Geotextiles for Slope Stabilization

Slopes fail when the forces pushing soil downhill exceed the soil’s strength. Deforestation, rapid urbanization and road cutting in hill areas have made slope failures more frequent, and they cause environmental, economic and human losses. Some failures are sudden, such as a slide after heavy rain; others are slow, such as creep or gradual erosion of a cut face. Ocean Geotextiles and related geosynthetics are used to stabilize both kinds. This post explains how.

What are slopes?

Slopes are mostly natural features, but they are also part of human-made structures such as highways, dams and canals. Many roads run along or cut into hillsides, and civil engineering and mining projects create new slopes through excavation and fill.

What leads to instability of slopes?

A slope becomes unstable when soil starts to move and takes structures with it. Stabilization starts with knowing the cause. Common causes are erosion, rainfall, earthquakes, external loading, construction activities, rapid drawdown (a fast drop in water level next to a slope, as in a reservoir or canal) and geological features such as weak layers or adverse joints.

Solution: Ocean Geotextiles for slope stabilization

Geosynthetics have made it quicker and cheaper to stabilize steep slopes and embankments than with heavy concrete or stone works alone.

The right solution depends on the slope gradient, the purpose of stabilization, the time available, site access, the cost of repair and the construction equipment available. The common techniques are geometric (regrading or benching the slope), hydrological (drainage to lower groundwater and pore pressure), and chemical and mechanical methods.

Chemical and mechanical techniques increase the shear strength of the soil or rock mass, or reduce the external forces that trigger failure.

Geotextiles are flexible, strong in tension and highly permeable, so on slopes they are used as filters behind drains, as separators under stone or gabion facings, and as reinforcement in steep reinforced-soil slopes. On the slope surface, erosion control mats and coir geotextiles hold soil and seed in place until vegetation establishes, as in Ocean’s slope stabilization project in Kullu.

The Ocean Geonet is made of extruded HDPE and is used for drainage. It can be combined with geotextile fabrics, bonded to one or both faces, to form a drainage geocomposite.

How does Ocean Geonet help slope stabilization?

Water is behind most slope failures, so drainage is one of the most effective stabilization measures. A geonet or geonet-geotextile composite laid on the slope under a cover soil, or behind a retaining wall, carries seepage water along its plane to an outlet. That keeps pore-water pressure down in the cover soil and the slope behind it, which preserves the soil’s shear strength. It also stops cover soils on lined slopes sliding off when they become saturated.

UV Resistance: HDPE geonets contain carbon black and stabilizers that slow degradation from sunlight, so they suit long-term applications. They should still be covered after installation where the design allows.

Chemically Inert: HDPE resists acidic and alkaline soils and groundwater with no meaningful loss of strength.

Biological Resistance: HDPE is not attacked by microorganisms, which helps it last for the life of the slope.

For surface erosion on the slope face, combine the drainage layer with an erosion control mat or coir geotextile. The mat slows surface runoff, protects the soil from raindrop impact, and gives roots support and moisture while vegetation establishes. These measures are usually quicker to install and cheaper than concrete or stone pitching.

Ocean Non Woven Geosynthetics supplies a range of geosynthetics products and materials in different configurations and strengths for erosion control and slope stability. Contact us to discuss your slope.