Question

Cantilever retaining walls can safely be used for a height not more than:

• A. \( 2 \, \text{m} \)
• B. \( 4 \, \text{m} \)
• C. \( 5 \, \text{m} \)
• D. \( 6 \, \text{m} \)

Hint:

Use cantilever retaining walls for heights up to 6 m. Beyond this, lateral pressure increases rapidly, making counterfort walls a more efficient and safer option.

Answer 1

The Correct Option is D

Step 1: Understand the components of a cantilever retaining wall.
A cantilever retaining wall is a reinforced concrete wall that retains earth without external bracing. It consists of the following key components:

• Vertical stem (retains the soil)
• Base slab, which includes:
  • Heel (part of the base under the backfill)
  • Toe (part of the base in front of the wall)

Step 2: Structural behavior and design.
The wall acts as a cantilever fixed at the base. The pressure exerted by the retained soil increases with height and acts laterally on the vertical stem. The stem, heel, and toe are designed for bending, shear, and overturning.
Step 3: Practical and economic height limit.
According to IS 456 and standard design practices in structural engineering:
Cantilever retaining walls are economical and stable up to a height of about \( 6 \, \text{m} \).
For heights beyond \( 6 \, \text{m} \), counterfort retaining walls are preferred because they reduce the bending moments and material consumption by introducing triangular counterforts that tie the wall and base slab together.
Step 4: Conclusion.
Thus, from both economic and structural stability viewpoints, the maximum safe height for a cantilever retaining wall is: \[ \boxed{6 \, \text{m}} \]