1996 Fiscal Year Final Research Report Summary
The rates of increase in weathered zones and decrease in rock strength
| Project/Area Number |
07640609
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | CHUO UNIVERSITY |
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Principal Investigator |
SUZUKI Takasuke Chuo Univ. ; Fac.of Science and Engineering ; Professor, 理工学部, 教授 (60055168)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUKURA Yukinori Tsukuba Univ, ; Inst.of Geoscience ; Associate Professor, 地球科学系, 助教授 (80107341)
TAKAHASHI Ken-ichi Chuo Univ, ; Fac.of Literature ; Professor, 文学部, 教授 (40129961)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Weathering / Weathered zones / Decrease in rock strength / Weathering rates / Rock properties / Mudstone / Sandstone |
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| Research Abstract |
The weathering rates of bedrock under dated erosional terraces were concluded as follows.
(1) The empirical equations were established to express the rates of increase in the thickness of each of four weathered zones, i.e.highly, moderately, slightly and faintly weathered zone. The relationships between the thickness of weathered zone (Z) and the weathering time (t) are expressed as Z=alphat^<beta>, Whera alpha and beta are constants. It is concluded that (1) the rates of increase in thickness of each weathered zone (dZ/dt) are not constant, but decelerate with time (t) gradually, and (2) the zones with lower weathering grades have a faster weathering rate.
(2) Comparism with mudstone and sandstone in the weathering rates (dZ/dt) shows that at first mudstone have larger weathering rates which increase in thickness of weathered zones than sandstone. The weathering rates of mudstone are decelerate with time and finally are passed by sandstone.
(3) The empirical equation that shows the rate of decrease in strength at arbitrary depth from the bedrock surface are established. Mudstone and sandstone have no change in strength from the start of weathering to the point where decrease in strength rapidly (t=7.8d^<1.2> in sandstone, t=4.2d^<1.4> in mudstone).
(4) Compare with mudstone and sandstone in the rate of decrease in strength (dR/dt), at the point near the bedrock surface, mudstone have larger than sandstone in weathering rates. On the order hand, at the deep point where deeper than 30cm from the surface, sandstone have lager than mudstone in weathering rates.
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