Figure 8-27. - Wire-rope sling used with 5,000-pound airstream hammer to pull piles.

blows from a HEADACHE BALL (heavy steel ball, swung on a crane whip to demolish walls) or a few light blows on the butt or head with a driving hammer are given to break the skin friction. The crane pull is then increased to maximum capacity. If the pile still will not start, it maybe loosened by jetting or the lift of the crane may be supplemented by the use of hydraulic jacks.

The 5,000-pound double-acting hammer may be used in an inverted position to pull piles. The hammer is turned over, and a wire-rope sling is passed over it and attached to the pile (fig. 8-27). The hammer whip is heaved taut, and the upward blows of the hammer ram on the sling plus the pull of the hammer whip are usually enough to pull the pile.

TIDAL LIFT is used often to pull piles driven in tidewater. Slings on the piles are attached to barges or pontoons at low tide; the rising tide pulls the piles as it lifts the barges or pontoons. To avoid the danger of tipping barges over, place a barge on each side of the pile with the lifting force transmitted by girders extending across the full width of both barges.

PLANNING AND ESTIMATING PILE-DRIVING OPERATIONS

So far, you have a thorough understanding of the materials used, and the principles of, and the capabilities of driving pile. Preparing estimates, such as man-days, and equipment, are usually left up to the Equipment Operators (EOs), but should not present any real problem for you.

Manpower estimates (fig. 8-28) for bearing piles are based on a typical crew consisting of the following members:

One crew leader.

One crane operator.

Figure 8-28. - Table from P-405.