What is "pile bridge"

Pile \Pile\, n. [AS. p[=i]l arrow, stake, L. pilum javelin; but cf. also L. pila pillar.]

1. A large stake, or piece of timber, pointed and driven into the earth, as at the bottom of a river, or in a harbor where the ground is soft, for the support of a building, a pier, or other superstructure, or to form a cofferdam, etc.

   Note: Tubular iron piles are now much used.

2. [Cf. F. pile.] (Her.) One of the ordinaries or subordinaries having the form of a wedge, usually placed palewise, with the broadest end uppermost.

   Pile bridge, a bridge of which the roadway is supported on piles.

   Pile cap, a beam resting upon and connecting the heads of piles.

   Pile driver, or Pile engine, an apparatus for driving down piles, consisting usually of a high frame, with suitable appliances for raising to a height (by animal or steam power, the explosion of gunpowder, etc.) a heavy mass of iron, which falls upon the pile.

   Pile dwelling. See Lake dwelling, under Lake.

   Pile plank (Hydraul. Eng.), a thick plank used as a pile in sheet piling. See Sheet piling, under Piling.

   Pneumatic pile. See under Pneumatic.

   Screw pile, one with a screw at the lower end, and sunk by rotation aided by pressure.

A pile bridge is a structure that uses foundations consisting of long poles (referred to as piles), which are made of wood, concrete or steel and which are hammered into the soft soils beneath the bridge until the end of the pile reaches a hard layer of compacted soil or rock. Piles in such cases are hammered to a depth where the grip or friction of the pile and the soil surrounding it will support the load of the bridge deck. Bridging solely using the pile method is nowadays a rare occurrence.