Dock Builders

See Crew, Pile.

Dog-Leg Pile

A pile curved or bent in driving.

Dolly

See Cushion Blocks.

Dolphin

1. A cluster of piles driven and bound together at the top to protect bridge piers and docks from heavy marine traffic.
2. A marine structure founded on piles used to moor, anchor, breast or turn a vessel.
3. A large diameter pile or casing to accomplish preceding uses. Also called mooring dolphin or breasting dolphin.

Doodle or Dummy Hole

An empty closed-end tubular section, driven into the ground within operating radius of a pile rig. Corrugatedshell is lowered into the hole to facilitate inserting a mandrel, thereby allowing the use of shorter leads or longer lengths of shell. The shell and mandrel are raised together out of the doodle hole and moved to required pile location. Also called Rat Hole and Make-Up Pile.

Double Acting Hammer

A pile hammer in which fluid lifts the ram on the up stroke and additional fluid, redirected by valving, acts in concert with gravity on the down stroke.

Double Jack

A heavy double-headed, long handled hammer.

Double Sheets

Two sheet piles, interlocked and tack welded then handled together for installation and pulling.

Double-Acting Diesel Hammer

See Diesel Hammer, Closed-End.

Dowel

Wood or steel pin used to connect two structural members. A short piece of steel bar imbedded in the pour to tie adjoining pours together.

Downdrag

See Negative Skin Friction.

Drawdown

The lowering of the level of the groundwater table that occurs as a work area is dewatered for construction. Also lowering water behind a dam.

Dredging

Excavatiging underwater, usually with floating equipment; it may be an elevator ladder, hydraulic suction, grapple, grab or dipper bucket, scraper, dragline, clam shell or backhoe.

Drift

A deposit of loose detrital materials, fragments of rocks, boulders, sand, gravle, clay or other soils driven together by ice, wind or water. See Glacial Till.

Drift Bolt

1. A metal rod driven unto a hole bored in timber, the hole having a smaller diameter than the rod; usual purpose is to hold two or more timbers together.
2. In steel erection a tapered "drift pin" is used to align holes at connections.

Drilled Pier

A larger diameter, up to 10 ft or more, opening excavated to bearing strata and filled with concrete -- cased or uncased.

Drilled Pile

See Augered Pile, Drilled Pier.

Drilled Shaft

See Augered Pile.

Drilled-In-Caisson

An open-end pipe driven to rock, cleaned out and a socket drilled into rock to receive a steel core (H, WF, or bars) then socket and pipe are filled with concrete. Core, concrete and pipe contribute to high carrying capacity.

Driller's Stroke

Height of fall of a drop hammer weight (140 lb or more) to drive a casing or soil sampling tool. The weight is usually raised by wrapping a rope around a powered continuously rotating spool or "cat-head." The weight is raised by holding the rope taut thus raising the hammer, then allowing slack in the rope to let the hammer fall to hit either the casing or the sampler rods. This distance from the top of the casing to the height before release is called the fall or driller's stroke. See N Value.

Drilling Bucket

A closed rotary boring tool with its cutting edge at its base. Spoil is removed from the bucket by swinging it to one side of the bore and releasing the hinged bottom of the bucket.

Drive Band

Steel band secured around the top of a timber pile to prevent damage while being driven.

Drive Cap

Steel accessory placed over a pile to prevent damage from driving. It is suspended beneath a hammer by cables; it contains a well or recess on top for cushion material and for seating the anvil, if used. The bottom is formed to accept a specific shape pile, along with its cushion if used. The outside incorporates lug or insert slot for attaching to the lead system. Also called Anvil Block, Bonnet, Cap, Driving Head, Helmet, Follow Cap, Rider Cap, Shield.

Drive Shoe

See Pile Point.

Drive Sleeve

A type of pile splice used at the joints of pipe pile to splice two sections together.

Drive-Fit Collar

A steel collar used for splicing pipe piles. The "drive-fit" simply means that both pieces of pipe fit inside the collar and after the first blow of the hammer, the fit is tight due to the taper of the inside of the collar. Does not normally require welding; pipe is held by friction.

Driving Criteria

1. Requirement for resistance of a pile to penetration, stated in blows per infrement of depth.
2. Required tip elevation of pile. See Refusal.

Driving Formula

See dynamic formula.

Driving Head

See Drive Cap.

Driving Head Attachments

Each pile type requires possibly a different shaped head attachment for the hammer. The purpose is to hold the pile firmly in place during the upstroke of the ram, and to prevent distortion to the top of the pile.

Driving Log

Field Record of each driven pile including location number, hammer model, pile type, blow count per unit of penetration, final resistance, driven length, etc. Also called Log or Pile Log.

Driving Plan

The driving plan is a written plan that describes the step by step procedure of the entire pile driving operation from pile manufacturing, arrival, storage, hoisting, driving, releasing from safety line and post driving with an emphasis on safety. Everything involved in the operation of installing the pile should be described in the driving plan and provided to all personnel within the Driving Theater.

Driving Point

See Pile Point.

Driving Shoe

See Pile Point.

Driving Theater

The entire area where, in the event of a pile accident resulting in the collapse of the crane and leader system personnel on the ground could be struck with falling equipment or objects dynamically effected by falling equipment such as stored piles, towers, other standing equipment. Please see Driving Plan.

Drop Hammer

See Gravity Hammer.

Dry Sampling

A method of sampling soil by augering a hole in the ground with a sampler or sample spoon attached to the end of the auger. The object is to obtain a complete undisturbed sample of the natural soil for analysis. Also called Core Boring.

Dry Shack

A place for changing in and out of work clothes and eating lunch.

Dump Scow

A barge with a pocket or hole within its structure to hold large loads of rock, dirt, or other materials.

Dunnage

Temporary timber decking. Timbers, wood strips or crating used between rows or layers of construction materials to provide air and lifting space.

Duplex Nail

A double headed nail used in forming and designed for easy removal.

Dutch Block

Y-type rigging system, to operate diesel hammer with a single line, which supports both the lead and hammer.

Dutch Cone

See Penetrometer.

Dutch Leaders

Pile hammer leads composed of two holes or pipes which are loosely coupled at the boom point and the base and the hammer is guided between the pipes.

Dynamic force

1. Energy Delivered by a pile hammer to change the state of rest of a pile. The force of the hammer is equal to the mass of the ram of the hammer times its acceleration.
2. Force applied to a pile by a rotating eccentric weight vibratory pile driver/extractor. Mathematical formula: