1991 Fiscal Year Final Research Report Summary
Initial Stress Measurements in Rock using a Conical-Shaped Strain-Gage Cell
| Project/Area Number |
02650344
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
基礎・土質工学
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| Research Institution | Kyoto University |
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Principal Investigator |
KOBAYASHI Shoichi Kyoto Univ. Faculty of Eng., 工学部, 教授 (90025908)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIMURA Naoshi Kyoto Univ. Faculty of Eng. Instructer, 工学部, 助手 (90127118)
TAMURA Takeshi Kyoto Univ. Faculty of Eng. Assoc. Professor, 工学部, 助教授 (30026330)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Initial-stress / Stress-relief / Conical-end strain-gage method / Conical-shaped strain-gage cell / Stres-sensitivity / Observation equation / Boundary element methods / Improved conical-end strain-gage method |
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| Research Abstract |
As a result of this research, we proposed a new convenient and efficient method for measuring initial stresses in a rock using only one conical-ended borehole applying a newly-developed conical shaped strain-gage cell at the bottom of It in conjunction with the overcoring technique and testified the usefullness of the proposed method at a site of an underground power house. The main achievements are as follows :
1)On measurements
a)We determined accurately the stress-sensitivity coefficients(strains due to the unit initial stress)for the conical-end shape and conical-end shape with a small hole ahead of it(the improved version)by use of the boundary element methods.
b)We determined the observation equations for arbitrary numbers of measured strain components using the least-squares method.
c)We proposed a method for determinig accurate stresses from the strains measured at only one borehole.
2)On instruments and implinqntation
a)We proposed an efficient strain measurement technique at the bottom of the conical-end of a borehole by using a newly-developed conical-shaped strain gage cell having 12 components with 6 cross-gages equidistantly-spaced on the surface of the shell.
b)We proposed a technique to control the vertical direction of the strain-gage cell at the conical-end borehole using an unboned-type strain-gage accelogeter.
c)We developed a diamond-solded bit for shaping the conical end of a borehole.
d)Improving the suibel of the boring machine, we made it possible to measure strains during the progress of boring.
e)An improvement was made for recognizing the rock state behind the conical-end of a borehole simply boring a small-sized hole ahead of the conical-end(an improvement).
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