Geotechnical Engineering

Consolidation

The slow settlement of a saturated clay as water is squeezed out of its pores under a new load.

When a load is added over a saturated clay, the pore water carries it at first. As the water drains, the load transfers to the soil skeleton, the void ratio falls and the layer settles. For a normally consolidated clay the final settlement is C_c·H/(1 + e₀)·log(σ′_f/σ′₀).

How long it takes depends on the drainage path, not the layer thickness: t = T_v·H_dr²/c_v. A layer drained top and bottom has a drainage path of half its thickness, so it consolidates four times faster than the same layer drained on one side only.

How much of the FE Civil exam is Geotechnical Engineering?