真三轴加卸载下含裂缝砂岩能量演化规律研究

为了探明真三轴循环加卸载过程中含裂缝砂岩能量演化规律,设计了真三轴循环加卸载试验,深入分析了循环加卸载过程中吸收总能量、弹性能、耗散能的演化规律与变化特征,进而探讨了能量耗散与岩石强度之间的关系。结果表明:(1)吸收总能量、弹性能和耗散能变化规律与砂岩试样裂缝角度无关,均随循环次数的增加而增加,且增幅越来越大,临近破坏时最大;(2)不同裂缝角度砂岩的吸收总能量、弹性能和耗散能与应力上限呈二次函数关系增长,吸收总能量、弹性能和耗散能能量增速依次减小,但前两者增速显著大于耗散能增速,且耗散能拟合曲线呈“凹”形;(3)定义了表征岩石储能能力和能量耗散能力的储能系数和能量耗散系数,对比发现岩石裂缝角度越大,储能能力越强,能量耗散能力越弱,岩石的峰值强度越大。

Study on Energy Evolution Law of Sandstone with Cracks at Different Angles under Actual Triaxial Cyclic Loading and Unloading

An actual triaxial loading and unloading cyclic test was designed according to the actual stress environment to explore the law of energy evolution in processing actual triaxial loading and unloading cyclic. The total energy absorption, elastic energy, and dissipated energy during the loading and unloading cyclic process were analyzed. Four terms include the evolution law and change characteristics; the relationship between energy dissipation and rock strength is discussed. The results show that: (1) The change law of total absorbed energy, elastic energy, and dissipated energy has nothing to do with the crack angle of the sandstone sample; they all increase with increasing the number of cycles, the increase is more significant, and the failure prone to occur near the maximum; (2) The total absorbed energy, elastic energy, and dissipated energy of sandstone with different fracture angles increase in a quadratic function relationship with the upper-stress limit, and the growth rate of total absorbed energy, elastic energy and dissipated energy decreases sequentially, but the growth rate of the first two is significantly greater than the dissipated energy growth rate, and the dissipated energy fitting curve is "concave"; (3) The energy storage coefficient and energy dissipation coefficient that characterizes the energy storage capacity and energy dissipation capacity of the rock are defined. More significant, the stronger the energy storage capacity, the weaker the energy dissipation capacity, and the greater the peak strength of the rock.