Hill road structures: The wall provided on the valley (downhill) side to stabilize and retain the backfilled portion of the roadway embankment is called what?

Introduction / Context:
In hill road construction, cut and fill operations require support structures to ensure long-term stability. Different walls serve distinct purposes depending on whether the road is cut into the hillside or supported on an embankment on the valley side.

Given Data / Assumptions:

• Roadway on a hillside with a backfilled embankment on the valley side.
• Wall function: retain soil and prevent outward movement/failure.

Concept / Approach:

A retaining wall is constructed to hold back soil or fill material—typically on the valley side where the embankment needs lateral support. A breast wall is usually provided on the hill (cut) side to stabilize the natural slope and prevent slips. A parapet wall is a safety barrier at the edge and does not retain earth.

Step-by-Step Reasoning:

Verification / Alternative check:

Hill road manuals consistently distinguish retaining vs. breast walls by location and purpose; design depends on earth pressure, drainage, and foundation conditions.

Why Other Options Are Wrong:

• Breast wall: used on hill side for cut stabilization, not for retaining valley embankment fill.
• Parapet wall: provides edge protection but not earth retention.
• “All the above”: combines dissimilar functions incorrectly.

Common Pitfalls:

• Using parapet walls as structural retainers (unsafe).
• Confusing cut-slope stabilization (breast wall) with fill retention (retaining wall).

Final Answer:

Retaining wall.