Retaining and breast walls — purpose of providing weep holes Why are weep holes provided through retaining/breast walls (with proper filters) toward the exposed face?

Introduction / Context:
Backfill behind retaining walls can become saturated due to rainfall and seepage. Water adds hydrostatic pressure and reduces the effective stress and shear strength of the soil, threatening wall stability. Weep holes provide a pressure-relief path for water to escape safely through the wall.

Given Data / Assumptions:

• Gravity or RC cantilever retaining/breast walls.
• Free-draining layer or geotextile/filter behind the wall.
• Proper spacing and invert level near the base.

Concept / Approach:

Weep holes work with drainage blankets or pipes to dissipate pore pressures. Their placement is typically near the toe region where water accumulates. Filters prevent soil piping and loss of fines. With water pressures relieved, sliding, overturning, and bearing checks are less critical and more economical sections are achievable.

Step-by-Step Solution:

Verification / Alternative check:

Standard details place weep holes with graded filters or geotextiles and often include a perforated collector pipe to direct flows to outlets.

Why Other Options Are Wrong:

• (b) No need for “ventilation” through structural walls; airflow is not the purpose.
• (c) Aesthetic perforations are not sound engineering.
• (d) Weep holes do not reduce earth mass weight in any meaningful way.
• (e) They do not increase compaction; they drain water.

Common Pitfalls:

• Omitting filters, causing soil piping and staining.
• Placing weep holes too high, leaving pore water trapped at the base.

Final Answer:

To drain off water from the backfill and relieve hydrostatic pressure.