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2020 Vol.30, Issue 3 Preview Page

Research Article

Delineation of the Slip Weak Zone of Land Creeping with Integrated Geophysical Methods and Slope Stability Analysis

복합 지구물리탐사와 사면 안정해석 자료를 이용한 땅밀림 지역의 활동연약대 파악

Sun-Joong Lee12
,
Ji-Soo Kim3*
,
Kwan-Soo Kim24
,
Il-Ryong Kwon25
이 선중12
,
김 지수3*
,
김 관수24
,
권 일룡25
1Researcher, Forest Technology Division, National Forestry Cooperative Federation
2Doctoral Student, Department of Earth & Environmental Sciences, Chungbuk National University
3Professor, Department of Earth & Environmental Sciences, Chungbuk National University
4Researcher, Korea Polar Researcher Institute
5CEO, Podo Inc.
1산림조합중앙회 산림종합기술본부 연구원
2충북대학교 지구환경과학과 박사과정
3충북대학교 지구환경과학과 교수
4극지연구소 연구원
5주식회사 포도 대표이사
*Corresponding Author
30 September 2020. pp. 289-302
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Abstract

To determine the shallow subsurface structure and sliding surface of land creeping in 2016 at Hadong-gun, Gyeongsangnam-do, geophysical surveys (electric resistivity, and refraction seismic methods, borehole televiewer) and slope stability analysis were conducted. The subsurface structure delineated with borehole lithologies and seismic velocity structures provided the information that the sediment layer on the top of the slope was rather as thick as 20 m and the underlying weathered rock (anorthosite) was thinner than 1 m. Based on the tension cracks observed during the geological mapping, televiewer scanning was performed at the borehole BH-2 and detected the intensive fracture zones at the ground-water level, associated with the slip weak zones mapped in dipole-dipole electrical resistivity section. Downslope sliding and slightly upward pushing at the apex of high resistive bedrock explains the curved slip plane of the land creeping. Such a convex structure might play a role of natural toe abutment for preventing the downward development of slip weak zones. In slope stability analysis, the safety factors of the slip weak zone are calculated with varying the groundwater levels for dry and rainy seasons and the downslope is founded to be unstable with safety factor of 0.89 due to fully saturated material in rainy season.

Keywords
land creeping
integrated geophysical survey
tension crack
slope stability analysis
slip weak zone

2016년 경상남도 하동군 땅밀림 지역의 지하구조와 미끄럼사면을 파악하기 위해 지구물리탐사(전기비저항, 탄성파 굴절법, 시추공 영상촬영)와 사면안정해석을 실시하였다. 시추조사와 탄성파속도로 해석된 사면의 지층 및 지하구조는 20여 m의 두터운 퇴적층 밑에 구간에 따라 1 m보다 얇은 풍화암 및 연암이 각각 분포한다. 지표지질조사를 통하여 관찰된 인장균열의 지표흔적을 기준으로 시추공 BH-2에서 영상촬영을 수행하여 확인된 집중 파쇄대의 분포는 지하수면과 쌍극자배열 전기비저항 단면에서 해석된 활동연약대의 깊이와 잘 부합한다. 기반암 표면의 고비저항 돌출부는 연약대의 하부 진행을 막는 일종의 자연적인 받침대 역할을 하여 이것을 경계점으로 활동면이 미끄러지고 약간 위로 올라가는 휘어진 파괴면을 수반하는 땅밀림의 특성을 설명해준다. 활동연약대에 대한 사면안정해석에서 지하수면의 변동시켜가며 건기와 우기의 안전율을 계산한 결과 우기에 해당되는 0.89의 낮은 값은 지하수로 완전포화된 물질에 기인하는 바 조사지역의 사면은 호우 시 불안정한 사면으로 해석된다.

키워드
땅밀림
복합지구물리탐사
인장균열
사면안정해석
활동연약대
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Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 30
  • No :3
  • Pages :289-302
  • Received Date : 2020-08-24
  • Accepted Date : 2020-09-05
  • DOI :https://doi.org/10.9720/kseg.2020.3.289
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