The 1999 edition of IS 14680 offers detailed procedures for assessing, preventing, and managing landslides in mountainous regions. It encompasses landslide classifications, investigative techniques, and various stabilization solutions such as slope reinforcement, retaining structures, excavation strategies, drainage, and erosion prevention. This code is indispensable for engineers and planners engaged in infrastructure and development projects in hilly terrains to effectively mitigate landslide hazards.
Overview
The 1999 edition of IS 14680 offers detailed procedures for assessing, preventing, and managing landslides in mountainous regions. It encompasses landslide classifications, investigative techniques, and various stabilization solutions such as slope reinforcement, retaining structures, excavation strategies, drainage, and erosion prevention. This code is indispensable for engineers and planners engaged in infrastructure and development projects in hilly terrains to effectively mitigate landslide hazards.
Audience
Contents
Structure
This section outlines the extent and major provisions of IS 14680, focusing on landslide risk identification, classification, site assessment, and stabilization measures. It covers diverse landslide types, investigation methods including static and dynamic cone penetration testing, and provides a systematic approach for selecting control methods based on landslide characteristics.
IS 14680 incorporates essential Indian Standards such as IS 1498 for soil classification, IS 1892 for foundation subsurface investigations, and IS 14458 (Part 2) for retaining wall design in hill areas. These references ensure a comprehensive framework for landslide control implementation.
Defines key terms used throughout the standard related to hill area development and landslide engineering. It elaborates on soil properties including index parameters, shear strength, and compressibility as per IS 1498, ensuring consistent interpretation for geotechnical assessments.
Presents a detailed categorization of landslide movements such as falls, topples, slides, lateral spreads, flows, and complex types. Each type is described along with material specifics and recommended stabilization practices to facilitate targeted intervention.
Details methodologies for subsurface exploration, emphasizing the use of static and dynamic cone penetration tests to delineate soil profiles up to failure surfaces or bedrock. This section guides the determination of borehole locations and sampling strategies essential for design.
Focuses on both direct and indirect interventions for landslide prevention. Direct methods include restraining walls, soil excavation, reinforced earth reconstruction, and rock reinforcement, while indirect approaches cover erosion control and enhanced drainage systems.
Explores physical stabilization techniques such as retaining and anchored walls, slope excavation, reinforced earth structures, and rock bolting. It discusses design criteria, construction considerations, and the importance of geotechnical data from referenced IS codes.
Describes the purpose, types, and design principles of restraining structures including rigid retaining walls and temporary solutions like interconnected bitumen drums. Stability checks for sliding and overturning are explained alongside relevant formulas and construction practices.
Outlines excavation methods such as removal of unstable soil, slope flattening, benching with drainage provisions, and realignment of slope profiles. The effect of these approaches on reducing driving forces and enhancing stability is highlighted.
Details the use of granular backfill combined with metallic or geosynthetic reinforcements and precast concrete facings to construct gravity retaining structures. Stability assessments for overturning, sliding, and shear failure are included with design parameters.
Focuses on stabilizing rock slopes through rock bolts, anchors, and mesh applications. Design considerations include rock mass evaluation, bolt sizing, spacing, grouting, and tensioning to secure unstable rock masses effectively.
Covers slope preparation, vegetation planting, application of asphalt emulsion mulch, and installation of jute or coir netting to prevent soil loss. The section also discusses bench terracing and surface water management practices to reduce erosion risks.
Describes construction and placement of catch water drains, roadside drains, and cross drains with specified gradients and spacing to intercept and divert runoff. Emphasis is placed on lining, velocity control, and maintenance to protect slopes from water-induced erosion.
Explains the installation of horizontal drains using perforated PVC pipes at negative gradients and deep trench drains filled with graded gravel wrapped in geotextile fabric. These systems are designed to lower pore water pressure and improve slope stability.
Provides guidelines on equipment essential for slope stabilization works including specifications for geotextile overlapping, gravel and boulder gradation in trench drains, and typical dimensions for drainage structures to ensure effective filtration and drainage in difficult terrains.
Frequently Asked
IS 14680 recommends different retaining wall constructions based on slope height: For slopes up to 3 meters, random rubble dry stone masonry walls are suitable due to their simplicity. For heights ranging from above 3 meters to 4 meters, banded mortar masonry walls with lime or cement mortar bands spaced at 3-meter intervals are advised, featuring a 0.6 m top width and a front batter of 1:3. For slopes exceeding 4 meters or those requiring increased stability, concrete gravity retaining walls are preferred, which necessitate foundations on bedrock or stable soil beneath the slip surface, and include design considerations for stem strength, drainage (weep holes), and protection against scour or frost, following IS 14458 (Part 2).
Soil nailing enhances slope stability by inserting steel rods or bars into predrilled holes within the soil mass, which resist tensile, compressive, shear, and bending forces. Combined with a shotcrete facing panel, this forms a composite structure that binds the soil, particularly effective for near-vertical slopes and compact granular soils. This technique provides a cost-efficient and tidy solution to stabilize slopes and excavations without extensive earthworks.
Effective excavation methods include removing unstable soil or debris to reduce sliding mass, flattening slopes to lessen shear stresses, benching by creating stepped terraces that reduce runoff velocity and slope length, altering line or grade to bypass unstable zones, and modifying slope geometry for improved stability. These methods are often complemented with subsurface drainage systems like horizontal drains to lower pore water pressure.
IS 14680 advises sub-surface drainage techniques such as horizontal drains using 50 mm diameter perforated PVC pipes installed at a negative slope of 5° to 15°, equipped with check valves and wrapped in geotextile to prevent clogging. Deep trench drains filled with graded gravel wrapped in filter fabric are also recommended for depths up to 8 meters. These methods effectively lower pore water pressure, enhancing slope stability.
Erosion control involves preparing the slope by grading and raking topsoil approximately 20 mm thick, followed by seeding or planting root slips spaced 150-200 mm apart. Applying an asphalt emulsion mulch at 0.9 liters per square meter forms a protective film aiding seed germination. Additionally, coir or jute netting can be laid over seeded slopes, anchored with 150 mm iron nails, acting as check dams to reduce soil loss and nutrient depletion, thereby promoting rapid vegetation establishment and soil stabilization.
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