Mechanical Behavior and Permeability of Simulated Rock with Single Fracture under Brittle and Ductile Conditions

Abstract

Gypsum aggregate specimens have been used in the present study, because brittle, semi-brittle and ductile stress-strain behaviors of the specimen can be controlled only with confining stress level at the room temperature. At confining stresses up to 40 MPa, tri-axial compression and fluid flow experiments have been conducted on the intact specimens and single fracture specimens. It has been indicated that stress-strain behavior is independent of existence of fracture. Moreover, permeability of the single fracture specimen is much higher than intact specimen at conditions of brittle, semi-brittle, intermediate state between semi-brittle and ductile and ductile condition. On the other hand, permeability of the single fracture specimen is not so different from that of the intact specimen at conditions of a transitional behavior between semi-brittle and ductile stress-strain behaviors. As for the geothermal reservoir in the semi-brittle and ductile region, it was suggested that the fracture is retained and permeability is maintained when fracturing occurs due to hydraulic crushing or the like.

Keywords

• gypsum
• brittle
• semi-brittle
• ductile
• mechanical characteristics
• hydraulic characteristics