Three-Dimensional Detection Technology on the Network-Like Permeability Structure of Granitic Rock Mass

甘肃北山作为高放废物地质处置库场址预选区，其围岩渗透结构类型是研究岩体渗透性和核素在裂隙通道中迁移路径的重要内容。根据岩体结构面级别划分理论为基础，结合甘肃北山高放处置库围岩不同尺度地质结构面工程意义，分为2大类5小级：一大类为断裂带，I级结构面为区域断裂(数十公里级)，II级结构面为边界断裂(公里级)；二大类为节理裂隙，III、IV级结构面为长大裂隙与小断层(数十米~数百米级)，V级结构面为处置孔周围微裂隙与节理(厘米~米级)。其中，根据岩体的宏观渗透特征，甘肃北山围岩结构面主要以网络状渗透结构存在。结合现场地形条件，运用电阻成像技术对岩体网络状三维渗透结构进行探测，通过测线布置、数据采集、解编处理，反演岩体全空间电阻率，可视化地呈现了裂隙岩体渗透结构在压水试验下的渗透路径及变化范围。结果表明，电阻层析成像探测结果与压水试验渗水量相吻合，表明地球物理勘探方法可以运用于花岗岩体渗透结构探测。As a preselected area of geological disposal site of high-level radioactive waste in Beishan, Gansu province, the type of surrounding rock permeability structure is an important content to study the permeability of rock mass and the migration path of nuclides in the fracture channel. Based on the classification theory of rock mass structural plane and the engineering significance of geological structural plane of different scales in the surrounding rocks, it is divided into two categories and five grades. The structural planes of grade III and IV are large cracks and small faults (tens of meters to hundreds of meters), and the structural planes of grade V are micro-cracks and joints around the disposal hole (centimeters to meters). According to the macroscopic seepage characteristics of rock mass, five types I~V of rock permeability structure i preselected area are granular, interlayered, banded, network-like and pipe-like permeability structure. Combined with the topographic conditions of the site, electrical resistivity technology was used to detect the permeability structure of the rock mass. Three-dimensional resistivity data of the rock mass was inversed through the data collection, compilation processing, and the permeability path and variation range of the fractured rock mass permeability structure were visualized. Through the compared results of electrical resistivity tomography and packer permeability test, it indicates that the geophysical exploration method can be used to detect the permeability structure types of multiple-scales structural plane of granitic rock mass.