The naturally existing fractures in a rock mass induce heterogeneity and anisotropy for its engineering properties, resulting in difficulties for investigation on hydrogeological characteristics of fractured rock masses. Aiming to gain more insight into the difference of permeability of distinct fracture sets in a rock mass and associated influence on the equivalent permeability of the rock mass, this study adopts statistical analyses to estimate the hydrogeological characteristics from a series of in-situ test results. There are 10 boreholes drilled within a radius of 9.2m in a wells site with more than 50 testing results for conductivities. The hydraulic conductivity obtained from distinct hydrogeological tests can differ several orders, depending on number of fractures, fractural set and fractural conditions comprised in the testing section. Furthermore, statistical analysis for the testing results determines the transmissivity for distinct fractural sets, which provides an alternative for relevant investigation of in-situ hydrogeological tests.
An appropriate hydrogeological model for a site investigation is essential for the simulation of ground water flow and solute transportation, and is also necessary for the evaluation of extractable ground water and further underground usage. As far as a fracture rock mass is concerned, groundwater always flows through fracture planes. The hydrogeological characteristics of such a rock dominate by the fractural network, geometry and infilling materials of the fractural plane, which hinder from detail investigations and precise estimation on the conductivity of a fracture rock.
Based on a wells site set up for in-situ hydrogeological investigation, this manuscript introduces the design consideration for well arrangement and related tests items and positions. The measured data are statistically analysis to determine the conductivity of the site and the transmissivity of each fracture set. Discussions regarding the factors affecting the transmissivity of fracture set are also provided.