增强型地热系统(EGS)是目前开发干热岩的关键技术手段，在EGS的建设与运行过程中，储层岩石会遇到高温冷却、循环冷却、遇水冷却等多种冷却条件。因此，研究不同冷却条件下花岗岩(典型干热岩)的力学响应特征意义重大。

(1) 总结并分析了不同冷却条件(高温自然冷却、遇水冷却、循环冷却)下我国典型花岗岩在力学响应(单轴抗压强度σ_c、弹性模量E、抗拉强度σ_t和泊松比ν)方面的实验数据，指出温度低于200或300 ℃时，高温自然冷却后花岗岩的σ_c、E和σ_t略有降低；温度高于200或300 ℃时，σ_c、E和σ_t随温度升高近线性减小。(2) 在任意温度下，遇水冷却后花岗岩σ_c、E和σ_t随温度的升高近线性减小。循环冷却下，在经历第1次循环后花岗岩σ_c、E和σ_t迅速降低，而当循环次数大于5时，σ_c、E和σ_t逐渐趋于定值。高温自然冷却下，ν随温度升高而降低，其降幅大于高温遇水冷却条件下的ν。(3) 高温花岗岩在不同冷却条件下力学性能劣化的主因是内部微裂纹的起裂和扩展。统计了不同冷却条件下干热花岗岩力学响应数据并分析其内在机理，对力学参数归一化值与温度的关系进行拟合，并提出了经验公式。

提出高温花岗岩岩石力学研究的未来发展趋势，包括干热岩开采与CO₂地质封存结合过程中的力学响应、多场−多相−多过程耦合作用下干热岩力学响应、基于干热岩开发过程中的实际条件开展实验研究等，以期为干热岩开发的相关设计、计算和数值模拟提供理论支撑。

Enhanced geothermal systems (EGSs) serve as a key technique for exploiting hot dry rocks (HDRs) presently. During the construction and operation of EGSs, rocks of the HDR reservoirs will experience various cooling conditions, such as natural cooling, cyclic cooling, and water cooling, rendering it greatly significant to investigate the mechanical response characteristics of granites—typical HDRs—under varying cooling conditions.

This study offers a summary and analysis of experimental data about the mechanical responses, i.e., uniaxial compressive strength (σ_c), elastic modulus (E), tensile strength (σ_t), and Poisson's ratio (ν), of typical granites in China under varying cooling conditions including natural, water, and cyclic cooling. The results reveal that after natural cooling, the σ_c, E, and σ_t values of the granites decrease slightly at temperatures below 200 ℃ or 300 ℃ but decrease nearly linearly with an increase in temperature at temperatures greater than 200 ℃ or 300 ℃. After water cooling, these values decrease nearly linearly with an increase in the temperature at any temperature. Under cyclic cooling, these values decrease rapidly after cooling for the first time and then gradually tend to remain constant after more than five times of cooling. Under natural cooling, the value of ν decreases with a rise in temperature, with the decreasing amplitude greater than that under water cooling. The deterioration of the mechanical properties of high-temperature granites under varying cooling conditions is primarily due to the generation and propagation of microcracks in them. Based on the statistics and the internal mechanism analysis of the mechanical response data on hot dry granites under varying cooling conditions, this study conducts the fitting of normalized mechanical parameters with temperature and proposes relevant empirical formulas.

This study proposes that future research on the mechanical properties of high-temperature granites will focus on the mechanical responses of HDR during their exploitation combined with CO₂ sequestration, the mechanical responses of HDRs under the coupling effects of multiple fields, phases, and processes, and experimental studies based on the actual conditions of HDR exploitation. All these are expected to provide some theoretical support for the design, calculation, and numerical simulation of HDR exploitation.