温度影响下花岗岩宏、细观力学性质演化规律

在地下工程中，温度变化对岩体力学性质有着极大的影响，而宏观力学性质与细观微裂隙发育损伤密不可分。为探究在温度循环条件下岩石细观损伤机理与宏观力学性质之间的关系，对花岗岩进行不同温度下的高温水冷循环试验，并采用低场核磁系统进行细观孔隙参数检测，同时开展了单轴抗压强度试验。结果表明：（1）温度的上升和循环次数的增加均会导致花岗岩弹性模量和单轴抗压强度力学性质的降低，400 ℃是花岗岩性质变化的临界点；（2）核磁检测可以获取试件的孔隙分布参数，由该参数及试件宏观性质变化可以得出，200~600 ℃时温度循环所引起的细观损伤规律有明显差异；（3）花岗岩损伤值随着温度的升高而升高，但温度循环引起的多次损伤随温度的升高呈现出先增加后减小的趋势。微裂隙尺度、含量与试件单轴强度、应变的相关性分别为-0.943和0.935。

Evolution of Macro and Meso Mechanical Properties of Granite Under the Influence of Temperature

In many underground engineering construction，the temperature change has a great impact on the macro mechanical properties of rock mass.The macro mechanical properties of the rock mass are closely related to the development and damage of micro cracks.In order to explore the relationship between meso damage mechanism and macro mechanical properties under the condition of temperature cycling，the granite was tested with different cold and heat cycles under five temperature conditions of 200，300，400，500 and 600 ℃，and then the micro pore parameters were detected by low field NMR（nuclear magnetic resonance） system.The macro uniaxial compressive strength of granite specimens under different temperature conditions was tested by universal hydraulic testing machine.Finally，through the fitting analysis of macro mechanical properties and damage parameters，as well as the correlation detection and analysis of meso parameters and macro parameters，the evolution relationship between micro pore fracture parameters and mechanical properties of granite under the condition of temperature cycle was studied.The results show that：（1）The increase of temperature and the number of cold and hot cycles will lead to the decrease of mechanical properties such as elastic modulus and uniaxial strength of granite，and the influence of cold and hot cycles on the decrease of rock strength after 400 ℃ is more obvious.（2）Nuclear magnetic testing can effectively obtain the pore distribution parameters of specimens under different temperatures.Combined with the changes of meso parameters and macro properties，it can be concluded that when the temperature is below 400 ℃，the micro cracks and damage formed in the rock are mainly caused by factors such as water overflow and internal stress concentration，while when the temperature is higher than 400 ℃，the micro cracks are mainly formed by mineral crystal creep and crystal denaturation，and at this time，a large-scale fracture group will be formed.（3）The damage value of granite increases with the increase of temperature，but the multiple damage caused by cold thermal cycle increases first and then decreases with the increase of temperature.The correlation parameter between the size of micro cracks in granite and the uniaxial compressive strength of the specimen is -0.943，and the correlation parameter between the content of micro cracks and the strain of the specimen is 0.935.