IRC:SP:106-2015 ENGINEERING GUIDELINES ON LANDSLIDE MITIGATION MEASURES FOR INDIAN ROADS Published by: INDIAN ROADS CONGRESS Kama Koti Marg, Sector-6, R.K. Puram, New Delhi-110 022 January, 2015 Price : ` 800/- (Plus Packing & Postage) IRC:SP:106-2015 First Published : January, 2015 (All Rights Reserved. No part of this publication shall be reproduced, translated or transmitted in any form or by any means without the permission of the Indian Roads Congress) Printed by India Offset Press, Delhi-110 064 1000 Copies b IRC:SP:106-2015 CONTENTS S. No. Description Page No. Personnel of the General Specifications and Standards Committee i-ii Definition 1 Introduction 6 1. Overview of Landslided Hazards In India 8 2. Landslide Features and Geometry 11 3. Classification 16 4. Landslide Hazard Mapping, Vulnerability and Risk Assessment 23 5. Methods of Scientific Investigation of Slopes and Landslides 37 6. Instrumentation, Monitoring, Forecasting and Early Warning of 43 Landslides 7 Landslide Risk Reduction through Improved Planning, Design and 58 Construction Practices 8. Technology for Landslide Prevention and Remediation 72 9. References 87 Annexure 1 100 IRC:SP:106-2015 PERSONNEL OF ThE GENERAL SPECIFICATIONS AND STANDARDS COMMITTEE (As on 8th August, 2014) 1. Das, S.N. Director General (Road Development), Ministry of Road (Convenor) Transport & Highways, New Delhi 2. Varkeyachan, K.C. Addl. Director General, Ministry of Road Transport & (Co-Convenor) Highways, New Delhi 3. Chief Engineer (R) S, R & T (Rep. by Shri S.K. Nirmal), Ministry of Road Transport & (Member Secretary) Highways, New Delhi Members 4. Dhodapkar, A.N Chief Engineer (Retd.), MORTH, New Delhi 5. Datta, P.K. Director-Corporate Development, M/s Trans Asia Infrastructure Pvt. Ltd., New Delhi 6. De, D.C. Executive Director, Consulting Engineering Services (India) Pvt. Ltd. New Delhi 7. Duhsaka, Vanlal Chief Engineer, PWD Highways, Aizwal 8. Joshi, L.K. Former Secretary, Ministry of Road Transport & Highways, New Delhi 9. Kadiyali, Dr. L.R. Chief Executive, L.R. Kadiyali & Associates, New Delhi 10. Kumar, Ashok Chief Engineer (Retd.), Ministry of Road Transport & Highways, New Delhi 11. Kumar, Dr. Kishor Chief Scientist , Geotechnical Engineering Division, CRRI, New Delhi 12. Mandpe, P.S. Chief Engineer (NH), PWD Maharashtra 13. Narain, A.D. Director General (RD) & AS (Retd.), MOST, Noida 14. Pandey, I.K. Chief General Manager (Tech.), National Highways Authority of India, New Delhi 15. Patwardhan, S.V. Advisor, Madhucon Projects Limited, New Delhi 16. Puri, S.K. Director General (RD) & Spl. Secretary, MoRT&H (Retd.), New Delhi 17. Rajoria, K.B. Engineer-in-Chief (Retd.), Delhi PWD, New Delhi 18. Rao, P.R. Vice President, Soma Enterprises Ltd., Gurgaon 19. Raju, Dr. G.V.S. Engineer-in-Chief (R&B), Admn. & National Highways, Hyderabad, Andhra Pradesh 20. Selot, Anand Former Engineer-in-Chief, PWD Madhya Pradesh 21. Sharma, D.C. Sr. Principal Scientist and Head Instrumentation Division, CRRI, New Delhi i IRC:SP:106-2015 22. Sharma, D.D. Chairman, M/s D2S Infrastructure Pvt. Ltd, New Delhi 23. Sharma, Rama Shankar Chief Engineer (Retd.), MoRT&H, New Delhi 24. Sharma, S.C. Director General (RD) & AS (Retd.), MOST, New Delhi 25. Shrivastava, Palash Director, IDFC, New Delhi 26. Singh, NirmalJit Director General (RD) & Spl. Secretary, MoRT&H (Retd.), New Delhi 27. Sinha, A.V. Director General (RD) & Spl. Secretary, MoRT&H (Retd.), New Delhi 28. Sinha, N.K. Director General (RD) & Spl. Secretary, MoRT&H (Retd.), New Delhi 29. Tamhankar, Dr. M.G. Director-Grade Scientist (SERC-G) (Retd.), Navi Mumbai 30. Tandon, Prof. Mahesh Managing Director, Tandon Consultants Pvt. Ltd. 31. Vasava, S.B Chief Engineer & Addl. Secretary (Panchayat), Roads &Building Deptt. Gandhinagar, Gujarat 32. Velayutham, V. Director General (RD) & Spl. Secretary, MoRT&H (Retd.), New Delhi 33. Verma, Maj. V.C. Director, Marketing, Oriental Structural Engineers Pvt. Ltd., New Delhi 34. Rep. of NRRDA (Pateriya, Dr. I.K.) Director (Technical ), NRRDA NBCC Tower, Bhikaji Cama Place, New Delhi 35. The Dy. Director General (Lal, B.B.) Chief Engineer, DDG D&S Dte. Seema Sadak Bhawan, New Delhi 36. The Chief Engineer (NH) PWD, Jaipur (Rajasthan) 37. Rep. Chief Engineer (Basu, Kaushik) Chief Engineer (Mechanical), (Mechanical), MORTH MoRTH, New Delhi Ex-Officio Members 1. President, (Bhowmik, Sunil), Engineer-in-Chief, Indian Roads Congress PWD (R&B), Govt. of Tripura 2. Honorary Treasurer, (Das, S.N.), Director General (Road Development), Indian Roads Congress Ministry of Road Transport & Highways 3. Secretary General, Sajjan Singh Nahar Indian Roads Congress ii IRC:SP:106-2015 ENGINEERING GUIDELINES ON LANDSLIDE MITIGATION MEASURES FOR INDIAN ROADS DEFINITION Abandoned: Inactive landslide no longer affected by its original causes. Acceptable Risk – A risk for which, for the purposes of life or work, we are prepared to accept as it is with no regard to its management. Society does not generally consider expenditure in further reducing such risks justifiable. Accumulated Mass; Accumulation: Volume of displaced material that lies above the original ground surface of a landslide. Active: Landslide that is currently moving, first-time movement or reactivated. Activity: Stage of development of a landslide, including the state of activity, distribution of activity, and style of activity. Advancing: Activity the rupture surface extends in the direction of movement. ALARP: As Low as Reasonably Practicable; with reference to risk. Analysis: Process to determine the nature and level of hazard and risk; typically includes scope definition, identification and estimation. Annual Exceedance Probability (AEP) – The estimated probability that an event of specified magnitude will be exceeded in any year.s Assessment: Overall process of hazard or risk identification, analysis and evaluation. Complex: Activity where a landslide exhibits at least two types of movement (fall, topple, slide, spread, or flow) in sequence. Composite: Activity where a landslide exhibits at least two types of movement (fall, topple, slide, spread, or flow) in different parts of the displaced mass at the same time. Confining: Activity where there is a scarp but no rupture surface visible at the foot of the displaced mass. Consequence: Probability of total loss or damage, or a proportion of loss or damage, to an element at risk; combination of spatial probability, temporal probability and vulnerability. Control: Process of decision making for managing hazard or risk, and implementation or enforcement of hazard or risk mitigation measures and re-evaluation of the effectiveness from time to time, using the results of hazard of risk assessment as one input. Criteria: Terms of reference against which the significance of a hazard or risk are evaluated. 1 IRC:SP:106-2015 Danger (Threat): Natural phenomenon that could lead to loss, disadvantage, damage, injury or loss of life; does not include any forecasting; also see Hazard. Disaster: A serious disruption of the functioning of society, causing widespread human, material or environmental losses, which exceed the ability of affected society to cope using only its own resources. Dormant: Inactive landslide that can be reactivated by its original or other causes. Early Warning: Provision of timely and effective information, through identified institutions, that allows individuals exposed to a hazard to take action to avoid or reduce their risk and prepare for effective response. Elements at Risk: population, buildings and engineering works, economic activities, public utilities, other infrastructure, and environmental values in an area affected, or potentially affected by a landslide. Enlarging: Activity where the rupture surface of a landslide is extending in two or more directions. Erosion: Process of weathering and transport of soil and rock from their natural environment or source. Agents of erosion include wind, water, ice, gravity and living organisms (bioerosion). Estimation: The determination of hazard or risk. Evaluation: Using values and judgments in the decision process, either explicitly or implicitly, to determine the importance of the estimated hazard or risks, and there by identify alternatives to manage the hazards or risks. Event: Occurrence or change of a particular set of circumstances; a landslide is an example of an event. Frequency: Probability or likelihood of occurrence of a repeating event, such as a landslide, expressed as the number of occurrences per unit time; also a measure of past occurrences per unit time; also see Probability and Likelihood. hazard: Condition with the potential for causing an undesirable consequence; source of potential harm; also see Danger; or Inactive: Landslide that has not moved within the last 12 months; can be sub-divided into dormant, abandoned, stabilized, relict, and repaired. Individual Risk: Risk of the fatality or injury to an identifiable individual who lives or otherwise occupies an area affected, or potentially affected, by a landslide. Intensity: Set of spatially distributed parameters related to the destructive power of landslide; can be described quantitatively or qualitatively; can include maximum velocity, total displacement, differential displacement, depth of moving mass, peak discharge per unit width, kinetic energy per unit area. 2 IRC:SP:106-2015 Inventory: Study of the location, classification, volume, activity, date of occurrence and other characteristics of landslide within an area. Involuntary Risk: Risk that typically is imposed on an individual or society. Landslide: Down slope movement of a mass of soil (earth or debris) or rock down a slope. Level of hazard or Risk: Magnitude of a hazard or risk, expressed in terms of probability or likelihood (for hazard) and in terms of probability or likelihood and consequences (for risk). Likelihood: Chance of an event occurring; a qualitative description of probability of a landslide. Management: Process of hazard or risk assessment and control or treatment. Marginal: Inactive landslide, between preparatory and active, where a trigger can initiate movement. Mitigation: Strategy to reduce the effect of a landslide. Monitoring: Continual or frequent checking, critically observing or determining the status of activity of a landslide to identify change. Multiple: Activity where a landslide shows repeated development of the same type of movement. Partial Risk: Combination of the probability of a (hazardous) landslide and probability of the landslide affecting the site of an element at risk at the site when the landslide occurs; does not consider vulnerability; P(HA) = P(S:H) x P(T:S). Passive: From of mitigation that requires no design engineering; includes avoidance, land use regulations, education and warning systems. Preparatory: Inactive land area where destabilizing processes are insufficient to cause a landslide. Preparatory Causes: Reasons(s) that a landslide occurred at a particular location and time; mechanism(s) that put a landslide into a preparatory state of activity; can include geological factors (e.g. sensitive material, joints and fissures), geomorphological factors (e.g. slope angle, erosion), physical factors (e.g. rainfall, earthquake) and factors associated with human activity (e.g. addition of a load or excavation).s Probability: a) Estimate of the degree of certainty between 0 (impossible) and 1 (certain) of an event occurring; also see Likelihood and Frequency; can be statistical or subjective; or b) Probability of occurrence of a landslide; can be statistical or subjective; P(H). 3