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投稿时间：2021-06-27 修订日期：2022-03-24
投稿时间：2021-06-27 修订日期：2022-03-24
中文摘要: 深部岩土工程常常面临复杂的变温环境，研究岩石力学特性热循环效应对于评估储层与围岩稳定性及合理利用岩石材料至关重要。对于细粒致密花岗岩地热储层，其力学特性关系到能源高效开采及工程安全问题。因此，本文对花岗岩试样开展了热循环试验、单轴压缩试验和光学显微镜观测试验，以研究其破坏特征、力学参数变化，以及细粒致密结构对花岗岩力学特性影响机制。结果表明：岩石的破坏特征与力学性质随着热循环温度和次数的变化趋势与其结构紧密相关，热循环上限温度升高能够提高花岗岩力学性质随着热循环劣化的敏感性。对于细粒致密结构的花岗岩，其单轴抗压强度与弹性模量随着热循环上限温度和循环次数增加而逐渐降低；热循环次数超过10以后，单轴抗压强度降低速率变得缓慢；300 ℃以内热循环不会改变细粒致密花岗岩脆性破坏特征。通过显微观测分析表明，热循环能显著促进花岗岩裂纹扩展，在从室温（20 ℃）到上限温度300 ℃热循环20次后，其线性裂纹密度为1.69 mm–1，是热循环1次时的1.5倍；由于结构细粒致密，约束了花岗岩矿物颗粒的膨胀压密效应，造成热应力诱发的裂纹萌生与扩展演化作用占据优势，进而宏观力学参数随着相应线性裂纹密度呈现非线性降低。研究对于变温环境下深部岩土工程力学问题相关探索具有一定基础参考价值。
Abstract:Deep geotechnical engineering often faces complex variable temperature environments. The thermal cycle effect of rock mechanical properties is important for the stability evaluation of reservoir and surrounding rock and the rational utilization of rock materials. For fine grained dense granite geothermal reservoir, its mechanical properties are related to energy-efficient exploitation and engineering safety. Therefore, thermal cycling experiment, uniaxial compression experiment, and optical microscope observation experiment were carried out to study the failure characteristics, the changes in mechanical parameters, and the influence mechanism of fine grained dense structure on the mechanical properties of granite. The results showed that the changing trend of rock failure characteristics and mechanical properties with the temperature and times of thermal cycle was closely related to the structure. For the fine grained dense granite, the uniaxial compressive strength and elastic modulus gradually decreased with the increase of upper limit temperature and times of thermal cycle, and the reduction rate of compressive strength became slow after more than 10 thermal cycles. The increase of the upper limit temperature of the thermal cycle can improve the sensitivity of the mechanical properties of granite to the deterioration of the thermal cycle. Internal thermal cycling at 300 ℃ would not change the brittle failure characteristics of fine grained dense granite. The microscopic observation and analysis show that the thermal cycle could significantly promote the crack propagation of granite. After 20 thermal cycles at 20～300 ℃, the linear crack density was 1.69 mm–1, which was 1.5 times that of one thermal cycle. Due to the fine and dense structure, the expansion and compaction effect of granite mineral particles was constrained, resulting in the predominance of crack initiation and propagation evolution induced by thermal stress, and then the macro mechanical parameters decreased nonlinearly with the corresponding linear crack density. This study had a certain reference value for the exploration of deep geotechnical engineering mechanics problems in variable temperature environments.
keywords: deep rock mechanics fine grained dense granite geothermal development microcrack thermal cycle
文章编号：202100605 中图分类号：TU45 文献标志码：
基金项目:国家重点研发计划项目（2018YFC0808401）；深地科学与工程教育部重点实验室开放基金（DESE202104）；中国博士后科学基金面上项目（2020M673225）；中央高校基本科研业务费资助（2021SCU12039）
作者简介:第一作者：张建国（1963—），男，教授级高级工程师，博士. 研究方向：岩土工程. E-mail：zhangjg_z@126.com;通信作者：冯淦, E-mail：fenggan@scu.edu.cn
引用文本：
张建国,冯淦,王晓川,康勇.热循环影响的细粒致密花岗岩力学特性试验[J].工程科学与技术,2022,54(5):19-28.
ZHANG Jianguo,FENG Gan,WANG Xiaochuan,KANG Yong.Mechanical Properties of Fine Grained Dense Granite Affected by Thermal Cycles[J].Advanced Engineering Sciences,2022,54(5):19-28.
引用文本：
张建国,冯淦,王晓川,康勇.热循环影响的细粒致密花岗岩力学特性试验[J].工程科学与技术,2022,54(5):19-28.
ZHANG Jianguo,FENG Gan,WANG Xiaochuan,KANG Yong.Mechanical Properties of Fine Grained Dense Granite Affected by Thermal Cycles[J].Advanced Engineering Sciences,2022,54(5):19-28.