HR: 0800h
AN: T11A-0357    [Abstracts]
TI: Changes in permeability of fractured rocks by principal stress axes rotation
AU: * Takemura, T
EM: takato-takemura@aist.go.jp
AU: Takahashi, M
EM: takahashi-gonsuke@aist.go.jp
AB: The use of underground facilities such as waste reservoirs and power station caverns is increasing. Excavation of such spaces results in a change in stress distribution by principal stress axes rotation. Such changes alter the mechanical properties of rock mass such as strength and deformability, and the hydraulic conductivities and hence influence contaminant pathways. The stress redistribution is caused by excavation disturbed zone (EDZ) and rotation of tectonic stress. When the high-level nuclaer waste isolate long term, we have to consider changes in permeability by principal stress axes rotation. In this study, true tri-axial compresshon test was carried out under various stress conditions. The tested rock is damaged sedimentary rock, and has many fractures. Samples are loaded up to following conditions. Case1) isotropic stress condition, case 2) extension stress condition (maximum principal stress is equal to intermediate Principal Stress), and case 3) compression stress condition (intermediate Principal Stress is equal to minimum principal stress). After reached setting stress condition, permeability was measured under 0.05MPa pore pressure. As a result, permeability is the twice different by the change of the direction of principal stress even if mean stress is the same. The direction of fracture and principal stress axes are important factor to estimate long term stability of hydro-mechanical properties of fractured rock mass. This research project has been conducted under the research contract with the Japan Nuclear Energy Safety Organization (JNES).
DE: 1832 Groundwater transport
DE: 8168 Stresses: general
SC: Tectonophysics [T]
MN: 2007 Fall Meeting