Gravity Field Interpretation of a Geological Anomaly Zone Responsible for Slope Failure

Sungchan Choi; Sung-Wook Kim; Eun-Kyeong Choi; Dae-Hong Go; Yeong-Jae Lee; Myeong-Joo Oh

doi:10.9720/kseg.2026.1.115

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2026 Vol.36, Issue 1 Preview Page Next Page

Research Article

Gravity Field Interpretation of a Geological Anomaly Zone Responsible for Slope Failure 비탈면 붕괴를 유발한 지질이상대의 중력장 해석

31 March 2026. pp. 115-127

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Abstract

A slope failure case that occurred at a road cut slope adjacent to the Yangsan Fault was analyzed from the perspective of gravity field interpretation to investigate failure mechanisms that are difficult to resolve through conventional surface geological surveys and limited borehole investigations. The failure occurred after completion of reinforcement works, indicating that artificial excavation or localized drainage conditions alone are insufficient to explain the collapse. To interpret subsurface density structures, an initial geological model was constructed by integrating geomorphological and geological information with electrical resistivity survey results, followed by gravity field interpretation and three-dimensional density modeling. Electrical resistivity surveys show laterally continuous low-resistivity zones and zones of differential weathering beneath the collapse area, while residual gravity anomalies reveal a distinct linear low-density zone developed below the failed slope. Results of three-dimensional density modeling indicate that profiles crossing the collapse area exhibit a marked reduction in gravity values and an increase in the thickness of low-density layers compared to surrounding areas, which are interpreted as a covered geological anomaly associated with a concealed fault. The study slope is spatially located within the damage zone of the Yangsan Fault, where rock fracturing, differential weathering, increased permeability, and density reduction related to fault activity act in combination to form a structurally vulnerable zone. Low-gravity anomalies and corresponding low-density zones identified through gravity field interpretation represent key physical indicators of subsurface geological anomalies that are difficult to recognize during investigation, design, and construction stages. These results demonstrate that gravity-based interpretation provides an effective tool for identifying the causes of repeated slope failures and for establishing disaster mitigation strategies in areas adjacent to major fault zones.

Keywords

cut slope

gravity field interpretation

geological anomaly

concealed fault

density model

양산단층에 인접한 도로 비탈면에서 발생한 붕괴 사례를 대상으로, 기존의 지표 지질조사와 제한적인 시추조사로 규명되기 어려운 붕괴 원인을 중력장 해석 관점에서 분석하였다. 붕괴는 보강 공사가 완료된 이후 발생하였으며, 인공 절개나 국지적인 배수 조건만으로는 원인을 설명하기 어려운 특징을 보인다. 지층의 밀도 구조를 해석하기 위해 지형·지질 환경 정보와 전기비저항탐사 결과를 통합하여 초기 지층 구조 모형을 구축하고, 이를 바탕으로 중력장 해석과 3차원 밀도 모델링을 수행하였다. 전기비저항 탐사에서는 붕괴 구간 하부를 따라 저비저항대와 차별 풍화대가 연속적으로 분포하며, 잔여중력이상에서는 붕괴 구간 하부에 선형으로 발달하는 저밀도층이 뚜렷하게 나타난다. 3차원 밀도 모델링 결과, 붕괴 구간을 횡단하는 단면에서 주변에 비해 중력이 현저히 감소하고 저밀도층의 두께가 증가하는 지질이상대가 관찰되며, 이는 피복된 숨은단층으로 추정된다. 대상 비탈면은 공간적으로 양산단층 손상대에 속하며, 단층 작용에 따른 파쇄, 차별 풍화, 투수성 증가 및 밀도 감소가 복합적으로 작용한 구조적 취약 구간임을 보여준다. 중력장 해석에서 확인된 저중력이상과 이에 대응하는 저밀도층은 조사와 설계, 시공 중 인지하기 어려운 지질이상대를 나타내는 주요한 지표로 판단되며, 대규모 단층대에 인접한 지역에서 반복적으로 발생하는 비탈면 붕괴의 원인 규명과 재해 저감 전략 수립에 효과적으로 활용될 수 있다.

키워드

도로비탈면

중력장 해석

지질이상대

숨은단층

밀도 모형

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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 : 36
No :1
Pages :115-127
Received Date : 2026-02-11
Revised Date : 2026-03-13
Accepted Date : 2026-03-18
DOI :https://doi.org/10.9720/kseg.2026.1.115

The Journal of Engineering Geology ISSN:1226-5268(Print) 2287-7169(Online) 지질공학

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