Application of GIS on Rapid Evaluation for Potential Portal Areas of Tunnels

Abstract:

Stability of tunnel portal depends on lots of factors, such as existing topography, engineering geology, hydrogeology as well as portal layout designated and stability measurements adopted, etc. Location of portals is one of the most important issues for route selection and planning stage of tunnel engineering. Thus, it is usually a mission of well-experienced engineers and also a time-consuming task. Recently, the well development of geographic information system (GIS) provides a better way to assess the slope stability of potential area for tunneling. There are great numbers of researches focusing on the evaluation on potential hazard or stability degree of existing slopes; however, the potential instability caused by possible excavation due to layout designation is seldom to be taken into account in these researches. Consequently,the present work aims to set up a GIS based method, considering the possible impacts caused by portal excavation, to quickly assess the stability of portal. First, the conventional profiles used in portals are taken into account and typical excavated slope ratios are introduced. Then, based on the digital elevation model, the potential excavated area for a location with considered elevation, said the critical wedge, can be determined accordingly. The analysis method for infinite slope is then applied to evaluation the stability of the critical wedge. Comparison with the results from slice method shows that the proposed method provides a reasonable estimation. Application to a tunnel with 6 portals, some instability occurred during construction, meets well with the situations. Using the embedded function of GIS, the safety factor then can be obtained by means of the proposed method. As various slope ratios and distinct elevation are considered, the analyzed results provide valuable information for tunnel portal selection.

• Periodical: Applied Mechanics and Materials (Volumes 479-480)
• Pages: 1056-1060
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.479-480.1056
• Online since: December 2013
• Authors: Iau Teh Wang
• Keywords: Geographic Information System (GIS), Portal, Site Selection, Slope Stability

References

[1] E. Hoek and E.T. Brown, in: Underground Excavations in Rock, The Institute of Mining and Metallurgy, London, (1980).

[2] W.L. Wang, J. Li, T. T Wang and Z.J. Wang: Designs and constructs retrospect of tunnel portal of Taiwan - Statistical analysis of the case, The 3th International Conference on Structural and Civil Engineering Research, Taipei, (2003), pp.103-108.

[3] L. Lucia and P. Floriana, Applications of statistical and GIS techniques to slope instability zonation (1: 50000 Fabriano geological map sheet), Soil Dynamics and Earthquake Engineering, Vol. 15 (1980), pp.83-94.

DOI: 10.1016/0267-7261(95)00031-3

[4] B.A. Robert, The Use of a Geographical Information System for Mapping Landslide Potential in the West Indies: University of Buffalo Press, NY, USA. pp.27-38. (1991).

[5] G. Jay, Modeling Landslide Susceptibly from a DTM in Nelson County, A Remote Sensing-GIS Approach: Virginia, pp.24-49. (1992).

[6] Y. Wang and W.S. Chen, Geology of the Coastal Range, eastern Taiwan, Central Geological Survey, MOEA, Taipei, pp.1-101. (1996).

[7] United Geotech, Inc., Drilling and design illustrating for Improve Sub-grade Engineering in Provincial Highway No. 11, Taiwan, Taipei, pp.1-66. (1997).