Question

Consider the following statements:
1. The hydraulic head at a point in the soil
includes piezometric head as well as datum head.
2. Piping in soil occurs when effective pressure becomes equal to zero.
3. Piping in soil occurs when soil is highly porous.
Which of these statements is/are correct?

• A. 1. 2 and 3
• B. 1 and 2 only
• C. 2 and 3 only
• D. 2 only

Answer 1

The correct option is D 2 only

(d)
• Piezometric head = Pressure Head + Datum Head. Piezometric head already includes datum head.
• When effective pressure becomes zero this leads to erosion of the soil, this begins near the downstream toe but may lengthen progressively towards, the upstream. This phenomenon is known as piping, because erosion occurs in the form of a pipe or closed channel underneath the structure.
• Highly porous refers to gravel in which large discharge is required for piping. But piping can also occur in sands which are comparatively lesser porous and require lesser discharge.