关键词: 甘肃北山, 断裂损伤带, 原状裂隙岩, 流动测试, 水力特性

Abstract: Hydraulic conductivity is one of the critical parameters for evaluating flow properties of water-bearing media. The variation of this parameter generally leads to uncertainties of ground water flow and solute transport in fractured rock masses, and furthermore influences justification of important issues involving migration and diffusion of high-level radioactive wastes (HLW) in hard-rock repository. In this paper, we mainly focus on the permeability of meso-scale fault zones in granitic rock mass, which belongs to Jiujing, one of the pre-selected areas for Chinese HLW repository in Gansu Beishan. We carry out fluid flow tests on the undisturbed fractured samples collected from one of these fault zones via non-standard test apparatus and obtain the variability of hydraulic conductivity. We then realize the identification of dominant flow paths by slicing the samples and extracting internal flow parameters using staining solution. The results illustrate that three sets of fractures can be identified within the fault zone (Shiyuejing fault). Hydraulic conductivities of the fractured samples with more set I fractures are mainly over 10?4 cm/s, while those of samples with more set II or III fractures are respectively in the range of 10?5-10?4 cm/s and lower than 10?5 cm/s, mostly 10?6-10?7 cm/s. Permeability of the three kinds of samples thus decreases successively. Three types of flow states, namely the laminar flow type (samples 4, 6, 10-12), the infilled type (samples 2, 7), and the erosive type (samples 1, 5, 8, 9, 13, 14), are indicated by the corresponding characteristics of P-Q (pressure-flux) curves. Permeability of these three types also successively drops.

Key words: Beishan of Gansu province, fault damage zone, undisturbed fractured rock, fluid flow test, hydraulic characteristics