【摘要】 矿区边坡岩体因裂隙分布复杂、尺度效应显著及卸荷响应机制多变,面临力学参数难以等效表征、破坏机制难以准确描述等问题。采用离散元软件PFC建立DFN-DEM耦合计算模型,分析了DFN分布下试样尺寸对裂隙岩体的应力—应变曲线、破坏过程与模式和表征单元体(REV)尺寸及力学参数值的影响,并探究了REV尺寸下试样的卸荷破坏过程。研究结果表明:随着试样尺寸增大,裂隙数量增加了结构的非均质性,其破坏特征由塑性主导的延性破坏逐渐过渡为弹性主导的脆性破坏;随着试样尺寸增大,裂隙岩体的破坏模式由集中脆性破坏逐渐演化为多区协同的渐进式破坏;单轴抗压强度随尺寸增大呈负指数衰减,弹性模量则先波动后趋于稳定。在此DFN分布下裂隙岩体的REV尺寸为11 m×22 m,REV单轴抗压强度为9.21 MPa,弹性模量为27.9 GPa;卸荷过程经历加载、应力维持、逐步破坏和最终破裂4个阶段,且围压越大,卸荷后结构越不稳定,裂纹扩展和力链瓦解越迅速。研究成果可为矿区离散裂隙边坡力学参数取值与稳定性分析提供一定的帮助。更多还原

【Abstract】 Due to the complex fracture distribution,significant scale effect and variable unloading response mechanism,the slope rock mass in the mining area is faced with the problems that the mechanical parameters are difficult to be equivalently characterized and the failure mechanism is difficult to be accurately described. The discrete element software PFC was used to establish the DFN-DEM coupling calculation model. The influence of sample size on the stress-strain curve,failure process and mode of fractured rock mass and representative elementary volume(REV) size and mechanical parameter values under DFN distribution was analyzed. The unloading failure process of the sample under REV size was explored. The results show that with the increase of sample size,the number of cracks increases the heterogeneity of the structure,and the failure characteristics gradually change from ductile failure dominated by plasticity to brittle failure dominated by elasticity. With the increase of sample size,the failure mode of fractured rock mass gradually evolved from concentrated brittle failure to multi-zone synergistic progressive failure. The uniaxial compressive strength decreases exponentially with the increase of size,while the elastic modulus fluctuates first and then tends to be stable. Under this DFN distribution,the REV size of fractured rock mass is 11 m×22 m,the uniaxial compressive strength of REV is 9. 21 MPa,and the elastic modulus is 27. 9 GPa. The unloading process undergoes four stages:loading,stress maintenance,progressive failure and final fracture. The larger the confining pressure is,the more unstable the structure is after unloading,and the faster the crack propagation and force chain collapse are. The research results can provide some help for the mechanical parameter value and stability analysis of discrete fracture slope in mining area.更多还原