Research On Mechanical Properties And Crack Growth Law Of Cross-Fractured Rock-Like Materials

Rock mass is an anisotropic brittle engineering material composed of rocks(structures)and structural planes with different compositions.Under the complex and long-term geological action,various micro-defects have been bred in the rock mass.Under the action of various engineering activities(excavation,blasting)and complex in-situ stress,these micro-defects gradually develop into discontinuous surfaces such as macro-joints and faults.These defects will weaken the mechanical strength of the rock mass and change its deformation characteristics.It greatly affects the stability of rock mass engineering.Therefore,it is of great significance to study the instability failure and crack propagation of fractured rock mass under stress conditions.In this paper,the prefabricated cross-fracture-like rock materials are prepared as the research object,and the RYL-600 rock shear rheometer is used to conduct uniaxial compression experiments on the specimens.Combined with the static strain gauge,the strain at the tip of the crack is collected,and the PFC numerical simulation software is used to simulate,and then the influence of the crack inclination and the intersection angle on the mechanical properties of the specimen and the crack propagation law is analyzed,and the following main conclusions are drawn:(1)The cross-fractured rock specimen under uniaxial compression has experienced four stages: the crack compaction stage,the elastic deformation stage,the unstable fracture development stage,and the post-fracture stage.The stress-strain curve conforms to the deformation characteristics of plastic-elastic-plastic rock mass.Compared with the intact specimen,the peak strength of the fractured specimen is reduced to varying degrees.(2)When the cross angle β is fixed at 90°(orthogonal),with the increase of the inclination angle of the crack,the peak strength of the specimen shows a distribution law that first decreases and then increases;When the inclination angle α of the crack remains unchanged,with the increase of the cross angle β,the peak strength of the specimen shows a variation law of first increasing and then decreasing;When there is a crack in the cross crack and the loading direction is the same,the peak strength of the specimen is obviously larger,and the weakening effect of this crack on the specimen is small.(3)Combined with numerical simulation and analysis of the evolution law of local strain at the crack tip,the local strain distribution at the crack tip of the cross-crack specimen and the evolution law of crack initiation,propagation and penetration during compression failure are summarized.When the intersection angle is constant,wing-shaped cracks firstly occur at the long crack tip of the orthogonal crack specimen,and then expand to the short crack tip or the end of the specimen to form a macroscopic fracture zone.When the inclination angle of the crack remains unchanged,most of the cross-crack specimens start to crack at the tip of the long crack,and gradually expand to the end of the specimen,and finally break through.