Straightening and Aligning Piles

Piles should be straightened when any misalignment is noticed during pile driving. The accuracy of alignment that should be sought for the finished job depends on various factors, but if a pile is more than a few inches out of its plumb line, an effort should be made to true it up. The greater the penetration along the wrong alignment, the harder it is to get the pile back to plumb.

One method of alignment is to use pull from a block and tackle (fig. 12-70) with the impact of the hammer jarring the pile back into line. The straightening of steel bearing piles must include twisting of the individual piles to bring the webs of the piles parallel to the center line of the bent.

Figure 12-70.-Realigning pile using block and tackle.

Another method of alignment is to use a jet (fig. 12-71), either alone or jointly, with the block-and-tackle method

When all piles in a bent have been driven, they may be pulled into proper spacing and alignment with block and tackle and an aligning frame, as shown in figures 12-72 and 12-73.

Pulling Files

A pile that has met an obstruction, that has been driven in the wrong place, that has split or broken in

Figure 12-71.-Realigning pile by jetting.

Figure 12-72.-Aligning frame used for timber pile bent.

Figure 12-73.-Aligning and capping steel pile bents.

driving, or that is to be salvaged (steel sheet piles are frequently salvaged for reuse) is usually extracted (pulled). Pulling should be done as soon as possible after driving; the longer the pile stays in the soil, the more compact the soil becomes, and the greater the resistance to pulling will be. Methods of pulling piles are as follows:

1. In a direct lift method, a crane palls the pile. The crane hoist line is rigged to the pile through the use of wire rope rigging, and an increase in pull is gradually applied to the pile. Lateral blows from a skull cracker (heavy steel ball swung on a crane line to demolish walls) or a few light blows on the butt or head with the pile-driving hammer are given to break the skin friction, and the crane pull is then increased. If the pile still refuses to extract, it may be loosened by jetting, air extractors, or beam pullers.

2. The 5,000-pound pneumatic, or steam, hammer may be used in an inverted position to pull piles. The hammer is turned over and the wire rope rigging is attached to it and the pile is extracted. A pneumatic extractor may also be used. The crane line, holding the hammer or extractor, is hoisted taut; and the upward blows of the hammer ram on the sling, plus the pull of the crane hoist, are usually enough to pull the pile.

3. Tidal lift is often used to pull piles driven in tidewater. Rigging, wrapped around the piles, is attached to barges or pontoons at low tide; the rising tide pulls the piles as it lifts the barges or pontoons.