Risk management of rock avalanche using index of chemical weathering

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K13579
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Yamaguchi University
• Principal Investigator: Owada Masaki 山口大学, 大学院創成科学研究科, 教授 (50213905)
• Co-Investigator(Kenkyū-buntansha): 亀井 淳志 島根大学, 総合理工学研究科, 教授 (60379691)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 花崗岩体 / 化学的風化 / 化学的風化指標 / 土石流

Outline of Final Research Achievements

Some of chemical index are powerful tools for estimating degree of chemical weathering. I determined the chemical compositions from fresh to decomposed granitic rocks using CN(CaO+Na2O), A(Al2O3), K(K2O) diagram, and can classify these rocks into three types; Type 1 to Type 3 with increasing degree of weathering. Type 1 shows decreasing CN from fresh to decomposed rocks. Type 2 indicates increasing K at the beginning of weathering, then decreasing CN. A chemical trend of Type 3 are similar to that of Type 1 but it finally shows decreasing K. Type 2 is most dominant type of chemical weathering in the rock-avalanched fields. It suggests that the cause of decomposed granitic rocks is affected by hydrothermal alteration, and the chemical weathering of Type 2 could be a useful index for the risk of rock avalanche.

Free Research Field

地質学