变幅冷却循环花岗岩单轴压缩强度及变形破坏演化规律  

Uniaxial compressive strength and deformation failure evolution of granite treated by cooling cycles with variable temperatures

作　　者：辛光明 郑勇 党金铭 王绪奎 沈建波 于海峰 李猛 闵祺 XIN Guangming;ZHENG Yong;DANG Jinming;WANG Xukui;SHEN Jianbo;YU Haifeng;LI Meng;MIN Qi(Jining Energy Development Group Co.,Ltd.,Jining 272000,China;College of Energy and Mining Engineering,Shandong University of Science and Technology,Qingdao 266590,China)

机构地区：[1]济宁能源发展集团有限公司,山东济宁272000 [2]山东科技大学能源与矿业工程学院,山东青岛266590

出　　处：《西安科技大学学报》2022年第5期902-908,共7页Journal of Xi’an University of Science and Technology

基　　金：国家自然科学基金项目(51974173,52004147);山东省自然科学基金项目(ZR2020QE129)。

摘　　要：增强地热系统(EGS)在储层激发及热能回采过程中经常遇到变温冷却循环现象,该现象加快了干热岩局部破损,极易导致地热储层出现漏失及储热效果降低等问题。为研究变温冷却循环处理花岗岩力学性能及破坏特征演化规律,借助岛津岩石力学试验机开展了变温冷却循环处理花岗岩的单轴压缩试验,结果表明:花岗岩单轴抗压强度随循环次数增加而降低,当循环增至12次时,温度降低幅度分别为10,15及20℃条件下的单轴抗压强度分别降低了18.63%,7.04%及5.16%;但随温度降低幅度增加而增加,随温度降低幅度由10℃增至20℃,循环4,8及12次条件下的花岗岩单轴抗压强度分别增加了12.00%,22.40%及30.54%。花岗岩破坏产生的累积声发射能量随循环次数增加而减少,但随温度降低幅度增加而增加。变温冷却循环处理花岗岩破坏以拉剪混合及张拉破坏2种模式为主。随循环次数增加或温度降低幅度减少,花岗岩破坏模式由拉剪向张拉破坏转变,破坏时的剥落面积增加,整体裂纹数量减少。Enhanced geothermal system often encounters the phenomenon of cooling cycles with variable temperature in the process of reservoir excitation and thermal energy mining, which accelerates the local damage of hot dry rock and easily results in the leakage of geothermal reservoirs and the decrease of heat storage effect.In order to study the evolution law of mechanical properties and failure characteristics of granites treated by cooling cycles with different variable temperatures, the uniaxial compressive test of granites were conducted through the rock mechanics testing machine.The results showed that: the uniaxial compressive strength of granites is decreasing with the increase of cycles, and when the cycle is increased to 12 times, the uniaxial compressive strength decreases by 18.63%,7.04% and 5.16% at the temperatures reduction of 10,15 and 20 ℃,respectively.However, the uniaxial compressive strength is increasing with the increase of temperature reduction amplitude, and when the amplitude is increasing from 10 ℃ to 20 ℃,the uniaxial compressive strength of granites increases by 12.00%,22.40% and 30.54% after 4,8 and 12 cycles, respectively.The cumulative acoustic emission energy of granites failure decreases with the increase of cycle times, but increases with the increase of temperature reduction amplitude.The failure modes of granite treated by cooling cycles are mainly tension-shear mixed and tensile failure.With the increase of cycle times or the decrease of temperature reduction amplitude, the failure modes of granites change from tension-shear mixed failure to tensile failure, the spalling area increases, but the overall number of fractures is reduced.

关 键 词：温度降低幅度 冷却循环 峰值强度 宏观破坏 剥落面积 

分 类 号：P314[天文地球—固体地球物理学]