Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Countermeasures for Slope Stability on Coal-Seam Bearing Mudstone Using the Geological Cross-Sections

지질횡단면도를 이용한 함탄층이암 비탈면의 안정성 검토

  • 임명혁 (대전대학교 건설안전방재공학과)
  • Received : 2021.02.15
  • Accepted : 2021.03.30
  • Published : 2021.04.30
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Abstract

The subject of this study is a rock slope composed of coal bearing mudstone that unconformably covers the Cenozoic Tertiary basalt strata in Pohang. Discontinuities developed within the slope are stratification and nonconformity, cooling joint and shear joint. As for the type and size of rock-failure by section, circular failure is dominant in the upper coal bearing mudstone section, and toppling failure is dominant in the lower basalt section, and the failure size of rock body is about 0.02 m to 0.01 m3 on average. As a result of synthesizing face-mapping data, SMR, physical properties/mechanical tests of soil and rocks, stereonet projection analysis, geological cross-sectional view analysis and limit equilibrium analysis for each section, all of the representative sections were significantly less than the allowable safety factor, requiring a countermeasure method. After applying the slope relief method and the rock anchor method as well as the green soil surface treatment method + installation of rockfall prevention fence, the safety factors of slope exceeded the allowable safety factor. Creating a geological cross-section of a representative section perpendicular to the slope, face-mapping data, and a limit equilibrium analysis reviewed by using the geological cross-section as a representative cross-section will be a reasonable tool for three-dimensional analysis of the slope stability. In the case of rock slopes that have developed stratification and nonconformity and are loosed such as coal bearing mudstone, it is essential to prepare systematic geological cross-sections. For the representative cross section used in the limit equilibrium analysis, it is reasonable to set the geological cross section for each section as the basic cross section.

연구 대상은 포항 지역의 신생대 제3기 현무암 지층을 부정합적으로 피복하고 있는 함탄층이암으로 구성된 절취 암반비탈면으로서 불연속면은 층리와 부정합, 수축절리 및 전단절리가 발달한다. 구간별로 파괴의 유형과 규모는 상부 함탄층이암 구간은 원호파괴, 하부 현무암 구간은 전도파괴가 우세하며, 파괴규모는 평균적으로 0.02 m~0.01 m3 정도이다. face-mapping 자료, SMR, 토사와 암석의 물성·역학시험, 평사투영해석과 구간별 지질횡단면도 분석 및 한계평형해석으로 종합한 결과, 대표단면 모두 허용 안전율에 크게 미달하여 대책공법이 필요하였다. 비탈면 안정성에 최적의 방안은 사면구배완화공법과 록앵커공법 시공과 더불어 녹생토 표면처리 공법 + 낙석방지책 설치를 적용한 후 비탈면의 안전율은 모두 허용안전율을 상회하였다. 법면 face-mapping 자료와 법면에 수직인 대표 구간의 지질횡단면도 작성, 지질횡단면도를 대표단면으로 활용하여 검토한 한계평형해석 및 그에 따른 대책공법 제시는 비탈면의 3차원 해석 및 안정성 검토의 합리적인 도구가 될 것으로 예상된다. 층리와 부정합이 발달하고 함탄층이암과 같이 이완된 암반비탈면의 경우는 체계적인 지질횡단면도의 작성이 필수불가결하며, 한계평형해석에 이용되는 대표단면은 반드시 구간별 지질횡단면도를 기본단면으로 설정하는 것이 합리적이다.

Keywords

References

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