Abstract
The cross-hole test is useful for evaluating the channel system developing in a fractured rock mass. The pressure responses observed in a series of cross-hole test that is carried out at a dam site were analyzed. The rock of the site was mainly composed of the mixture of weathered granite and gneiss and had many fractures in it. Some channels of high permeability are existing in this weathered fractured rock mass. Also, some major fractures that are filled with fault clay have low permeability and act as the barrier interrupting groundwater flow. The patterns of the pressure response observed in the test were divided into 5 types. These types are closely related to the geometry of channels with high permeability and barriers existing in the rock mass. The effect of those channels and barriers on the pressure response are analyzed by using an idealized channel network model.
