IRC Code: SP:106-2015 - Engineering Guidelines on Landslide Mitigation Measures for Indian Roads

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Landslides pose a significant threat to road infrastructure, particularly in hilly and mountainous terrains. The IRC Code: SP:106-2015 provides a comprehensive framework for landslide hazard assessment, monitoring, and mitigation measures to ensure safer and more sustainable road networks in India. This guideline, published by the Indian Roads Congress (IRC), serves as a vital reference for civil engineers, policymakers, and infrastructure developers.

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In this blog, we will explore the key aspects of the IRC: SP:106-2015, including landslide classification, hazard mapping, risk assessment, early warning systems, and modern stabilization techniques.

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Understanding Landslides and Their Impact on Indian Roads

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Landslides are mass movements of rock, soil, and debris down slopes due to factors like heavy rainfall, earthquakes, deforestation, and improper construction practices. These events can damage roads, disrupt transportation, and endanger human lives. The increasing frequency of landslides along Indian highways highlights the need for effective mitigation strategies.

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1. Landslide Hazard Mapping and Risk Assessment

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The first step in mitigating landslides is hazard mapping. The IRC: SP:106-2015 outlines the following key methodologies:

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• Susceptibility Mapping – Identifies areas prone to landslides based on historical data and terrain analysis.
• Hazard Mapping – Estimates the probability of failure and categorizes risk levels.
• Risk Mapping – Assesses infrastructure vulnerability and potential economic losses​.

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The document recommends different scales for landslide zoning:ScaleApplication1:50,000 - 1:100,000Regional planning & policy decisions1:25,000 - 1:50,000Preliminary hazard mapping for local projects1:5,000 - 1:25,000Advanced planning for roads & railways1:500 - 1:5,000Site-specific hazard & risk zoning2. Monitoring Landslides: Early Warning SystemsOne of the major highlights of IRC: SP:106-2015 is its emphasis on early warning systems (EWS). These systems help predict landslide occurrences using surface and subsurface monitoring techniques:

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• Surface Monitoring – Involves GPS surveys, geodetic techniques, and aerial photogrammetry to detect ground movement.
• Subsurface Monitoring – Uses inclinometers, extensometers, and piezometers to measure internal slope stability.
• Remote Sensing & SAR Technology – Earth observation satellites like Radarsat, TerraSAR-X, and ALOS are used to detect terrain deformations​.

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A well-implemented EWS can reduce loss of life and property damage by issuing timely warnings.3. Landslide Mitigation Techniques for RoadsThe IRC: SP:106-2015 suggests a multi-pronged approach to stabilizing slopes and preventing landslides. These include:A. Drainage Control MeasuresProper drainage design plays a crucial role in slope stability. The guidelines suggest:

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• Surface Drainage – Installing channels, culverts, and catchment drains to divert rainwater.
• Subsurface Drainage – Using French drains, horizontal drains, and geosynthetic filters to control groundwater flow.

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B. Structural Measures

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• Retaining Walls – Concrete, masonry, or geogrid-reinforced structures prevent slope failures.
• Soil Nailing & Rock Anchors – Provide additional support to unstable slopes.
• Gabion Walls – Flexible rock-filled wire mesh structures that absorb impact forces​.

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C. Bio-Engineering & Slope Stabilization

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• Revegetation – Planting deep-rooted vegetation to bind soil.
• Terracing & Benching – Creating steps along slopes to reduce erosion.
• Geosynthetics & Reinforced Earth – Using geotextiles and geogrids to improve soil strength​.

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4. Post-Disaster Management Strategies

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‍The IRC: SP:106-2015 also provides guidelines for handling landslides after they occur:

• Clearing debris and restoring road connectivity.
• Conducting geotechnical investigations to assess stability.
• Implementing long-term rehabilitation measures, such as slope reengineering and hazard mitigation planning​.

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Conclusion

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‍The IRC Code: SP:106-2015 serves as an essential guide for engineers and policymakers working on road infrastructure in landslide-prone regions. By incorporating advanced monitoring technologies, effective drainage solutions, and slope stabilization techniques, we can ensure safer and more resilient roads.

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