循环加卸载下大理岩渐进损伤的能量特性研究

Energy characteristics of progressive damage of Jinping marble under cyclic loading and unloading

为探究锦屏大理岩渐进损伤过程中的能量特性,开展了5种围压下岩样的三轴循环加卸载试验,分析了循环加卸载下大理岩渐进损伤的弹性模量演化、能量演化及分配规律、能量演化的围压效应、损伤演进特性,并系统剖析探讨了基于能耗比和能耗差定义的两种岩石强度失效的能量判据。研究结果表明:大理岩从初始屈服到进入残余阶段的整个变形破坏过程中,加载段弹性模量和卸载段弹性模量均呈现单调退化的弹塑性耦合特征,应避免采用弹性模量不变假定计算弹性应变能带来的偏差;围压升高不仅能够有效提升大理岩的吸能和储能效率,也能强化大理岩的吸能和储能极限,同时还能抑制大理岩的能量耗散效率和耗散能的提升幅度;岩样从峰前到峰后的能量演化是一个弹性能占比逐渐降低,耗散能占比逐渐升高的过程,残余阶段能量占比趋于稳定,其残余弹性能和残余耗散能均随着围压的增加呈现近似线性的增长,而最大弹性能和最大耗散能则随着围压的增加呈现非线性的增长。考虑初始损伤和残余承载力修正的损伤演化方程能很好地捕捉不同围压下岩样基于耗散能定义的损伤变量的变化特征。进而,基于能量相对比例定义的能耗比判据可视为大理岩的材料失效判据,基于能量绝对差值定义的能耗差判据可视为大理岩的结构失效判据。

In order to investigate the energy characteristics of Jinping marble during progressive damage,triaxial cyclic loading and unloading tests on marble samples under five different confining pressures were carried out.The evolution of elastic modulus,the rule of energy evolution and distribution,the effect of confining pressure on energy evolution,and the characteristics of progressive damage evolution of marble under cyclic loading and unloading were analyzed.Furthermore,the energy failure criteria of rock strength based on energy consumption ratio and energy consumption difference were systematically discussed.The results show that both the loading and unloading elastic moduli of the marble are monotonically degraded during the whole deformation and failure process from the initial yielding to the residual stage.The deviation of elastic strain energy calculation with the assumption of constant modulus of elasticity should be avoided.The increase of confining pressure can not only effectively enhance marble's energy absorption and storage efficiency,but also strengthen marble's energy absorption and storage limit.It can also restrain marble's energy dissipation efficiency and the increase amplitude of dissipation energy.The ratio of elastic energy decreases and the ratio of dissipative energy increases from pre-peak to post-peak,and the ratio of residual energy tends to be stable.The residual elastic energy and the residual dissipated energy increase approximately linearly with the increase of confining pressure,while the maximum elastic energy and the maximum dissipated energy increase nonlinearly with the increase of confining pressure.The modified damage evolution equation considering initial damage and residual bearing capacity can well capture the variation characteristics of damage variable based on dissipative energy under different confining pressures.The criterion of energy consumption ratio based on the definition of energy relative proportion can be regarded as the criterion of failure of marble material.While the criterion of energy consumption difference based on the definition of absolute difference of energy can be regarded as the criterion of failure of marble structure.