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Setting of the range for shear strength of fault cores in Gyeongju and Ulsan using regression analysis

회귀분석을 이용한 경주·울산 지역에 분포하는 단층 핵의 전단강도 범위 설정

Hyun-Seok Yun1
,
Seong-Woo Moon1
,
Yong-Seok Seo2*
윤 현석1
,
문 성우1
,
서 용석2*
1Chungbuk National University, Dept. of Earth and Environmental Sciences, Ph. D Student
2Chungbuk National University, Dept. of Earth and Environmental Sciences, Professor
1충북대학교 지구환경과학과 박사과정
2충북대학교 지구환경과학과 교수
*교신저자. *Corresponding Author. 
31 March 2015. pp. 127-140
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Abstract

A fault is one of the critical factors that may lead to a possible ground collapse occurring in construction site. A fault core, however, possibly acting as a failure plane in whole fault zone, is composed of fractured rock and gouge nonuniformly distributed and thus can be characterized by its wide range of shear strength which is generally acquired by experimental method for stability analysis. In this study, we performed direct shear test and grain size distribution analysis for 62 fault core samples cropped from 12 different spots located in the vicinity of Kyongju and Ulsan, Korea. As a result, the range of shear strength representing the characteristics of fault cores in the study regions is determined with regard to vertical stress using a regression analysis for experiment data. The weight ratio of gravels in the samples is proportional to the shear strength and that of silt and clay is in inverse proportion to the shear strength. For most samples, the coefficient of determination is over 0.7 despite of inhomogeneity of them and consequently we determined the lower limit and upper limit of the shear strength with regard to the weight ratio by setting the confidence interval of 95%.

Keywords
Fault zone
Fault cores
Shear strength
Grain size
Regressin analysis
95% confidence interval

단층은 굴착공사 중 발생하는 붕괴의 주요원인 중 하나이다. 하지만 단층대 내에서 주요 파괴면으로 작용하는 단층 핵은 파쇄암과 가우지가 불균질하게 분포하는 부분으로서 전단강도의 분포범위가 넓기 때문에 안정성 해석 시 경험적으로 결정되는 경우가 많다. 본 연구에서는 경주와 울산의 12개 지점에서 채취한 62개의 단층 핵 시료를 대상으로 직접전단시험과 입도 분석을 수행하였다. 실내시험으로 얻어진 결과를 이용하여 회귀 분석을 수행하여 수직응력별 입도에 따른 전단강도의 범위를 결정하였다. 자갈의 무게비는 전단강도와 비례하며, 실트 및 점토의 무게비는 반비례하는 것으로 나타났다. 결정계수는 대부분 약 0.7 이상으로 시료의 불균질성을 고려할 때 비교적 높게 나타났으며, 분석된 회귀모형의 95% 신뢰 구간을 설정하여 무게비에 따른 전단강도의 상한과 하한 범위를 결정하였다.

키워드
단층대
단층 핵
전단강도
입도
회귀분석
95% 신뢰구간
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Information
  • Publisher :Korean Tunneling and Underground Space Association
  • Publisher(Ko) :한국터널지하공간학회
  • Journal Title :Journal of Korean Tunnelling and Underground Space Association
  • Journal Title(Ko) :한국터널지하공간학회 논문집
  • Volume : 17
  • No :2
  • Pages :127-140
  • Received Date : 2015-03-04
  • Revised Date : 2015-03-13
  • Accepted Date : 2015-03-16
  • DOI :https://doi.org/10.9711/KTAJ.2015.17.2.127
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