SUGIMOTO Fumio AKITA UNIV., MINING COLLEGE,ASSOCIATE PROF., 鉱山学部, 助教授 (80124585)
IMAI Tadao AKITA UNIV., MINING COLLEGE,INSTRUCTOR, 鉱山学部, 助手 (00250895)
|Budget Amount *help
¥5,000,000 (Direct Cost : ¥5,000,000)
Fiscal Year 1997 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1996 : ¥3,500,000 (Direct Cost : ¥3,500,000)
Recently, much attention has been paid to the utilization of underground to build the repository for nuclear waste, the underground power house, the facilities for storage of oil, water, air and food, and so on. In the construction, maintenance and management of these structures, it has become important to evaluate the long-term stability of rockmass.
In this study, to clarify the failure phenomenon and machanism of creep in rocks, a series of uniaxial compression tests, uniaxial creep tests and the microscopic observations was carried out.
Creep tests were done for KIMACHI sandstone, AKIYOSHI marble, OGINO tuff and KURIHASHI granodiorite. Judging from the results of creep tests, secondary region in creep curve, which is divided into 3 regions, is subdivided into 2 regions according to the behavior of axial strain rate. The subdivided former region is characterized by the decrease of axial strain rate, and the latter one is by the increase of it.
The thin sections were made from the rock
specimens loaded until some compressive stress level and observed by the microscope. From the microscopic observations, it was found that the agent for detecting the cracks and pores in rocks has to be selected so that it may be suitable for the fabric and texture of each rock. Then, from the microscopic observations of the thin sections of KURIHASHI granodiorite loaded under creep tests, it was recognized that the intracrystalline microcracks extend mainly, and the number of intercrystalline microcracks increases as creep proceeds.
Also, to investigate the relationship between the failure processes of uniaxial compression and uniaxial compressive creep, the uniaxial compression tests were done for the rock specimens after creep load is applied to them during some elapsed time or until a given creep region. From the results of these tests, it was found that the residual uniaxial compressive strengths of rock specimens don't change until the former secondary creep region, and are lower from the latter one with the passage of time. Less