The effect of fracture outcrops around tunnel on seepage

Parameters of fractures are the basic components of hydraulic models in fractured rocks. However, the outcrops of fractures on the hydraulic boundary are the actual passages of inflow and outflow in fractured rocks and tunnel wall. The computer code, TUNFLOW, which base on the discrete fracture model is applied to estimate the hydraulic conductivity and outcrops of simulated cases in this research. The results show that the preferential path exists in partial fracture net. Density and trace length of fractures are the major factors to amount of the effective outcrops, which are the outcrops that groundwater passed. There is a fairly relation between seepage and outcrops on the tunnel wall. This result could be used in estimating the groundwater surge with number of outcrops, and result in the case of Syueshan tunnel is very close to the record in-situ.