Heshe is an experimental well site that was established for hydrogeological characterization related research and technology development. The spatial distribution of fractures near the site was characterized through results of outcrop investigations and in-situ hydrogeological tests. The hydraulic conductivity of dominant fracture sets are determined and the hydraulic conductivity tensor is obtained accordingly. Based on the results of fracture characterization and associated parameters determined, this study adopts the software embedded in the Groundwater Modelling System (GMS) to establish a three-dimensional anisotropic numerical model to simulate flow of ground water. In comparison with cross-hole pumping test, the numerical model is utilized to investigate the effect of fractures induced anisotropy on groundwater flow. Studies show that when the principal permeability direction is rotated 10 degrees clockwise with respect to Y-axis, both horizontal and vertical flow increase at a rate of 1.52 times.

1. Introduction:

Discrete Fractured Network (DFN) model is one of the methods describing the hydraulic characteristics of fractured rock mass. DFN considers the hydraulic characteristic of anisotropy and heterogeneity with conductivity tensor according to the geometric characteristics of fractured distribution. Heshe well site in central Taiwan (Fig. 1) is established for hydrogeological characterization related research and technology development. Fig. 2 illustrates the layout of cross-hole pumping well within the site. Wang et al. (2015) characterized the geometric features of fractures and hydraulic parameters and Zhan et al. (2016) monitored groundwater flow via in-situ pumping test and bulit a hydrogeological Representative Volume Element (RVE) accordingly. Referred to the results of site characterization on Heshe well site, this manuscript establishes a numerical model to simulate ground water flow during in-situ cross-hole pumping test. The spatial distribution of dominate flow path is obtained by numerical simulation with proper equivalent parameters of hydraulic conductivity. The influences when the main direction of transmissibility changes, and its effect on the characteristics of ground water flow were also discussed.

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