1992 Fiscal Year Final Research Report Summary
Rock Stress Measurement by Hydraulic Fracturing with Hemispherical-ended Borehole
| Project/Area Number |
03452241
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
資源開発工学
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| Research Institution | Kumamoto University |
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Principal Investigator |
OKAMURA Hiroshi Kumamoto University, Faculty of Engineering, Professor., 工学部, 教授 (40040373)
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| Co-Investigator(Kenkyū-buntansha) |
KOIKE Katsuaki Kumamoto University, Faculty of Engineering, Associate Professor., 工学部, 助手 (80205294)
NAKAYAMA Tomoharu Kumamoto University, Faculty of Engineering, Associate Professor., 工学部, 助手 (70207950)
KANEKO Katsuhiko Kumamoto University, Faculty of Engineering, Associate Professor., 工学部, 助教授 (20128268)
OBARA Yuzo Kumamoto University, Faculty of Engineering, Associate Professor., 工学部, 助教授 (50135315)
SUGAWARA Katsuhiko Kumamoto University, Faculty of Engineering, Professor., 工学部, 教授 (60109668)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Rock Stress Measurement / Hydraulic Fracturing / Finite Element Method / Hemispherical-ended Borehole Technique |
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| Research Abstract |
Recent development in relation to prediction of structural stability of large rock cavern has indicated the need for systematic stress measurements in the field, e.g. systematic measurement of the stress distributions around caverns. In the hydraulic fracturing to determine the state stress at a certain point within a rock mass, the fracture phenomena of a borehole surface, which is a function of the field stress, needs to be measured by applying hydraulic pressure into the borehole. Hydraulic fracturing with hemispherical-ended borehole is very similar to conventional hydraulic fracturing except for the location of applying hydraulic pressure, namely the pressure at the borehole bottom surface which is formed hemispherically. This method has a possibility to measure the three dimensional stress state in rock mass in a single borehole.
Firstly, hydraulic fracturing of spherical cavity in infinite rock mass is suggested. Then the fracture phenomena are analyzed by the stress coefficients determined theoretically on the surface of the cavity. It is clarified that two magnitudes and three directions of the principal stresses of rock stress are determined by this method. Secondly hydraulic fracturing with hemispherical-ended borehole is suggested and the stress coefficients are determined by FEM for analyzing fracture phenomena at borehole bottom surface. Finally, analyzing the fracture phenomena on the hemispherical-ended borehole surface under general three dimensional rock stresses, it is made clear that those are dominated by the deferential stress, the directions of principal stresses, the tensile strength of rock mass and so on. It is concluded that the rock stress can be determined by the hydraulic fracturing with hemispherical-ended borehole.
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