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http://dx.doi.org/10.9720/kseg.2015.1.115

Case Study of the Stability of a Large Cut-Slope at a Tunnel Portal  

Park, Dong Soon (K-water Research Institute, Korea Water Resources Corporation)
Bae, Jong-Soem (K-water Research Institute, Korea Water Resources Corporation)
Publication Information
The Journal of Engineering Geology / v.25, no.1, 2015 , pp. 115-129 More about this Journal
Abstract
The cut-slope of a large-sectional tunnel portal is recognized as a potential area of weakness due to unstable stress distribution and possible permanent displacement. This paper presents a case study of a slope failure and remediation for a large-scale cut-slope at a tunnel portal. Extensive rock-slope brittle failure occurred along discontinuities in the rock mass after 46 mm of rainfall, which caused instability of the upper part of the cut-slope. Based on a geological survey and face mapping, the reason for failure is believed to be the presence of thin clay fill in discontinuities in the weathered rock mass and consequent saturationinduced joint weakening. The granite-gneiss rock mass has a high content of alkali-feldspar, indicating a vulnerability to weathering. Immediately before the slope failure, a sharp increase in displacement rate was indicated by settlement-time histories, and this observation can contribute to the safety management criteria for slope stability. In this case study, emergency remediation was performed to prevent further hazard and to facilitate reconstruction, and counterweight fill and concrete filling of voids were successfully applied. For ultimate remediation, the grid anchor-blocks were used for slope stabilization, and additional rock bolts and grouting were applied inside the tunnel. Limit-equilibrium slope stability analysis and analyses of strereographic projections confirmed the instability of the original slope and the effectiveness of reinforcing methods. After the application of reinforcing measures, instrumental monitoring indicated that the slope and the tunnel remained stable. This case study is expected to serve as a valuable reference for similar engineering cases of large-sectional slope stability.
Keywords
large sectional tunnel; slope stability; tunnel portal; remediation; rock slope;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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1 Chun, B. S. and Shin, Y. W., 2004, Application of counterweight fill to insure slope stability near the tunnel entrance, Annual Conference of the Korean Geo-Environmental Society, September, Cheongju, Korea (in Korean with English abstract).
2 Abramson, L. W., Lee, T. S., Sharma, S., and Boyce, G. M., 2002, Slope stability and stabilization methods, John Wiley & Sons, 736p.
3 Baek, Y., Koo, H. B., and Yoo, K. J., 2002, A study on the stability analysis and countermeasure of tunnel portal failure slope - in Suanbo hot springs 1 and 2 tunnel failure site, The Journal of Engineering Geology, 12(4), 367-378 (in Korean with English abstract).
4 Barton, N., 1973, Review of a new shear-strength criterion for rock joints, Engineering Geology, 7(4), 287-332.   DOI
5 Collins, B. and Znidarcic, D., 2004, Stability analyses of rainfall induced landslides, Journal of Geotechnical and Geoenvironmental Enginnering, 130(4), 362-372.   DOI
6 Fuchsberger, M., 2008, Slope failure at a major cut for a motorway in Austria - Its cause and its stabilisation, From Research to Practice in Geotechnical Engineering, 616-625.
7 Goodman, R. and Kieffer, D., 2000, Behavior of rock in slopes, Journal of Geotechnical and Geoenvironmental Enginnering, 126(8), 675-684.   DOI
8 Jang, J. H., 2013, The applicability of the pressure type nailing method to prevent the collapse of the cut slope, MSc thesis, Kyunggi University, 73p (in Korean).
9 Kim, Y. J., Lee, Y. H., Kim, S. K., and Kim, J. H., 2006, Case study on failure of rock slope caused by filling material of clay, Tunnel & Underground Space, 16(5), 368-376 (in Korean with English abstract).
10 Jiaoa, J. J., Wangb, X. S., and Nandy, S., 2005, Confined groundwater zone and slope instability in weathered igneous rocks in Hong Kong, Engineering Geology, 80(1-2), 71-92.   DOI
11 Kim, H., Lim, D. H., Park, S. H., Yoon, H. D., Lee, H. G., and Kang, M. G., 2004, The case study of slope failure on tunnel portal, Annual Conference of the Korean Society of Civil Engineers, December 16, Seoul, Korea, 109-121 (in Korean with English abstract).
12 Kim, N. Y., Kim, H. J., and Park, Y. S., 2010, A study of road tunnel exit slope collapse by Gneiss folation, Annual Conference of the Korean Geo-Environmental Society, September 2-3, Seoul, Korea, 487-496 (in Korean with English abstract).
13 Koo, H. B., Kim, S. H., Rhee, J. H., and Kim, J. H., 2008, A case study of collapse at tunnel portal adjacent to the large cut slope, Annual Conference of the Korean Society of Hazard Mitigation, Feburary 28, 573-576 (in English with Korean abstract).
14 Korea Expressway Corporation, 1997, A study on the stabilization and protection measures (II), Research Report (in Korean).
15 Kwon, O. I., Baek, Y., and Park, C. H., 2010, A case study on stability analysis of tunnel portal slope, Annual Conference of the Korean Society of Engineering Geology, April 8-9, Gyeongju, Korea, 249-253 (in Korean).
16 Kyeryong Construction Industrial co., Ltd., 2013, A report on slope stabilization near tunnel portal, April (in Korean).
17 Lee, J. Y., 2009, Causal factor analyses and reinforcement scheme of big cut slope failure: an example in Okcheon area, MSc thesis, Paichai University, 79p (in Korean).
18 Yang, H. Y., 2013, A case study on the design and construction of large cutting-slope in colluvial soil, MSc thesis, Sunchon University, 58p (in Korean with English abstract).
19 Ministry of Land, Infrastructure and Transport, 2011, Design guideline for slopes in construction project (in Korean).
20 Na, H. S., 2013, A case study on reinforcement method for failure of rock slope, MSc thesis, Chosun University, 64p (in Korean).
21 Wang, Y., 2014, The Tom Lantos tunnels at Devil's Slide Project, The longest highway tunnels in California, Challenges and Advances in Sustainable Transportation Systems, 459-466.