Short note: breast wall

A breast wall is a wall built on the hill side of a hill road, against a cut slope, to support the slope face and prevent small slips, rock fall, and weathering or erosion of the cut face. It is not intended to resist the full thrust of a retained mass of fill, but to stabilise the cut face and the slope material above it (IRC:SP:48).

Features

• Constructed in stone masonry (dry or in cement/lime mortar), plain/reinforced concrete or gabion; the wall rests on firm rock or soil.
• Height typically 3-5 m; if the cut is higher, the wall is built in tiers with berms.
• Weep holes (75-100 mm, at about 2-3 m spacing) and a filter/drainage layer behind it release the pore water pressure.
• The back face is kept very close to the cut slope (front face batter about 1 in 4 to 1 in 3); the space behind is filled with the excavated material or packed with stones.
• The top of the wall is connected to the drainage system, and the side drain runs along its base; the top of the cut above is protected by a catch drain and vegetation.

   hill slope  \
                \ cut face
                 |#| breast wall
                 |#|  weep holes
   ==============|#|===  road

Functions

• Supports the hillside cut, preventing slides.
• Protects against erosion and weathering.
• Reduces the width needed for cut slopes, saving land and excavation.

On the valley side, a retaining wall is used instead.