Study on the Mechanical Failure Behavior and Anchoring Control Effect of Non-persistent Jointed Rock

Author:Chen Zuo

Supervisor:yang sheng qi


Degree Year:2019





A large number of engineering practices show that the failure of rock mass engineering is usually caused by the carck propagation and coalescence of the original joints in the surrounding rock under the action of environmental stress,and the bolt shows obvious reinforcement effect in the support of jointed rock mass.Therefore,it is of great significance to investigate the deformation and failure characteristics of non-persistent jointed rock mass and the anchoring effect on crack prevention.This thesis was supported by the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars(No.BK20150005)and Key Project of Natural Science Foundation of China(No.51734009),which was focused on solving the scientific problem of stability control of jointed rock mass.Laboratory experiment,numerical modelling,theoretical analysis and engineering practice were applied to investigate the failure behaviours and anchoring effect of non-persistent jointed rock mass.The main results are presented as follows:(1)The non-persistent jointed rock specimens were prepared by using rock-like materials.The uniaxial compression experiments were carried out on the specimens,the strength and deformation characteristics of the specimens with different joint inclinations were analyzed,the real-time strain field and AE events evolution process of the specimen during loading were obtained with digital speckle correlation method(DSCM)and acoustic emission test system,and the change in stress state of the specimen caused by strain localization is discussed,five failure modes of specimens containing non-persistent joints under the influence of joints inclination are revealed.(2)The uniaxial compression test of anchored specimens containing non-persistent joints under different anchoring conditions were carried out.The influence of anchoring type,pre-tightening force and joints inclination on the mechanical response characteristics of anchored jointed rock mass were studied,the quantitative effects of bolt reinforcement on mechanical behavior,strength parameters and deformation characteristics of anchored specimens are discussed,and the influence of bolts on post-peak brittleness index of jointed rock masses were also analyzed.(3)By using DSCM,AE monitoring system and bolt axial force monitoring system,the damage evolution of anchored specimens containing non-persistent joints were studied,the influence of joints inclination and pre-tightening force on the damage evolution and failure modes of anchored specimens,the relationship between bolt axial force and stability of"bolt-jointed rock mass"composite bearing structure during loading is revealed.The X-ray CT scanning system was combined with the Avizo software to reconstruct the internal fracture surface of the fractured specimen.The influence of the bolt on the internal crack of the jointed rock mass was analyzed,and the reinforcing effect and crack prevention mechanism of bolt on the jointed rock mass was revealed.(4)The Particle Flow Code(PFC3D)was adopted to establish the numerical model of specimens containing non-persistent joints,the micro-mechanical parameters were calibrated through a trial amd error process based on the results of physical experiment.The mechanical behavior of specimens containing non-persistent joints under different anchoring conditions are obtained,and the influence of bolt on the microcrack evolution process and displacement vector field are analyzed,which can deepened the understanding of reinforcement effect of jointed rock mass under the action of prestressed bolts.(5)Taking the roadway with soft and jointed surrounding rock as the engineering background,the rock mass parameters were evaluated using geological strength index(GSI)based on the field data amd the mechanical properties.The Universal Discrete Element Code(UDEC)was adopted to establish the numerical model of a ventilation roadway in Xin’an coal mine,and the micro-parameter calibration is conducted with the rock mass properties.The failure process of roadway under unsupported and primary support conditions is simulated;the deformation,stress and crack evolution characteristics were clearly illustrated,A new“bolt-cable-mesh-shotcrete+shell”combined support is proposed to support the ventilation roadway.The numerical simulation and monitoring data show that the large deformation has been effectively controlled with the new support design.There are 132 figures,26 tables and 213 references in this dissertation