Energy storage characteristics and damage constitutive model of thermally treated granite: An experimental investigation

With the development of deep Earth energy engineering in the 21st century, the challenges brought by high stress and high temperature will become increasingly frequent. In the development of deep geothermal resources, the constitutive relationship of high-temperature rock mechanics is a core issue faced by geothermal development projects. In this paper, investigates the static mechanical behavior and brittle ductile failure characteristics of granite under heat treatment at 25, 200, 400, 600, and 800 ℃ during uniaxial compression, based on the linear energy storage rule of high-temperature rock under uniaxial compression before peak strength, we propose an energy dissipation rule post-peak, leading to an energy evolution rule for the whole failure process of high-temperature rock. Based this, the stress–strain curve characteristics of the rock after reaching the rock peak were characterized for the first time. Then, establish the corresponding constitutive model. The calculation relationship of pre-peak strain energy as the independent variable is determined by uniaxial loading and unloading test, and the model parameters are calibrated. The calculation results can better reflect the brittleness characteristics of granite and the transition from brittleness to ductility with increasing temperature, solving the problems that all previous constitutive relationships cannot reflect the post peak curve of the rock failure. The peak strength and strain observed at various temperatures align well with our experimental findings, confirming the model’s validity presented in this article, which can provide theoretical guidance for practical geothermal engineering applications.