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以高放废物重点预选场址甘肃北山花岗岩为研究对象,开展了不同温度和不同加热速率高温损伤后岩石压缩全过程渗透率试验。研究发现:(1)饱水率、波速、弹模、峰值强度等物理力学性质及渗透率突变温度阈值均在500℃~600℃之间;低于500℃处理后试件的初始渗透率无明显变化,600℃处理后,晶内裂纹的大量出现使裂纹连成网络,岩石的初始渗透率急剧增长,增长幅度达2~3个量级。(2)低于5℃/min,岩石的损伤主要由造岩矿物颗粒热膨胀系数和弹性模量的不同导致在颗粒间形成热应力造成的;高于5℃/min,温度梯度导致的热应力将诱发裂纹。(3)电镜扫描显微图像显示100℃~573℃处理后裂纹主要集中在晶粒边界,高于573℃处理后长石和石英晶体内相继出现穿晶裂纹,晶内破裂均贯通整个晶粒,与周围裂隙网络连接。(4)热处理后试件渗透率出现2种不同的渗透类型:600℃以下处理后试件在压缩全过程随应力增加渗透率分为下降段、水平段、稳定增长段和急剧上升段;600℃以上高温处理后,渗透率在压缩全过程持续降低。(5)弹性阶段前渗透率与裂隙体积应变呈现良好的线性关系,随裂隙体积的减小,渗透率降低。
Taking the Beishan granite in Gansu Province as the pre-selected site for high-level radioactive waste as the research object, the permeability tests of the whole process of rock compression after high temperature damage at different temperatures and different heating rates were carried out. The results show that: (1) The thresholds of physical and mechanical properties, such as water saturation, wave velocity, elastic modulus and peak intensity, and the threshold of sudden change of permeability are both between 500 ℃ and 600 ℃; initial permeability of specimens below 500 ℃ Significant changes, after 600 ℃ treatment, a large number of intracrystalline cracks in the cracks connected into the network, the initial permeability of rock increased sharply, an increase of 2 to 3 orders of magnitude. (2) Below 5 ℃ / min, the damage of rock is mainly caused by the thermal stress between the particles caused by the difference between the thermal expansion coefficient and the elastic modulus of the granite. If the temperature is higher than 5 ℃ / min, the thermal stress caused by the temperature gradient Cracking will be induced. (3) Scanning electron microscopy (SEM) images show that the cracks mainly focus on the grain boundaries after the treatment at 100 ℃ ~ 573 ℃, and the transgranular cracks successively appear in the feldspar and quartz crystal after the temperature is higher than 573 ℃. Connect with surrounding crack network. (4) There are two different infiltration types of specimens after heat treatment: the samples with the temperature below 600 ℃ are divided into descending section, horizontal section, stable growth section and sharp rising section with increasing stress in the whole process of compression. ℃ above the high temperature treatment, the permeability of the compression process continued to decline. (5) There is a good linear relationship between permeability and fracture volumetric strain before the elastic phase. As the volume of fracture decreases, the permeability decreases.