Changes of permeability characteristics dependent on damage process in granites

摘要

Fracture properties are closely related to the permeability characteristics of massive crystalline rocks. In order to understand the changes of rock permeability related to the damage process, this study performed characterization on changes of hydraulic properties with both in-situ tests and laboratory tests. The results of in-situ tests showed that permeability coefficients have differences on each section from the distance of tunnel wall. The differences are related to the conditions of fracture distribution due to rock damage in the process of tunneling. This study performed uniaxial compressive tests (UCT) and water injection tests in order to understand the relationship between the damage process and changes of permeability characteristics by the laboratory tests. Crack distribution on each damage grade was observed by the acetate peel. According to the results of the tests, the strongly damaged specimens with crack length density of more than 0.6 cm−1 showed higher values of permeability coefficients than the weakly damaged specimens. Moreover, the former specimens have persistent cracks and good connectivity throughout the rock specimens. It indicates that rock damage influences on the permeability characteristics in rocks.