Quicksand is a condition and not a soil type. This condition is created in saturated thick layers of loose fine sandy soils when disturbed either due to vibration, such as, from pile driving in the neighborhood, or due to pressure of flowing water (at the time of heavy pumping in excavation).
The particles, in trying to achieve a closer packing will force the pore water upwards and out at the surface, and if this has sufficient velocity to cause a flotation or boiling up of the particles, the sand particles begin to move horizontally and get lifted up, the bottom sand rising up and its space is occupied by the adjoining particles, thus making a regular movement. The finer the sand the more readily it is affected by a flow of water, especially if it contains a little clay.
Piping is a particular form of quicksand. This type of condition is met with in coffer dam failure. Under such conditions the material may be carried off from under a structure which can result in the settlement of buildings at a considerable distance. Even if a full flow is not created, the stability of the soil is lessened due to the upward seepage pressure. The condition can be corrected by lowering head of water by underground drainage.