Types of Piles

Equipment Operator Basic - Beginning construction equipment operators manual
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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. Types of Piles The principal use of piles is for the support of bridges, buildings, wharves, docks and other structures, and in temporary construction. A pile transfers the load into an underlying bearing stratum by either of the following: 1. Friction along the embedded length of the pile 2. Point bearing plus any bearing from the taper of the pile A pile maybe classified roughly as friction or end bearing, according to the manner in which they develop support. The load must be carried ultimately by the soil layers around and below the points of the piles, and accurate knowledge of the compressibility of these soil layers is of utmost importance. Some of the common terms used with piles are as follows: 1. Piles. A pile is a load-bearing member made of timber, steel, concrete, or a combination of these materials, usually forced into the ground to transfer the load to underlying soil or rock layers when the surface soils at a proposed site are too weak or compressible to provide enough support. 2. Pile foundation. A pile foundation is a group of piles that supports a superstructure or a number of piles distributed over a large area to support a mat foundation. 3. Bearing piles. Piles that are driven vertically and used for the direct support of vertical loads are called bearing piles. Bearing piles transfer the load through a soft soil to an underlying firm stratum. They also distribute the load through relatively soft soils that are not capable of supporting concentrated loads. 4. End-bearing piles. Typical end-bearing piles are driven through very soft soil, such as a loose silt-bearing stratum underlain by compressible strata. Remember this factor when determining the load the piles can support safely. 5. Friction piles. When a pile is driven into soil of fairly uniform consistency and the tip is not seated in a hard layer, the load-carrying capacity of the pile is developed by skin friction. The load is transferred to the adjoining soil by friction between the pile and the surrounding soil. The load is transferred downward and laterally to the soil. 6. Combination end-bearing and friction piles. Many piles carry loads by a combination of friction and end bearing. For example, a pile may pass through a 12-51

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