(1. School of Resources and Environment Engineering，Jiangxi University of Science and Technology，Ganzhou，Jiangxi 341000，China；2. Key Laboratory of Mining Engineering of Jiangxi Province，Jiangxi University of Science and Technology，Ganzhou，Jiangxi 341000，China；3. Deep Vein Group Mine Intelligent Mining Technology Innovation Center of Ganzhou，Jiangxi University of Science and Technology，Ganzhou，Jiangxi 341000，China；4. School of Earth Science and Engineering，Sun Yat-Sen University，Zhuhai，Guangdong 519082，China；5. School of Resources and Earth Science，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China)
Abstract：Exploring the evolution of pore structure inside rocks under high-temperature cycles and its influence on physical and mechanical properties is essential for long-term stability analysis of underground engineering，such as geological disposal of nuclear waste and geothermal development. In order to quantitatively analyze the effects of high-temperature cycling on the pore structure and physical and mechanical properties of granite，the evolution of surface characteristics，mass，volume，P-wave velocity，tensile strength，porosity，pore size distribution，and microstructure of granite under high-temperature cycling from 25 ℃ to 800 ℃ were investigated by a combination of nuclear magnetic resonance(NMR)，scanning electron microscopy(SEM) and thermogravimetric-differential thermal analysis(TG-DTA). The results show that：(1) With the increase of the temperature，the surface cracks，color difference，mass loss rate(Rm)，volume expansion rate (RV)，P-wave velocity attenuation rate(RP) of granite keep increasing，the tensile strength(σt) gradually decreases，and the physical and mechanical parameters of granite change significantly when T＞500 ℃. After five thermal cycles，the variations of physical and mechanical parameters of the rock are more prominent. (2) High temperature can promote the development of granite pores，and micropores and smallpores inside the rock gradually grow and connect to form mesopores and macropores，resulting in the enhancement of rock pore connectivity. Thermal cycling will further increase the connectivity between pore structures，leading to an increase in the proportion of mesopores and macropores and a further increase in porosity. (3) The deterioration of granite's physical and mechanical properties under high-temperature cycling is closely related to the changes in its internal pore structure. The Rm and RV increase linearly with the increase of the equivalent average radius of the pore(rT)，and the RP and σt increase exponentially with the increase of rT. (4) High-temperature granite will be water evaporation，quartz phase transformation，mineral oxidation，chemical bond fracture and other physicochemical reactions，resulting in intergranular cracks，transgranular cracks and peeling defects of mineral particles. Especially，the rock structure damage is more significant after quartz phase transformation at 573 ℃. (5) Thermal cycling will cause fatigue damage to the rock，and the alternating thermal stress generated by high-temperature cycling promotes the increase and expansion of microcracks，resulting in increased granite damage.
古启雄1，2，黄 震1，2，钟 文1，2，3，李仕杰4，吴 云5，巫宇帆1，2. 高温循环后花岗岩孔隙结构与物理力学特性演化规律研究[J]. 岩石力学与工程学报, 2023, 42(6): 1450-1465.
GU Qixiong1，2，HUANG Zhen1，2，ZHONG Wen1，2，3，LI Shijie4，WU Yun5，WU Yufan1，2. Study on the variations of pore structure and physico-mechanical properties of granite after high temperature cycling. , 2023, 42(6): 1450-1465.
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2023, Vol. 42 
