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Research Article

Soil Properties of Granitic Weathered Soils in the Landslide-prone Areas in Seoul

서울지역 화강암 풍화토 토층지반의 토질특성

Kyeong-Su Kim1*
김 경수1*
1Geo-Environmental Hazards Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea, Principal Researcher
1한국지질자원연구원 지질환경재해연구센터, 책임연구원
*Corresponding Author
31 March 2019. pp. 23-35
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Abstract

Landslides occur due to heavy rainfall in the summer season. Some of water may infiltrate into the ground; it causes a high saturation condition capable of causing a landslide. Soil properties are crucial in estimating slope stability and debris flow occurrence. The main study areas are Gwanaksan, Suraksan and Bukhansan (Mountain) in Seoul. A total of 44 soil samples were taken from the study area; and a series of geotechnical tests were performed. Physical and mechanical properties were obtained and compared based on region. As a result, among well-graded soils, they are classified as a clayey sand. Coarse-grained and fine-grained contents are approximately 95% and 5%, respectively, with very low amount of clay content. Density, liquid limit and dry unit weight are ranged in 2.62~2.67 g/cm3, 27.93~38.15% and 1.092~1.814 g/cm3. Cohesion and internal friction angle are 4 kPa and 35° regardless of mountain area. Coefficient of permeability is varied between 3.07×10-3~4.61×10-2 cm/sec; it means that it results in great seepage. Permeability is inversely proportional to the uniformity coefficient and is proportional to the effective particle size. In the formal case, there was a difference by mountain area, while in the latter, the tendency was almost similar.

Keywords
Seoul
natural slope
landslide
granitic weathered soil
soil properties

우리나라의 경우 자연사면에서 발생되는 산사태는 대부분 여름철의 집중호우에 기인되며 주로 토층지반에서 발생된다. 집중호우로 인해 자연사면의 토층지반이 포화되고 지반지지력이 약화되어 사면붕괴 가능성이 높아진다. 사면안정성과 토석류 확산성 평가시에는 지반의 토질특성 분석이 필수적이다. 본 연구는 서울지역 주요 산지 관악산, 수락산과 북한산에 분포한 화강암토층지반을 대상으로 총 44개소에서 시료를 채취하여 물리·역학적 특성에 관한 지반공학시험을 통한 토질특성을 분석하였다. 그리고 산사태 발생 유발인자와 관계되는 토질의 물성과 공학특성을 산지별로 구분하여 대비하고 토질물성 간의 상관성을 분석하였다. 시험분석 결과에 따르면, 연구대상지역의 토층은 전반적으로 양호한 입도의 모래 또는 점토질모래로 분류할 수 있다. 특히 조립토와 세립토 함유율이 각각 95%와 5%로 대부분 산지에서 점토함량이 매우 낮으며, 모래를 다량 함유한 토층지반으로 나타났다. 밀도, 액성한계, 그리고 습윤단위중량은 각각 2.62~2.67 g/cm3, 27.93~38.15% 및 1.092~1.814 g/cm3인 것으로 나타났다. 점착력과 내부마찰각은 각각 4 kPa 및 35°로서 산지별 큰 차이가 없었으며, 투수계수는 3.07×10-3~4.61×10-2 cm/sec로서 보통~빠른 정도의 투수성지반으로 평가되었다. 투수계수는 균등계수와 반비례적 관계이고, 유효입경과는 비례적인 관계로 나타났다. 투수계수와 균등계수 관계식은 산지별로 다소 차이를 보이는 반면, 투수계수와 유효입경은 산지별로 거의 유사한 경향성을 보였다.

키워드
서울지역
자연사면
산사태
화강암 풍화토
토질특성
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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 : 29
  • No :1
  • Pages :23-35
  • Received Date : 2019-02-28
  • Revised Date : 2019-03-21
  • Accepted Date : 2019-03-26
  • DOI :https://doi.org/10.9720/kseg.2019.1.023
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