Abstract

Permeability is the key factor to control long-term stability of surrounding rock of high level radioactive waste (HLW) geological repository. In view of the low permeability of the intact granite in Beishan area, the preferred site for HLW repository in Northwest China, argon was used as the fluid medium to measure the gas permeability of Beishan granite under hydrostatic pressures and cyclic loading-unloading triaxial tests. It is found that the gas permeability decreases with the increase of confining pressure and their relationship approximately conforms to the power function. Due to irreversible plastic deformation, the permeability during unloading is less than that in loading process under the same confining pressure level. In the triaxial loading-unloading test, the acoustic emission technique applied well reflects the micro-crack propagation process and quantifies the cumulative damage in granite samples. It shows that the dilatancy stress is the threshold stress of the micro cracks in rock turn from stable growth to accelerated growth. This is the physical mechanism of significant increase of permeability after reaching the dilatancy stress.

摘要

渗透率是控制高放废物地质处置库围岩长期稳定性的关键因素。【摘要】：针对我国西北地区高放废物处置库首选地北山地区完整花岗岩的低渗透性,以氩气为流体介质,在静水压力和循环加卸载三轴试验条件下,对北山花岗岩的气体渗透率进行了测量。发现气体渗透率随围压的增加而降低，其关系近似服从幂函数。由于不可逆塑性变形，在相同围压水平下，卸载过程中的渗透率小于加载过程中的渗透率。在三轴加卸载试验中，应用的声发射技术很好地反映了微裂纹扩展过程并量化了花岗岩样品的累积损伤。表明剪胀应力是岩石微裂纹从稳定扩展到加速扩展的阈值应力。这就是达到剪胀应力后渗透率显着增加的物理机制。