热冲击作用下花岗岩宏细观破裂规律的实验研究

Thermal stimulation is an effective means for the permeability reconstruction and the improvement of heat transfer capacity of hot dry rock geothermal artificial heat reservoirs, which essence is thermal shock lead to rock failure. Thermal shock fracture of rock is a process in which thermal shock stress caused by unsteady heat transfer instantaneously leads to the initiation, expansion, coalescence, and destruction of cracks, which is different from thermal cracking. The project intends to start from the laws of temperature gradient change that is the core problem of unsteady heat transfer about thermal shock fracture, and introduce the thermal shock factor and use simultaneously thermal shock precision experiments and fractal, damage theory. The contents of the meso-macro level experimental research are as follows: (1) Study the unsteady heat transfer laws, meso-fracture characteristics, and macroscopic mechanical properties of granite during thermal shock failure. (2)Study the correlation regulation between the mechanical parameters of granite under thermal shock damage, such as elastic modulus, Poisson's ratio, compressive strength, tensile strength, shear strength and permeability coefficient, and thermal shock factor. (3) Study the law of meso-macroscopic damage evolution and zonal disintegration. The experimental results reveal the meso-macroscopic fracture characteristics of granite under different thermal shock rate and temperature gradient; results also reveal the evolution laws of macroscopic mechanical properties of granite under thermal shock damage. It can establish quantitative relationships between macroscopic mechanical parameters of granites under thermal shock damaged and thermal shock factor. The research results can provide technical support for the development of hot dry rock drilling and artificial heat reservoirs construction, enriching and developing the theory of high temperature rock mechanics.

热激发是干热岩地热人工热储渗透性改造、换热能力提升的有效手段，其实质就是岩石热冲击破裂。岩石热冲击破裂区别于热破裂，是一个由非定常传热引起瞬间冲击热应力，导致裂隙的萌生、扩展、贯通，从微观损伤到宏观破坏的过程。项目拟从热冲击破裂非定常传热的核心问题—温度梯度变化规律出发，引入热冲击因子，采用同步热冲击精确试验，结合分形、损伤理论，从宏细观层面实验研究花岗岩热冲击破裂过程的非定常传热规律、细观破裂特征、宏观力学特性，研究热冲击损伤花岗岩的力学参数如弹性模量、泊松比、抗压强度、抗拉强度、抗剪强度、渗透系数与热冲击因子的相关规律，以及细—宏观损伤演化和破裂分区规律，揭示不同热冲击速度和温度梯度下花岗岩宏细观破裂特征，获得热冲击损伤花岗岩的宏观力学特性演变规律，建立热冲击损伤花岗岩宏观力学参量与热冲击因子的定量关系。研究结果可为干热岩开发钻井与人工热储建造提供技术支持，丰富和发展高温岩石力学理论。

岩石热冲击破裂是一个由非定常传热引起瞬间冲击热应力，导致裂隙的萌生、扩展、贯通，从微观损伤到宏观破坏的过程，传热、细观破裂、宏观力学三者密切相关。.项目从热冲击破裂非定常传热的核心问题—温度梯度变化规律出发，引入热冲击因子来描述传热及热冲击破坏能力，采用热冲击精确试验，辅以数值模拟，对花岗岩、砂岩、石灰岩在缓慢加热到高温后急速冷却、液氮急速深冷冲击、瞬态高温热冲击方式下的非定常传热规律进行研究，揭示了热冲击非定常传热过程岩体中温度场及温度梯度演变规律。采用CT扫描技术，结合分形、损伤理论，从细观层面，揭示了热冲击作用下岩石细观破裂特征与破裂分区规律，获得了不同热冲击速度下非定常传热温度梯度与细观破裂特征相关规律。借助宏观力学试验手段，对热冲击作用下岩石的宏观力学特性及其损伤演变规律进行研究，获得了花岗岩的力学参数如弹性模量、泊松比、抗压强度、抗拉强度、抗剪强度、渗透系数与热冲击因子的相关规律，建立热冲击作用下花岗岩宏观力学参量与热冲击因子的定量关系、以及原位应力状态花岗岩热冲击破裂下渗透本构关系。.研究结果揭示了岩石热冲击破裂过程中传热、细观破裂、宏观力学性质三者间的相关规律，为干热岩开发钻井与人工热储建造提供了技术支持和设计参数，拓宽了岩石力学内涵，丰富和发展了高温岩石力学理论。