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Analyzing the stability of a failing rock slope for suggesting suitable mitigation measure: a case study from the Theng rockslide, Sikkim Himalayas, India

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Abstract

At km 87.20 near Theng on the North Sikkim Highway, India, severe rock falls and slides in recent years rendered 180 m stretch of this important road corridor in the Sikkim Himalayas risky and vulnerable to the commuters. The rockslide at Theng has, thus, been studied in detail at 24 discrete locations using the ground-based topographic, lithologic and structural data with an objective to evaluate the mechanisms of rock sliding for suggesting the most effective mitigation measure. In this study, large scale geological mapping and site-specific kinematic analyses in different spatial domains corroborated that within this 180 m stretch, despite having a competent lithology (quartzo feldspathic gneiss and quartzites), the possibility of both plane and wedge failures are high because of gentler and unfavourably oriented planar discontinuities with respect to the available steep topography. The rock slope failure analysis both at discrete locations and in a distributed manner in a Geographic Information System further revealed that unfavourable geometric disposition of discontinuities at Theng rendered multiple modes of failure at critical locations, which is also corroborated by a very low Slope Mass Rating value (4.0) determined in this area, thus, making it difficult to suggest any cost-effective surface protection measure. However, analysis suggests slope dressing or re-excavation to contain future rock sliding in such cases, but the same appears to be difficult to implement on the ground because of unfavourable kinematic conditions of the vulnerable rock discontinuities. Accordingly, after evaluating the site conditions in detail, a short road tunnel with its probable tunnel rockmass conditions is proposed to bypass this active rock sliding stretch.

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References

  • Acharya SK (1989) The Daling Group, its nomenclature, tectonostratigraphy and structural grain: with notes on their possible equivalents. Geological Survey of India Special Publication No. 22, pp 5-13

  • Acharya SK, Shastry MVA (1979) Stratigraphy of Eastern Himalaya. Geological Survey of India Miscellaneous Publication No. 41, pp 49–67

  • Barton N, Lien R, Lunde J (1974) Engineering classification of rock masses for the design of tunnel support. Rock Mech 6:189–236

    Article  Google Scholar 

  • Bieniawski ZT (1979) The geomechanics classification in rock engineering applications. In: Proceedings of 4th congress, International Society for Rock Mechanics, Montreux, vol 2, pp 41–48

  • Champati Ray PK, Parvaiz I, Jayangondaperumal R, Thakur VC, Dadhwal VK, Bhat FA (2009) Analysis of seismicity induced landslides due to the October 8, 2005 Earthquake in Kashmir Himalaya. Curr Sci 97(3):1742–1751

    Google Scholar 

  • Dasgupta S, Ganguly J, Neogi S (2004) Inverted metamorphic sequence in the Sikkim Himalayas: crystallization history, P–T gradient and implications. J Metamorph Geol 22:395–412

    Article  Google Scholar 

  • De Kemp EA (1998) Three-dimensional projection of curvilinear geological features through direction cosine interpolation of structural field observations. Comput Geosci 25(3):269–284

    Article  Google Scholar 

  • Ghosh S, Günther A, Carranza EJM, van Westen CJ, Jetten VG (2010) Rock slope instability assessment using spatially distributed structural orientation data in Darjeeling Himalaya (India). Earth Surf Process Landf 35:1773–1792

    Article  Google Scholar 

  • Ghosh S, van Westen CJ, Carranza EJM, Jetten VG, Cardinali M, Rossi M, Guzzetti F (2012) Generating event-based landslide maps in a data-scarce Himalayan environment for estimating temporal and magnitude probabilities. Eng Geol 128:49–62

    Article  Google Scholar 

  • Goodman RE, Bray JW (1976) Toppling of rock slopes. In: Proceedings of speciality conference on rock engineering for foundations and slopes. American Society of Civil Engineers (ASCE), Boulder, CO

  • Günther A (2003) SLOPEMAP: programs for automated mapping of geometrical and kinematical properties of hard rock hill slopes. Comput Geosci 29:865–875

    Article  Google Scholar 

  • Günther A, Wienhöfer J, Konietzky H (2012) Automated mapping of rock slope geometry, kinematics and stability with RSS–GIS. Nat Hazards 61(1):29–49

    Article  Google Scholar 

  • Hack R, Price D, Rengers N (2003) A new approach to rock slope stability—a probability classification (SSPC). Bull Eng Geol Environ 62(2):167–184

    Google Scholar 

  • Hoek E, Bray JW (eds) (1981) Rock slope engineering. The Institution of Mining and Metallurgy, London

  • Jaboyedoff M, Baillifard F, Philippossian F, Rouiller JD (2004) Assessing fracture occurrence using “weighted fracturing density”: a step towards estimating rock instability hazard. Nat Hazards Earth Syst Sci 4:83–93

    Article  Google Scholar 

  • Meentemeyer RK, Moody A (2000) Automated mapping of conformity between topographic and geological surfaces. Comput Geosci 26:815–829

    Article  Google Scholar 

  • Palmstrom A (1982) The volumetric joint count—a useful and simple measure of the degree of jointing. IVth international congress IAEG, New Delhi, pp V221–V228

  • Parvaiz I, Champatiray PK, Bhat FA, Dadhwal VK (2011) Earthquake-induced landslide dam in the Kashmir Himalayas. Int J Remote Sens 33(2):655–660

    Article  Google Scholar 

  • Romana M (1985) New adjustment rating for application of the Bieniawski classification to slopes. In: Proceedings of the International Symposium on Rock Mechanics and Mining and Civil Works, ISRM, Zacatecas, Mexico, pp 59–63

  • Selby MJ (1993) Hillslope materials and processes. Oxford University Press, Oxford

    Google Scholar 

  • Singh B, Goel RK (2011) Chapter 18-slope mass rating, engineering rock mass classification. Butterworth-Heinemann, Boston, pp 231–243

  • Sinha-Roy S (1982) Himalayan main central thrust and its implications for Himalayan inverted metamorphism. Tectonophysics 84(2–4):197–224

    Article  Google Scholar 

  • Soja R, Starkel L (2007) Extreme rainfalls in Eastern Himalaya and southern slope of Meghalaya Plateau and their geomorphologic impacts. Geomorphology 84(3–4):170–180

    Article  Google Scholar 

Download references

Acknowledgments

The work presented here is part of the site-specific landslide investigation carried out by the Geological Survey of India (GSI) as per the approved annual programme of 2010–2012. The authors are grateful to the Border Roads Organisation, Government of India, for providing the necessary logistics in the field. The authors also sincerely acknowledge the support provided by Deputy Director General, GSI, Eastern Region and the Director General, GSI and for allowing us to publish this work. The authors are indebted to all the reviewers and the Editor of the journal for making a very comprehensive review of the manuscript, which substantially improved the quality of this paper.

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Correspondence to Saibal Ghosh.

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Ghosh, S., Kumar, A. & Bora, A. Analyzing the stability of a failing rock slope for suggesting suitable mitigation measure: a case study from the Theng rockslide, Sikkim Himalayas, India. Bull Eng Geol Environ 73, 931–945 (2014). https://doi.org/10.1007/s10064-014-0586-8

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