Methods to accelerate consolidation

Consolidation time $t = T_v H_{dr}^2/c_v$. It can be reduced by shortening the drainage path, increasing $c_v$, or speeding the dissipation of pore pressure. Methods:

1. Vertical sand drains: closely spaced vertical columns of sand (diameter 20 to 60 cm) through the clay shorten the drainage path from the clay thickness to half the drain spacing (radial drainage). Water flows horizontally to the drains, which is faster than vertical flow in thick clay.
2. Prefabricated vertical drains (wick drains): plastic band drains, same function, installed quickly and cheaply.
3. Surcharge (preloading): a temporary load larger than the future structural load is placed to cause most of the settlement before construction; it is removed later.
4. Vacuum preloading: a vacuum applied under a membrane increases the effective stress without extra fill.
5. Sand blanket / drainage layer: a layer of free draining sand at the top (and bottom) provides double drainage.
6. Electro-osmosis and lowering the water table (dewatering), or consolidation by heating, are less common.