Stabilization of Cut Slopes along the Highway by Optimizing Geometry, NH-58, Lesser Himalaya

Abstract

The Himalayan ranges are well known for active and incessant slope failures. The network of highways and local roads in the region is under sustained threat of potential fatal landslides. Urban sprawl and increased human intervention increased the vulnerability and probability of sliding to manifolds. Tampering the fragile conditions of the sensitive Himalayan orogen may generate new avenues of slope failures. Road widening and development projects have a close association with slope failures. However, such landslides can be coped with proper geotechnical planning and execution. The slopes along national highway-58 (NH-58) are being excavated for road widening. Large numbers of steep and unstable cut sections were visible soon after the excavation along the highway. The geotechnical assessment has been undertaken to determine stable slope geometry. The profile of existing slopes is modified by creating benches, and safety factor was determined at different overall angle. The optimization of slope geometry suggests that most of the unstable slope may have safety factor of 1.5, by creating benches of 10 m (height), 5 m (span), at an angle of 65°. It can also be inferred from the analysis that the safety factor may be improved from 11.5 to 32.2% for each 5° reduction in the overall slope angle. Certain adverse impacts and future projections of inadequately performed road widening were also discussed in the paper.