Correct Answer - Option 4 : Hair-pin bends
Explanation:
Hair-pin bends:
(i) A hairpin turn or hairpin corner is a bend in a road with a very acute inner angle, making it necessary for an oncoming vehicle to turn almost 180˚ to continue on the road. This does not help during landslides in any way.
Retaining walls:
(i) The walls constructed for retaining or supporting earth against their back are called retaining walls. Earth cannot remain vertical but would be in a state of equilibrium when it assumes a natural angle which is called the angle of repose.
(iii) If it is desired to retain the earth vertically, that portion of the earth will have to be supported by a wall called a retaining wall.
(iii) Retaining walls are used to retain soil mass on one side of the road, hence during landslides to control the flow of soil mass.
Breast wall:
(i) A breast wall is constructed to protect the natural sloping ground from the cutting action of natural agents. Breast walls also prevent slides of unreliable soils.
(ii) The breast walls may be 0’6 m wide at the top. Weep holes should be provided at regular intervals among the length of the wall to relieve the walls of saturated earth pressure.
(iii) The breast wells are so designed that their line of pressure should be normal to the earth's pressure or thrust.
Catch water drain:
(i) A surface drain to intercept and collect the flow of water from adjoining land, so as to prevent it from reaching a road or mine sidings.
