Experiment And DEM Simulation On Mechanical Behavior Of Non-persistently Jointed Rock Mass Containing Circular Opening

Rock mass is a complex geological medium formed during the long geological tectonic movement.Most naturally occurring rock masses consist of different types of intact rock and structural planes including schistosity,fissures,joints,faults,bedding planes,etc.The presence of such discontinuities such as cracks and joints significantly reduces the mechanical properties of the rock mass.Most of today's underground constructions(eg,hydropower or traffic tunnels,dam foundations,mining chambers,nuclear waste repository,etc.)are mostly built in intact rock masses or intermittent jointed rock mass.Disturbance of rock engineering often causes crack initiation,propagation,and coalescence of non-persistent joints,which would result in the instability of surrounding rock.It is crucial to scientifically understand the strength,deformation,and failure mechanisms of the non-persistent jointed rock mass in order to achieve safe and economical engineering design.In this paper,the strength,deformation and failure behavior of rock-like specimens of non-persistently jointed rock mass containing circular opening are discussed through physical modelling and numerical simulation.Detailed research work is as follows:(1)Uniaxial compression tests assisted by acoustic emission and three-dimensional digital speckle technology were conducted on the specimens of non-persistently jointed rock mass containing circular opening.So,the strength,deformation,failue process and AE characteristics under uniaxial compression were analysed in detail.(2)The parallel-bonded model in PFC is used to establish numerical models for standard cylindrical specimens.Then,the sensitivity of model mesoscopic parameters(such as contact modulus,stiffness ratio,cohesion,friction angle,and particle friction coefficient)was analyzed,and the effect of various mesoscopic parameters on rock strength,deformation,and failure characteristics was clarified.This lays the foundation for the correct and reasonable mesoscopic parameters selection and subsequent simulation work.(3)Based on the triaxial compression tests of rock-like specimens,the correct and reasonable PFC mesoscopic parameters were selected and the simulation procedure for non-persistently jointed rock mass containing circular opening was established.Based on the results comparison between numerical simulation and physical modelling,the mechanical effects of joint geometric parameters(such as dip,spacing,continuity factor),hole's diameter and confining pressure on the strength and deformation characteristics are systematically studied.The hole's failure modes and failure mechanisms under different structural parameters were discussed in detail.