Confining pressure effect on energy parameters of sandstones based on damage evolution

Abstract

The characteristic parameters corresponding to damage evolution state of rock material are crucial to designing, predicting and monitoring the stability of geotechnical engineering.The cyclic loading-unloading triaxial compression tests of sandstones were implemented with different confining pressure, and the damage evolution state were determined by the lateral strain method and the volumetric strain method, and the energy parameters phased evolution, the energy evolution of characteristic points corresponding to damage evolution state and relation with confining pressure, were analyzed based on damage evolution state.The result showed that:with different confining pressure, the energy parameters increased with the increase of the strain at each stage before the pre-peak;the mutation of the elastic strain energy and the dissipation energy at peak stress transferred to post-peak with the increase of the confining pressure;the energy parameters decreased to level off at residual stress stage.The energy parameters had a power function decrease with confining pressure at the point of σcc, and the dissipation energy decreased to level off with the increase of the confining pressure.At the points of σci, σcd and σp, the energy parameters increased linearly with confining pressure, and there was small change trend of the difference between the total input energy and the elastic strain energy with the confining pressure at the different characteristic points, and the relative difference between the total input energy and the elastic strain energy was minimum, and the total input energy converted into the elastic strain energy was maximum at point σcd.

Keywords

• sandstones
• damage evolution
• characteristic points
• energy parameters
• confining pressure