单轴压缩下不同长度单裂隙岩体能量损伤演化机制

Energy Damage Evolution Mechanism of Single Jointed Rock Mass with Different Lengths Under Uniaxial Compression

为探寻裂隙岩体变形破坏过程中内在的能量演化机制,基于岩石能量耗散理论和室内试验数据,研究了单轴压缩条件下单裂隙岩体变形破坏过程中各能量指标(总能量、弹性应变能及耗散能)演化规律,分析了裂隙长度变化对岩样力学特性、破坏模式、各能量指标及峰前能量突变幅度的影响规律。研究结果表明:裂隙岩体的峰值强度、峰值应变及弹性模量均随裂隙长度增大呈逐渐减小趋势,岩样最终的破坏模式主要为拉剪复合破坏;依据岩样变形破坏过程中耗散能演化规律可将裂隙岩体受荷能量损伤划分为初始损伤阶段、稳定损伤阶段、损伤平稳阶段、突变损伤阶段、加速损伤阶段及损伤破坏阶段6个阶段;峰值点岩样的总能量、弹性应变能及耗散能均随裂隙长度的增大而逐渐减小,但耗散能减小幅度最小;储能极限随裂隙长度变化拟合公式符合指数递减规律;岩样峰前能量突变幅度随着裂隙长度的增加而逐渐减小,且能量突变幅度越大,引起裂纹损伤扩展程度越严重。研究成果对于深化认识裂隙岩体的能量演化机制具有重要的理论价值和实际意义。

The essence of the deformation and failure of a jointed rock mass depends on energy accumulation and release. Faults,joints,and fractures are widely distributed in natural rocks,and the existence of these discontinuous surfaces greatly affects the mechanical properties and law of energy evolution of rock masses. To explore the energy evolution mechanism of a jointed rock mass in the process of deformation and failure,the evolution of energy indexes( total energy,elastic strain energy,and dissipated energy) of single jointed rock mass under uniaxial compression was studied based on rock energy dissipation theory and indoor experiment data. Furthermore,the influence of crack length on mechanical properties,failure mode,energy index,and energy mutation amplitude of a jointed rock mass were analyzed. The obtained results show that the axial peak strength,peak strain,and elastic modulus of the joined rock mass gradually decrease with the increase of crack length. The ultimate failure model of the rock sample is mainly tensile-shear complex failure. The energy damage of jointed rock mass under loading can be divided into six stages( initial damage stage,stable damage stage,damage stationary stage,mutational damage stage,accelerated damage stage,and damage failure stage) according to the law of dissipated energy evolution in the process of deformation and failure of a rock sample. The total energy,elastic strain energy,and dissipated energy of rock samples at a peak point decrease with the increase of crack length;however,the decreasing amplitude of dissipation energy is relatively small. In addition,the fitting formula of energy storage limit with the change of crack length conforms to the law of exponential decline. The energy mutation amplitude of jointed rock mass before peak value decreases with the increase of crack length,and the crack damage propagation develops more seriously by increasing the energy mutation amplitude. The research results have important theoretical value and practical significance for deeply understanding the energy evolution mechanism of jointed rock masses.