Stability Analysis on the Substructure of Abutment in Limestone Basin

Natural cavitied were found at shallow depth during construction of a huge bridge in Cambro-Ordovician Limestone Basin in the central part or Korea. The distribution patterns of cavities in this area were investigated carefully with a supplementary field job such as a structural geological survey, a geophysical survey, and a rock mechanical test in laboratory or field. A structural geological mapping produced a detail geological map focusing the route of the Proposed highway. It suggested that there were three faults in this wet and these faults had an influence on the mechanism of natural cavities. Among many kinds of geophysical surveys, an electrical resistivity prospecting was applied first on the specific area that was selected by results from the geological survey. Many evidences far cavities were disclosed from this geophysical data. Therefore, a seismic tomography was tested on the target wet which was focused by results from the electrical resistivity Prospecting and was believed to have several large cavities. A distinct element numerical simulation using the UDEC was followed on the target area after completing all of field surveys. Data from field tests were directly dumped or extrapolated to numerical simulations as input data. It was verified from numerical analysis that several natural cavities underneath the foundation of the bridge should be reinforced Based on the project result, finally, most of fecundations far the bridge were re-examined and the cement grouting reinforcement was constructed on several foundations among them.

석회암층 교대 하부 구조물의 안정성 해석

중부지역에 존재하는 대규모 석회암층을 통과하는 고속도로가 신설되는 가운데, 일부 교량의 교대 하부 얕은 심도에서 자연 생성된 석회암 공동이 다수 발견됨에 따라. 교대 및 교량의 안정성 확보를 위한 추가 정밀조사가 실시되었다. 정밀구조지질조사를 통해 고속도로 노선을 따른 지질도가 작성되었으며 이를 토대로 전기비저항 탐사가 일부 구간에 대해 실시되었다. 이 결과 석회암 공동의 존재가 의심되는 부분에 대해 국부적 인 탄성파탐사가 수행됨으로써 석회암 공동의 위치 및 규모가 최종 파악되었으며, 일련의 현장조사 및 실험실 시험결과를 이용한 수치해석이 이루어졌다. 수치해석에 의한 교대 및 교량의 안정성 분석 결과, 시멘트 그라우팅에 의한 교량하부 기초의 보강이 제안되었다.