Question

The hydraulic gradient i is given by _________

(a) \(i=\frac{γ_w ∂h}{∂z}\)

(b) \(i=\frac{∂h}{γ_w ∂z}\)

(c) \(i=\frac{\overline{u}∂h}{∂z}\)

(d) \(i=\frac{∂h}{∂z}\)

I have been asked this question in semester exam.

This is a very interesting question from Terzaghi’s Theory of One Dimensional Consolidation in division One Dimensional Consolidation of Geotechnical Engineering I

Answer 1

Right answer is (d) \(i=\frac{∂h}{∂z}\)

The explanation is: The hydraulic gradient is the driving force that causes groundwater to move in the direction of maximum decreasing total head. The hydraulic gradient is the change in total head divided the distance over which the change occurs.

∴ \(i=\frac{∂h}{∂z}.\)