Retaining Walls For Slopes and Embankments
Gravity Retaining Walls
A gravity retaining wall is a rigid structure built to retain soil by using its own weight to resist lateral earth pressure. The wall is designed to be thick and massive, so the downward force due to gravity provides stability against sliding, overturning, and bearing failure.
These walls are usually constructed from stone masonry, brick masonry, or plain/mass concrete. Their cross-section is wider at the base and gradually reduces toward the top, which helps improve stability. Since no steel reinforcement is used, gravity retaining walls have a simple design and construction process.
Drainage systems such as weep holes are provided to prevent the buildup of water pressure behind the wall. Gravity retaining walls are most economical for low to medium heights, typically up to 3–4 meters, and are commonly used in road embankments, hill areas, landscaping, and building foundations.
In summary, gravity retaining walls are preferred where simplicity, durability, and low maintenance are required, and where sufficient space is available for a wide base.
Cantilever Retaining Walls
A cantilever retaining wall is a reinforced concrete structure that resists lateral earth pressure by cantilever action of its components rather than by self-weight alone. It consists of a thin vertical stem and a base slab, which is divided into a heel slab (under the backfill) and a toe slab (in front of the wall).
The wall stem and base slab act as cantilever beams, fixed at the base, and transfer the earth pressure safely to the foundation soil. The weight of the soil resting on the heel slab helps improve stability
Counterfort Retaining Walls
A counterfort retaining wall is a type of reinforced concrete retaining wall used for large heights, in which triangular vertical slabs called counterforts are provided at regular intervals on the back (soil) side of the wall. These counterforts connect the wall stem and the base slab, reducing bending moments and shear forces.
Mechanically Stabilized Earth (MSE) Walls
A Mechanically Stabilized Earth (MSE) wall is a reinforced soil retaining structure in which the stability of the soil mass is improved by the inclusion of reinforcing elements. These elements are typically metal strips, steel bars, geogrids, or geotextiles placed in horizontal layers within the backfill and connected to a facing panel.
Gabion Retaining Walls
A gabion retaining wall is a flexible retaining structure constructed using wire mesh baskets (gabions) filled with stones or rock fragments. These walls rely on the weight of the stones and the interlocking action of the rocks to resist lateral earth pressure.
Gabion walls are permeable, allowing water to drain through the structure, which reduces hydrostatic pressure behind the wall. They are particularly effective in erosion control, riverbank stabilization, and slope protection.
The walls are typically built in tiers or stepped arrangements, and the baskets are stacked and tied together with wire to maintain stability. The flexibility of gabion walls allows them to adjust to minor ground movements without cracking, making them suitable for unstable or soft soils.
Earth Pressure Considerations
The design of retaining walls primarily depends on lateral earth pressure exerted by the retained soil. Depending on wall movement and soil condition, earth pressure is classified as: stabilization, and slope protection.
- Active earth pressure – when the wall moves away from the backfill.
- Passive earth pressure – when the wall moves toward the soil.
- At-rest earth pressure – when wall movement is restrained.