Roadside structures and landslide stabilisation

Road-side structures for stability of the roadway

1. Retaining walls (masonry, gabion, RCC) on the valley side to hold fills.
2. Breast walls on the hill side to support cuts.
3. Drainage structures - catch water drains, side drains, culverts, chutes, French drains and horizontal drains to keep water out of the slope.
4. Toe walls, buttresses and parapets (guard walls) at the valley edge.
5. Rock-fall and slope protection - rock nets, shotcrete, catch ditches, turfing, stone pitching.
6. Gully control works - check dams, drop structures.
7. Bio-engineering works over the exposed slopes.
8. Berms and benches on high cuts.

Stabilising landslides along the road

First investigate: type of slide (rotational, translational, debris flow, rock-fall), cause (water, loading, toe cutting), extent, depth of slip plane, and monitor movement.

1. Drainage control (most effective) - divert surface water with catch drains and lined channels around the slide; remove subsurface water with horizontal drains, French drains, and cut-off trenches; seal cracks.
2. Geometric changes - unload the head (remove soil from the top), load the toe with a berm, flatten the slope, or construct benches.
3. Retaining structures at the toe - gabion/masonry walls, piles, anchors, and buttresses to resist the slide.
4. Soil reinforcement - soil nails, rock bolts, ground anchors, geogrids; grouting of fractured rock.
5. Bio-engineering - grasses, shrubs and trees to bind soil and absorb water, plus jute net, bamboo, and brush layering.
6. Realignment - if the slide is large, shift the road away or bridge over it; or use a bypass.
7. Maintenance - regular inspection, cleaning of drains and early repair after each monsoon.