摘要:
随着能源的需求日益增加，高温岩体工程如矿产资源深度开采、地热资源开发、高放核废料地下深埋处置、CO2地质封存固化等得到了进一步发展，因而需要准确分析高温和高压条件对储层岩石物理力学变化机制。基于此，通过对高温后（20~600℃）的花岗岩进行不同围压作用下的常规三轴压缩试验，分析了不同围压下高温后花岗岩试样常规三轴压缩全应力-应变关系，探讨了温度、围压对花岗岩的强度和变形特征及破坏形式的影响，同时结合高温后花岗岩偏光显微镜图像，从微观上揭示了高温后花岗岩力学特征变化的机制。研究结果表明：（1）高温对花岗岩体积应变的膨胀有很大影响，温度越高，试样体积膨胀的越明显，高温后花岗岩三轴抗压强度和弹性模量皆随温度的升高而逐渐降低，随围压的升高而增大，且高温后花岗岩粘聚力和内摩擦角皆随温度的升高而降低；（2）温度大于400℃时，花岗岩强度和变形参数降低幅度呈现突然增大的趋势，且微观裂纹的密度和平均宽度总体上也有突然增大的趋势，单轴压缩条件下破坏形态也由轴向劈裂破坏向剪切破坏过渡，花岗岩强度和变形参数及破坏形式变化的阈值温度应大于400℃；（3）结合偏光显微镜图像观测结果，发现随着温度的升高，岩石内部水分子逸出、矿物晶体膨胀系数的差异及矿物晶体物理变化导致花岗岩试样内部晶间和晶内微裂纹逐渐萌生、扩展和交汇成裂纹网络，导致高温后花岗岩力学特性的变化。研究结果希望为高温的岩体工程开发的相关计算与数值模拟提供理论依据。
Abstract:
With the increasing demand for energy, high-temperature rock engineering such as the mining of deep underground solid mineral resources, geothermal energy extraction, deep nuclear waste repositories, and CO2 geological storage and solidification have been further developed. Therefore, it is necessary to accurately analyze the influence of high temperature and high pressure on the changing mechanisms of physical and mechanical properties of reservoir rocks. Based on the conventional triaxial compression tests of granite after high temperature ranging from 20 to 600℃ under different confining pressures, complete stress-stain curves of granite heated to various temperatures under conventional triaxial compression are analyzed and the influence of temperature and pressure on the deformation and strength characteristic and failure mode is discussed. Meanwhile, the mechanical changing mechanism of granite after exposure to various temperatures is revealed by optical microscopy observations. The test results show that: (1) Temperature has a significant effect on the expansion of volumetric strain, and the higher the temperature, the more obvious the volume expansion of the specimens. The triaxial compressive strength and elastic modulus of granite after high temperature gradually decrease with temperature, and increase with confining pressure. The cohesion and internal friction angle of granite after high temperature both decrease with temperature; (2) When the temperature is higher than 400℃, the changes in strength and deformation parameters of granite greatly increases, and the density and average width of microcracks also present a sudden increase trend overall. Meanwhile, the failure mode of the specimens under uniaxial compression condition changes from axial splitting failure to shear failure. The threshold temperature for the strength and deformation parameters and failure mode of granite is higher than 400℃; (3) Based on polarization microscopy observations, it was found that the escape of water molecules inside rock bodies, differences in mineral crystal expansion coefficients and mineral chemical changes lead to the initiation, propagation and interaction of microcracks between and within crystals in the granite, which ultimately causes the changes in the mechanical properties of the granite after exposure to various temperatures. The experimental results in this study is hoped to provide a theoretical basis for the design calculations and numerical simulations of high-temperature rock engineering projects.
百度学术
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