The process of removing excess water from the underground soil mass is called drainage.
Facilities of Providing Drainage
For the construction and operation of foundation work, drainage facilitates the following:
1) It intercepts the seepage flow.
2)It lowers down the groundwater table.
3)It gives dry working condition.
4)It increases the effective stress and thereby helps to improve the shear strength of soil mass.
5)It increases the stability of excavated slopes.
6)It quickens the process of consolidation.
7) It reduces the lateral stresses on sheeting and bracing.
Methods of Providing Drainage
The following methods are adopted for drainage of excess water from the underground soil mass:
a) Slump and ditches.
b) Sheeting and open pumping.
c) Wellpoint system.
d) Deep well system.
e) Vacuum dewatering system.
f) Electro-osmosis system.
g) By providing a sand drain.
h) By the sumps in the well.
i) By side drain.