Energy storage and dissipation characteristics of red sandstone in triaxial compression tests under constant confining pressure

To investigate the energy storage and dissipation characteristics of rock material in triaxial compression tests under constant confining pressure, a series of triaxial single-cyclic loading-unloading compression tests were conducted on red sandstone specimens under eight confining pressures. Using the method of graphic area integration, the input energy density, elastic energy density, and dissipative energy density of the specimen in axial, circumferential, and total directions were obtained. The results indicate that the input energy density in the axial direction accounts for the largest logarithmic proportion of the total input energy density and that the relationship between all the parameters of the energy density and the unloading level can be described by the quadratic function. In the axial direction, a linear function relationship exists among elastic, dissipative, and input energy densities. In the circumferential direction, a quadratic function relationship exists among elastic, dissipative, and input energy densities. For the total energy parameters of the sample, the relationship of elastic, dissipative, and input energy densities conforms to the quadratic function, providing a new method for the accurate estimation of the energy parameters in the rock under high stress.