A Trend of Back Ground Surface Settlement of Braced Wall Depending on the Joint Dips in Rocks under the Soil Strata

Sang-Su Bae; Sang-Duk Lee

doi:10.7843/kgs.2016.32.11.83

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2016 Vol.32, Issue 11 Preview Page Next Page

A Trend of Back Ground Surface Settlement of Braced Wall Depending on the Joint Dips in Rocks under the Soil Strata 복합지반 굴착 시 암반층 절리경사 각도별 흙막이 벽체 배후 지표침하의 경향

30 November 2016. pp. 83-96

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Abstract

The surface settlement of the back ground of a braced wall due to the ground excavation has the great influence on the safety of the surrounding area. But it is not easy to predict the settlement of the surrounding area due to proud excavation. Estimation of the settlement of the surface ground induced by the deformation of the braced wall is performed by FEM and empirical method (Peck, Clough etc). In this research, surface settlement of the back ground braced wall depending on the joint dips in rocks during excavating the composit ground was measured at the large scale model test (standard: 0.3 m × 0.3 m × 0.5 m). The scale of model test was 1/14.5 and the ground was excavated in ten steps. Earth pressure on the braced wall and ground surface settlement on the back ground of a braced wall were investigated. The surface settlement during the excavation depended on the joint dips in rocks on of the ratio of rock layer. Maximum earth pressure and maximum surface settlement were masured at the same excavation step. In accordance with the increase of the rock layer dips and rock layer ratio, the ground surface settlement increased. The maximum ground surface settlement was 17 times larger at 60 degree joint dips in rocks than that of the horizontal ground conditions. And the position of the maximum surface settlement by empirical method was calculated at the point, which was 17%∼33% of excavation depth. In accordance with the increase of the rock layer dips and rock layer ratio, the ground maximum surface settlement increased. The ground surface settlement of composite ground is smaller than that of the empirical.

Keywords

Composit ground

Ground surface settlement

Jointed Rock layers

Large scale model test

흙막이 벽체 배후지반의 지표 침하는 인접구조물의 안전성에 많은 영향을 미친다. 그러나 지반굴착에 따른 주변 지반의 침하는 예측하기가 쉽지 않고 굴착면으로부터 이격거리에 따른 침하량을 정량적으로 구하는 것은 더욱 어려운 일이다. 흙막이 벽체의 변형에 의한 지표침하는 수치해석(FEM)이나, 경험적 방법 Peck(1969)등으로 추정하고 있으나 주로 토사층을 대상으로 하고 있다. 본 연구에서는 토사층 하부에 암반층이 위치하는 복합지반을 굴착 할 때 암반층의 깊이와 절리경사에 따른 흙막이 벽체 배후지반의 지표침하를 대형모형실험(규격: 3m×3m×0.5m)을 수행하여 측정하였다. 모형실험은 축척 1/14.5로 하고 10단계로 굴착을 하였다. 암반층 비율은 35%와 50%로 하였고 암반층의 절리경사를 0°, 30°, 45°, 60°로 하여 단계굴착하면서 흙막이 벽체 버팀대에 작용하는 토압(Lee 2014)과 흙막이 벽체 배후지반의 지표 침하량을 측정하였다. 암반층비율과 암반층 절리경사가 증가하면 배후지반의 지표침하량도 증가하며 암반층 절리경사 60°(J60)에서는 수평지반 굴착시에 비해 최대 17배 크게 발생하였다. 흙막이벽체 배후지반에서 최대 지표침하는 경험적 방법과 달리 흙막이 벽체로부터 굴착깊이의 17%∼33%만큼 이격된 위치에서 가장 크게 발생하였다. 복합지반의 지표침하는 전반적으로 경험적 추정방법에 의한 지표침하량에 비해 작게 나타났다.

References

1.Clough, G. W. and O’Rourke, T. D. (1990), “Construction Induced Movements of in Situ Walls”, Proc., Design and Performance of Earth Retaining Structure, Geotechnical Special Publication No. 25, ASCE, New York, pp.439-470.

2.Hwang, Seung Hyeon (2010), Design of Earth Retaining Structures, C.I.R, Seoul, pp.373-397.

3.Kim, Hong Moon (2009), “Pillar Load and Ground behavior Around the Two-arch Tunnel in Discontinuous Ground”, Doctorate thesis, Ajou University-Graduate School, pp.115

4.Kim, Il (2008), “Behavior of the Tunnel below a Building Depending on the Pre-loading on Braced Wall during the Adjacent Ground Excavation”, Doctorate thesis, Ajou University-Graduate School, Transportation Engineering, pp.40-44.

5.Korean Geotechnical Society (2006), Excavation and method for earth retaining structure, Goomibooks, Seoul, pp.4-20.

6.Lee, Sang Duk (1994), Safet Lay out and Construction of Safey undergroud structure, Saeron, Seoul, pp.337-340.

7.Lee, Sang Duk (2014), Soil mechanics 4, Saeron, Seoul, pp.397-398.

8.Ministry of Construction & Transportation (1997), Standard specification for construction of city railway(subway), Korea society and civil engineers, Seoul, pp.374-380.

9.Peck, R. B. (1969), “Deep Excavations and Tunnels in Soft Ground”, Proceedings of the 7th International Conference on Soil Mechanics and Foundation Engineering, Mexico City, State of the Art Volume, pp.225-290.

Information

Publisher :The Korean Geotechnical Society
Publisher(Ko) :한국지반공학회
Journal Title :Journal of the Korean Geotechnical Society
Journal Title(Ko) :한국지반공학회 논문집
Volume : 32
No :11
Pages :83-96
Received Date : 2016-09-13
Revised Date : 2016-10-10
Accepted Date : 2016-11-04
DOI :https://doi.org/10.7843/kgs.2016.32.11.83

Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

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