9.6.1 Gravity Walls
A gravity wall is typically made of mortarless stone, masonry units or concrete and relies on its weight for stability (Figure 26 & 27). Gravity is able to hold back the earth or soil, due to its construction. For this purpose, the mass of the structure must be sufficient to develop enough frictional resistance to sliding, and the base or footing of the structure must be wide enough to develop sufficient moment to resist overturning earth forces.
The thickness of the wall at the base exceeds that at the top. Construction of gravity walls demands a high quantity of building materials. That is the reason why these walls are difficult to build and get more cumbersome as they get higher.
Today, taller retaining walls are increasingly built as composite gravity walls such as: geosynthetic or with precast facing; gabions (stacked steel wire baskets filled with rocks); crib walls (cells built up log cabin style from precast concrete or timber and filled with soil); or soil-nailed walls (soil reinforced in place with steel and concrete rods).
Figure 26: Gravity walls Made of Different Materials
Figure 27: Show force act on gravity wall.