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.