Method of energy evolution of rock under uniaxial compression test

In order to investigate the sandstone energy evolution behavior under the unconfined compressive condition,with the same loading rate,the uniaxial graded loading and unloading tests and unconfined compressive tests were carried out by using the RMT-150b rock mechanics tests system. Based on the research of crack generation and growth model,assuming that fatigue damage and interface friction between cracks have no effect on the elastic energy,it can be considered that the elastic energy is equal when the load of uniaxial compression is equal to the load of uniaxial graded loading and unloading. Based on the above assumptions,the elastic property,dissipated energy,elastic energy proportion to the total energy,dissipated energy proportion to the total energy,the ratio of elastic energy to dissipated energy and so on in the process of uniaxial compression were analyzed. The performance evolution of red sandstone under uniaxial cyclic loading and unloading was used to verify the correctness of this hypothesis. The research results show that ① Through the analysis of the evolution law of energy during the uniaxial compression test,it is found that the plastic dissipated energy,elastic energy and hysteretic effect dissipated energy exist at each stage of the uniaxial compression test of rock;② Some partial hysteretic effects can be stored in the rock and increase linearly with the increase of load;③ The growth rates of elastic energy and plastic energy increase as the load increases. By means of ratio analysis of elastic energy and dissipation energy,within different load ranges,the growth rates of rock elastic energy and dissipation energy can be compared in real time. When the rock strength reaches 80% ,the ratio of rock elastic energy and dissipation energy can reach its maximum,and be equal to the elastic energy index,which indicates that the analysis method of rock energy real-time evolution trend analysis has certain rationality;④ Through the uniaxial cyclic loading and unloading test analysis of red sandstone,it is found that the interface friction between fatigue damage and crack will produce plastic deformation,which causes the rock loading and unloading curve to gradually shift to the right,and has no impact on the elastic energy;and ⑤ According to the energy evolution law in the uniaxial compression test process during the analysis of elastic energy at each unloading point of uniaxial graded loading and unloading tests,and the elastic energy evolution law of uniaxial cyclic loading and unloading test is used to verify the correctness of the analysis method.