2003 Fiscal Year Final Research Report Summary
Study on rock weathering on steep slopes for prediction of rock fall
| Project/Area Number |
14340149
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Shimane University |
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Principal Investigator |
YOKOTA Shinichiro Shimane University, Fac.of Science and Engineering, Professor, 総合理工学部, 教授 (60211653)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIYAMA Ken'ichi Tokushima University, Fac.Liberal Arts, Assistant, 総合科学部, 助手 (60363131)
MASUMOTO Kiyoshi Shimane University, Fac.of Science and Engineering, Lectuler, 総合理工学部, 講師 (00238916)
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| Project Period (FY) |
2002 – 2003
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| Keywords | weathering / salt weathering / tafoni / rock fall / rock mass / pipe flow / infiltration / disaster |
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| Research Abstract |
Configuration and characteristics of 'tafoni', tiny caves developed on rock exposures, have been surveyed in some steep slopes, southwest Japan. Tafoni is closely related to salt weathering of rocks. Then, contents and textures of rocks, and their weathered degree have been measured in many tafoni in addition to their configurations. Numerous fallen rock blocks on the foot of steep slopes where tafoni developing mean the frequently occurrences of rock fall from such slopes. Because over hanged blocks just above tafoni tend to become unstable with its developing.
Tafoni shapes generally lenticular ellipsoids elongating along bedding planes. It also has a deep concave roof, visors, and flat floor in its profile. It also tends to appear within coarse-grained arenite sandstones of low contents of quartz or coarse-grained tuffaceous rocks. Sometimes they contain many fragments of volcanic rocks. These rocks have low strength and high permeable properties, and include high soluble components for salt weathering.
Tafoni also tends to develop on rock exposures with plunging structure in even slightly bedding plane. High water content and highly weathered portions on roof wall indicate that infiltrated water concentrates on the roof wall, and precipitation and salt weathering proceed along it. Based on these characteristics, we can make a conceptual model indicating the processes from infiltration of rainwater to developing tafoni, and occurrence of rock fall.
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