Macro-meso Experimental Study On Deformation And Failure Mechanism Of Jointed Rock Mass

Natural rock mass is composed of joint planes and blocks cut by joint planes,which is a complex and discrete geological body.Its failure is often directional,and its directivity often depends on the occurrence of joint planes in the rock mass.Encountered in actual underground engineering often contain different joint types of fractured rock mass,and the excavation of underground tunnel(cavity)can break the original stress balance.It leads to the presence of native ground stress redistribution and the activation of new joints or fissures in surrounding rock,making the engineering rock mass stability lower.In order that the rock mass engineering system for safe and economic design,it is necessary to study the mechanical properties of fractured rock mass,so as to scientifically understand the mechanical properties of jointed rock mass,reveal its failure mechanism,and provide theoretical guidance for engineering practice.In this thesis,the mechanical properties of jointed rock mass under different combinations of fractures were studied by physical tests and numerical simulation tests from macro and meso perspectives,and the coupling mechanism of cracks in jointed rock mass was revealed by the development and propagation path of cracks and the failure characteristics of instability.The main research contents and achievements of this thesis are as follows:(1)The macroscopic and microscopic crack evolution and mechanical properties of real rock specimens with single central fracture,collinear double boundary fracture and central-boundary three fractures were analyzed by means of physical test and particle flow numerical simulation.The aggregation effect of single central fracture tip and the variation of surrounding stress with fracture dip angle,the variation of stress concentration and dip Angle in rock bridge specimens with boundary fracture,and the influence mechanism of central fracture ? dip angle on crack initiation and propagation of boundary fracture were obtained,and the crack coupling mechanism between simple fractures was revealed.(2)Through the joint and holes-joint group contrast test of square specimen with hole joint research joint set angle between mechanical behavior relationship,won the hole joint effect on the mechanical behavior of joint set samples,including joint set specimen local section shear damage rule and joint set angle of hole joint local failure mechanism.The coupling mechanism of cracks between joint groups and the interaction mechanism between pore joints and joint groups were revealed.(3)The self-developed quasi-plane-strain casting-loading integrated mold was used to conduct unilateral in-flight loading tests on rock specimens of jointed groups,and the macroscopic failure characteristics,physical and mechanical properties and local section tension-shear failure distribution of the target specimens under different inclination angles were obtained.The difference of damage spalling behavior of local rock mass with joints in space position under axial loading without constraint on one side was revealed.