Subsoil drainage (The water table/groundwater/stability)

Question 1

What is surface water?

Answer 1

Rainwater that falls on the surface of the ground

Question 2

What is ground water?

Answer 2

Water that is held in soils at and below the water table

Question 3

What are subsoil drains be used to improve? (see Titas Library or page 29 of pdf for examples)

Reasons for using them?

Answer 3

The run of Surface water water and the drainage of ground water to maintain the water table at some depth below the surface for the following reasons:

To improve the stability of the ground (sloping sites/poor bearing strata!)
To avoid surface flooding
To alleviate or avoid dampness in basements
To reduce humidity in the immediate vicinity of buildings

Question 4

Groundwater/Land drains are used generally on what type of land?

Answer 4

One way sloping land

Question 5

Groundwater/Land drains are used generally laid in trenches at what depth?
What is the normal hole diameter of the pipes?

Answer 5

0.6m and 0.9m in heavy soils, and 0.9 to 1.2m in light soils.
Hole diameter - 75mm and 100mm for main drains, 65 or 75mm for branches