded rock masses

In order to study the mechanical properties and tensile-shear failure mechanism of soft and hard interbedded rock masses，the specimens with different layer dip angles and layer thickness ratios using a physically similar simulation method and conducted uniaxial compression tests were prefabricated ， and the following conclusions were obtained：(1) the peak strength and Young's modulus of the specimens decrease first and then increase with the increase of the dip angle β . They decrease with the increase of soft-hard layer thickness ratio k. (2) Due to the local shear slip along the bedding plane，the stress-strain curves of specimens with a dip angle of 30°–45°have a large stress abrupt drop point at the early stage of loading. This is a unique multi-peak characteristic of the stress-strain curve of soft and hard interbedded rock masses. In addition，compared with the existing laminated rock failure modes，a new failure mode was found，that is，soft strata compression damage and hard strata tensile damage across the bedding plane. (3) Using a method of crack image extraction，the rose distribution map of crack characteristic evolution on the samples surface is given for the first time under different dip angles β and thickness ratio k. At the same time，the failure mechanism of tensile and shear cracks and the distribution proportion of cracks were studied，along with the influence on the specimen's failure mode. It is believed that the dip angle β controls the crack propagation direction，and the thickness ratio k determines the proportion of tensile-shear failure. Shear slip along the layer，tensile fracture in the hard layer and crushing failure in the soft layer are the three main factors leading to the deformation and failure of the samples. When the bedding plane dip angle β is around 30°–45°，the shear slip occurs at the bedding plane and the shear cracks increase. When the dip angles are near 0°and 90°，tensile failure occurs in the through layer or along the layer direction，and the shear cracks decrease. © 2023 Academia Sinica. All rights reserved.