Apply normal safety precautions to hand power tools used to prepare piles for driving and in cutting off, straightening, and aligning piles after they are driven.

Wearing safety shoes is required. Be sure you and all your crew are wearing hard hats. Mill scale may fly from a steel pile while it is being driven.

During the first few feet of driving a pile, keep personnel out of the way as much as possible so that if the tip of the pile were to strike an obstacle and slide out of line, no one would be struck by the pile.

During actual pile driving, protect your ears. When working over water, wear life jacket and make sure crew members do likewise. Use safety belts as required.

Characteristics of Different Piles

As a Builder, you will be most concerned with timber piles. Steel piling ranks next in importance, especially where the construction must accommodate heavy loads or the foundation is expected to be used over a long period of time. Steel is best suited for use as bearing piles where piles must be driven under the following conditions:

Piles are longer than 80 feet.

Column strength exceeds the compressive strength of timber.

To reach bedrock for maximum bearing surface through overlying layers of partially decomposed rock.

To penetrate layers of coarse gravel or soft rock, such as coral.

To attain greater depth of penetration for stability.

Concrete and composite piles are seldom used because they require material and equipment that is not normally available through military supply channels. They are likely to be used in cases where local materials are readily available, whereas standard military piling would have to be received in large quantities from CONUS. Interlocking steel sheetpiling is often used in military construction, but concrete-steel piling can be manufactured in the field when local material is available.

Precautions during Pile Driving

Be careful during driving to avoid damage to the pile, the hammer, or both. If the pile driver shifts position during driving, the blows of the hammer will be out of line with the axis of the pile and both the pile and the hammer may be damaged.

Watch the piles carefully for any sign of a split or break below ground. When you are driving pile and it suddenly becomes easier to drive or the pile suddenly changes direction, a break or split has probably occurred. When this happens, pull the pile as soon as possible, because further driving is useless.

"SPRINGING" means that the pile vibrates too much laterally. Springing may occur when a pile is crooked, when the butt has not been squared off properly, or when the pile is not in line with the fall of the hammer. In all pile driving, make sure the fall of the hammer is in line with the pile axis; otherwise, the head of the pile and the hammer may be damaged severely and much of the energy of the hammer blow lost.

Excessive BOUNCING may come from a hammer that is too light. However, it usually occurs when the butt of the pile has been crushed or broomed, when the pile has met an obstruction, or when it has penetrated to a solid footing. When a double-acting hammer is being used, bouncing may result from too much steam or air pressure. With a closed-end diesel hammer, if the hammer lifts on the upstroke of the ram piston, the throttle setting is probably too high. Back off on the throttle and control just enough to avoid this lifting. If the butt of the timber pile has been crushed or broomed more than an inch or so, cut it back to sound wood before you drive it any more.

When a pile has reached a level where 6 blows of a drop hammer, 20 blows of a steam or air hammer, or 10 blows of a-diesel hammer per inch will not drive it more than an average of one-eight inch per blow, the pile has either hit an obstruction or has been driven to REFUSAL. In either case, further driving is likely to break or split the pile. If the lack of penetration seems to be caused by an obstruction, try 10 or 15 blows of less than maximum force; they may cause the pile to displace or penetrate the obstruction. For obstructions which cannot be disposed of in this manner, it is often necessary to PULL (extract) the pile (see next section) and blast out the obstruction with an explosive lowered to the bottom of the hole.