Landslide Protection and Slope Protection With Gabion Retaining Wall

Landslides are the downward movement of rock, soil or both along hill and mountain slopes. In uninhabited places they are a hazard; in inhabited areas they become disasters. In India they are most common in the Himalayas of the north and north-east, the Western and Eastern Ghats, and the Vindhyan hills. Every monsoon, landslides kill people, destroy homes and cut roads and railways. Development activity, heavier rainfall events and other environmental factors are all adding to the risk.

Excavation, mining, cutting or loading slopes (for roads and buildings) and deforestation are the main human activities that destabilise hill slopes. A workable solution has to deal with slope failure, surface erosion, drainage and groundwater together. This post looks at landslide mitigation and slope protection with gabion retaining walls, often combined with erosion control mats on the slope face above the wall.

Ocean Geosynthetics supplies gabions for gabion retaining walls on slopes vulnerable to landslides.

How do landslides occur?

Most landslides in India are triggered by rain. Prolonged monsoon rain or a cloudburst (and occasionally a glacial lake outburst) saturates the soil, raises pore-water pressure and reduces the soil’s shear strength. Once the driving force on the slope exceeds its resistance, the mass slides, often turning into a debris flow that sweeps up everything in its path. Earthquakes, toe erosion by rivers and slope cutting are the other common triggers. Fragile hill areas need slope stabilization planned in advance, before a slide, not only repair afterwards.

Role of Gabion Retaining Walls in landslide protection

Any landslide-prone site needs a detailed investigation before a mitigation plan is drawn up: the stratigraphy, the soil and rock properties, groundwater levels and the forces destabilizing the slope. Gabion walls work well for shallow slides and for supporting the toe of a slope. Deep-seated slides usually also need subsurface drainage, soil nails, anchors or piles.

Mesh gabions used as a retaining wall are a low-cost form of landslide protection. They are assembled quickly, filled with stone from the site, and stay flexible: the wall can deform with ground movement without losing strength. They are also permeable, so water drains freely through the wall instead of building up pressure behind it.

A gabion retaining wall is a gravity structure: its weight resists the lateral earth pressure from the slope behind it and catches small debris falls. Gabion gravity walls are commonly built up to about 30 feet (roughly 9 m) high, usually stepped back in tiers. For an example, see Ocean’s gabion boxes for slope stability case study.

Why Gabions?

Gabions are durable and flexible, and the steel mesh gives the wall tensile strength that dry stone lacks. Galvanized (and optionally PVC-coated) wire resists corrosion. They are easy to transport to remote hill sites, quick to assemble at low cost, and follow uneven ground. With proper surface drainage above the wall to channel runoff away, gabion walls need little maintenance.

Ocean Geosynthetics supplies weld mesh gabions and double-twisted hexagonal gabions in various sizes, as gabion baskets, mattresses and decorative gabions. Where loose rock above a road or settlement is the main risk, gabions can be combined with rockfall protection. Contact us for details and to discuss your project.

FAQs