ABSTRACT:

Permeability is one of the main factors of groundwater flow. The change in permeability has been a great influence in the change in mechanical loading in such operations as underground excavation. Therefore, an analysis of the relationship between permeability and stress is of great concern. The influence of the mechanical loading on the change in permeability was studied on the hollow cylindrical samples of Pocheon Granite produced in Korea subjected to repeated uniaxial loading. Measurements were taken firstly in the linear portion of the stress-strain curve, secondly in the strain-hardening region near the peak stress, and finally in the strain-softening region after macroscopic fractures had formed. Also, modeling of the relationship between lateral permeability and mechanical loading was performed under the uniaxial compressive stress condition using crack models considering rock matrix permeability. The lateral permeability data of the models were not exactly the same as that of the tests, but the general values and patterns were reasonable to simulate the actual permeability data. In particular, patterns of lateral permeability were very similar to the test results in nonlinear portion.

INTRODUCTION

Demands of underground structures such as storage caverns and waste repositories have been increasing with study results on safe and efficient space utilization and with the rise of environmental issues. In relation with environmental, safety and operational issues like groundwater pollution, long-term stability etc., change in groundwater flow is of serious concern. The excavation of an underground structure will cause the development of cracks in a small scale and the stress redistribution around it in a large scale (Pusch, 1992). In addition, in the petroleum industry the connectivity of a fracture reservoir will change due to changes in mechanical loading. Mechanical loading can give rise to changes in the hydraulic characteristics of a rock mass.

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