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目的:研究高温热开裂后红砂岩的物理力学性能和渗透性的量化变化规律。创新点:1.相比于传统液体稳态流渗透率测试法耗时多的缺点,本文通过氮气渗透方式,可快速获得低渗透率岩样的稳态流渗透率;2.从裂隙体积变化角度,分析不同温度热开裂红砂岩在三轴压缩条件下的各裂隙发展阶段,讨论其与渗透性演化的关系。方法:1.通过纵波波速测试和带渗透性实时监测的三轴压缩试验等手段,获得热处理后红纱岩基本物理力学性质参数(表1和表2)、不同围压下的全应力-应变关系曲线、轴向应变-体变关系曲线以及渗透率变化曲线(图4和图8);2.通过理论分析和计算,获得轴向应变与裂隙体变的关系曲线(图9),分析裂隙演化5个阶段中渗透率的演化规律。结论:1.由20到200°C,红砂岩原生孔隙和裂隙发生闭合,增加了试样密实度,并引起强度和弹模的提高以及初始渗透率的降低;从200到600°C,红砂岩内部结构逐渐劣化,导致强度和弹模降低,峰值应变和初始渗透率提高;2.加载过程中试样渗透率随裂隙的演化而变化,裂隙演化可分为压密、线弹性变形、裂隙稳定发展、宏观剪切破坏和应变软化5个阶段。这5个阶段中渗透率变化趋势不同;3.当受热温度继续增大至800°C时,红砂岩出现严重的裂纹致使其破坏。
Objective: To study the quantitative changes of physical and mechanical properties and permeability of red sandstone after thermal cracking. Innovative points: 1.Compared with the shortcomings of the traditional liquid steady state flow rate test method, this paper can quickly obtain the steady state permeability of low permeability rock samples by nitrogen infiltration method.2. From the change of fracture volume From the angle of view, the development stages of fractures of red-sandstone with different temperature under triaxial compression were analyzed, and the relationship between permeability and permeability evolution was discussed. Methods: 1. The basic physico-mechanical properties parameters (Table 1 and Table 2) of red veil after heat treatment were obtained by means of longitudinal wave velocity test and triaxial compression test with permeability real-time monitoring. The total stress- (Figure 4 and Figure 8); 2. Through the theoretical analysis and calculation, the relationship between the axial strain and the deformation of the fissure was obtained (Figure 9), and the fissure was analyzed Evolution of permeability in five stages of evolution. Conclusions: 1. From 20 to 200 ° C, the primary pores and fractures of red sandstone are closed, increasing the compactness of the sample and causing the increase of the strength and the elastic modulus and the decrease of the initial permeability; from 200 to 600 ° C, the red The internal structure of sandstone gradually deteriorates, which leads to the decrease of strength and modulus, the increase of peak strain and initial permeability. 2. The permeability of specimens changes with the evolution of cracks during loading. The evolution of fractures can be divided into compaction, linear elastic deformation, Stable development, macroscopic shear failure and strain softening five stages. The trend of permeability changes in these five stages is different; 3.When the heating temperature continues to increase to 800 ° C, severe damage to red sandstone causes it to rupture.