The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement and groundwater flow conditions have been altered due to the excavation itself. In this study, the ‘hydraulic EDZ’ is defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation. And hydraulic EDZ (hydraulic aperture changed zone) estimated using two-dimensional DEM program was considered in a threedimensional DFN model. Using this approach, the groundwater flow characteristics corresponding to hydraulic aperture change were examined. Together, a parametric study was performed to examine the boundary conditions that are frequently used in DFN analysis, such as constant head or constant flux conditions. According to the numerical analysis, the hydraulic aperture change induced by the hydraulic-mechanical interaction becomes one of the most important factors influencing the hydraulic behavior of jointed rock masses. According to the results of this study, we suggest the proper boundary condition using a three-dimensional DFN model.
The excavation damaged zone (EDZ) is generally defined as the zone beyond the excavation boundary where the rock has been significantly disturbed and/or damaged due to the excavation and re-distribution of stresses [1]. Various studies have investigated EDZ [2, 3], with most studies focusing on the mechanical behavior of EDZ using in situ experiments. Even though the EDZ could potentially form a highly permeable pathway for groundwater flow, only a few studies have analyzed groundwater flow in EDZs. Therefore, we investigate the characteristics of hydraulic aperture changes due to stress re-distribution. We define a ‘hydraulic excavation damaged zone (H-EDZ)’, the zone adjacent to the excavation where the hydraulic aperture has been changed due to excavation. In order to investigate the influence of the hydraulic aperture change, we have employed a numerical analysis using a discrete fracture network (DFN) which can simulate groundwater flow through three-dimensional discrete fractures. DFN approach is widely used in flow monitoring to evaluate the groundwater flow. In the DFN model, however, fracture aperture does not change as time and stress re-distribution after excavation. In view of this, we recently completed a numerical analysis that investigated the behavior of the hydraulic aperture near the cavern for different stress ratios, initial apertures, fracture angles and fracture spacing using a twodimensional distinct element method (DEM) program [4]. Accordingly, H-EDZ was considered in a three-dimensional DFN model in this paper.
The hydraulic aperture changed zone (H-EDZ) near the excavated cavern was estimated using the two-dimensional distinct element method, with hydraulic-mechanical coupling analysis [4, 1152 5]. In the same groundwater level, the behavior of the hydraulic aperture near the cavern was analyzed for different stress ratios, initial apertures, fracture angles and fracture spacing. Typical results of this coupled analysis are shown in Figure 1. As seen in Figure 1, the hydraulic aperture changed zone induced by the hydraulic-mechanical interaction is the shape of an ellipse and is perpendicular to the fracture direction.
