1 name the primary forces which must be considered when shor

Solution

Q.1.

While excavating trenches or similar shapes in soils, the safety of the workers is important, and therefore the stability of the trenches must be ensured. The structures like soil trench, when dug in weak soils, the trench sides may collapse or cave-in or fall in, under the action of the stresses. The main forces are:

1. Active Earth Pressure

2. If soil is saturated, then pore water pressure must be considered as well. In some cases dewatering may be needed to be done from the bottom of the trench.

Q.2

Cofferdam is built within a water body, such as river or reservoir or oceans (preferably at shallow depths) to provide the dry space to work for building a structure. When built completely under water it is totally enclosed and then water is pumped out, and the air is pumped in from external source.

Coffer dams are commonly made of steel sheet pile, rock, gabions, concrete jersey barriers, vinyl tubes filled with water, or wood.