What is the Stability of Different Types of Retaining Walls?
Figure 1 shows gravity, cantilever, and counterfort types of retaining walls.
The stability of a gravity wall is due to the self-weight of the wall and the passive resistance developed in front of the wall. The gravity walls are designed using Coulomb’s theory. Reinforced concrete walls (cantilever or counter-fort types) are more economical than gravity walls because the backfill itself provides most of the required dead load. Rankine’s theory is used to investigate the stability of reinforced concrete walls.
The factor of Safety – For stability, a retaining wall should satisfy the following conditions.
- The wall should be stable against sliding. The factor of safety against sliding shall be a minimum of 1.5.
- The Wall should be stable against overturning. For granular backfill, the factor of safety against overturning shall be a minimum of 1.5. For cohesive backfill, the factor of safety against overturning shall be a minimum of 2.
- The base of the wall should be stable against bearing capacity failure. For granular backfill, the factor of safety against bearing capacity failure shall be a minimum of 2. For cohesive backfill, the factor of safety against bearing capacity failure shall be a minimum of 3.
- The resultant of all the forces should fall within the middle third of the base.