Bligh’s creep theory | Creep length | Percolation co-efficient

Bligh’s creep theory:

According to Bligh’s theory, water creeps along the bottom contour of the structure. The length of the path of water is called the length of creep and the loss of head is proportional to the length. If HL is the total head loss between upstream and downstream and L is the length, then the loss of head per unit of creep length (i.e. H L /L) is called the hydraulic gradient. Bligh’s theory makes no discrimination between horizontal and vertical creeps.

Percolation co-efficient:

Due to creep effect loss of head takes place. The loss of head per unit length is known as percolation co-efficient. It is also known as hydraulic co-efficient.

Bligh’s creep co-efficient:

If we take inverse of percolation co-efficient, it is known as Bligh’s co-efficient.

Limitations of Bligh’s theory:

• The parallel and perpendicular creeps are same. There is no distinction between them.

• There is no importance of escaping gradient.

• There is no head loss.

• Pressure is not linear.

• It is followed by sine curve.

Drawback:

Creep effect is a big problem in all civil engineering projects. There should be complete study of this process because it greatly affects efficiency of projects. Civil engineer must have proper treatment of this problem because it’s harmful. Bligh’s made an effort and put forward this theory of creep effects.