Influence of rate of change in stress field to the fracture phenomena

Research Project

Project/Area Number	60550445
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	資源開発工学
Research Institution	Yamaguchi University
Principal Investigator	OGINO Shoji Yamaguchi University, Professor, 工学部, 教授 (90035014)
Co-Investigator(Kenkyū-buntansha)	SANO Osam Yamaguchi University, Research assistant, 工学部・資源工学科, 助手 (20127765) MIZUTA Yoshiaki Yamaguchi University, Assistant Professor, 工学部・資源工学科, 助教授 (20107733)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥1,600,000 (Direct Cost: ¥1,600,000) Fiscal Year 1986: ¥200,000 (Direct Cost: ¥200,000) Fiscal Year 1985: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywords	triaxial test / confining pressure / strain rate
Research Abstract	In the mechanical testing of metals, the applied stress is usually uniaxial. However, for rocks, three principal stresses are commonly non zero, because the triaxial stress state can effectively simulate overburden stress. The usual triaxial tests are carried out by stressing the rock under confining pressure. However, in most practical situations, the fracture of the rock occurs due to a creation of the free surfaces such as an under-ground openings. Then the maximum stress (tensile stress is taken to be positive) should be decreased. In this research, we introduce an new experimental procedure, depressing test. The new test start from the hydrostatic stress state, where the axial strain rate is kept constant. The confining pressure is decreased at various depressing rate simultaneously. Rock specimens fractured violently, while in usual confined test rock specimen behave ductile under relatively high confining pressure.