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Glossary of Piledriving and Foundation Construction Terms

Welcome to the APE Gloassary for piledriving and foundation construction terms. This is a great place to look for terms that you may be unfamiliar with when working with or researching piledriving technologies. This glossary also contains terms unrelated to piledriving, but that are frequently used on and around foundation construction projects. If you have a question or have term that you would like to add and do not know who to call please contact the APE Headquarters in Washington at (800) 248-8498. Business hours are from 8:00 AM to 5:00 PM Pacific Time. For less immediate inquiries, or if you would like an APE sales representitive to get in contact with you, please visit the APE Contact Request Form.

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Letter D

Dam A structure constructed to obstruct the flow or to impound water.
Dancing The term "dancing" or "bouncing" is used to describe a vibratory pile driver/extractor's behavior when driving a pile that has hit a rock layer or some other obstruction causing the vibro to jump up and down in an erratic pattern of amplitude. The vibro suppressor housing "dances" due to its lack of capacity to absorb the unwanted erratic amplitude, thus transferring unwanted vibration into the housing and crane line. This, of course, will overheat and damage or destroy the rubber elastomers in the suppressor housing or destroy the bearings in the gearbox or both. Do not operate a vibratory pile driver/extractor in this manner. Should the contractor wish to allow the vibratory pile driver to “dance” then the machine should be shut down at once and an agreement should be made where the contractor agrees to accept all responsibility for damages. Those damages could be to the vibratory suppressor, gearbox, clamp attachment, bolts and fasteners as well to the crane line and boom. In some cases, such as when the pile lands on a buried wood pile or a layer of hard soil, the vibratory pile driver/extractor may experience “dancing” for a second or two before breaking through the obstacle. It is up to the judgment of the pile crew to determine if the “dancing” is minor or harmful. In any case, “dancing” will cause excessive wear on all components involved including the crane line and boom. Driving piles is an art and a skill. Rookie pile drivers should shut the machine down the moment the hammer is dancing. A skilled pile driver may attempt to slow the machine down by lowering the engine rpm (which slows down the machine because the slower rpms of the engine will reduce hydraulic flow). Slowing the machine down may reduce or eliminate the “dancing” problem. Lifting up on the suppressor housing may also prevent “dancing”. Hard layers may require pre-drilling or the use of an impact hammer or a combination of both. In permafrost soil conditions a combination of predrilled holes and hot water or even steam jetting has been used. Consult the factory and asked to speak with an experienced person regarding what to do in case of “dancing”.
Dap Incision or notch cut in timber into which the head of a pile or other timber is fitted.
Dead Load Weight of the structure only.
Deadman A pile, cluster of piles or buried timber or a wall driven to withstand a horizontal force as through a tie rod fastened to a retaining wall. See Anchor Pile.
Death Zone Area Area around the pile as it is being driven. This Death Zone Area includes all area around the pile driving rig that is subject to danger should the crane and leads tip over. Only the trained pile drivng crew should be allowed to work in this area during pile driving operations. Never stand next to the pile while it is in the act of being driven. Never check plumbness by placing level on a pile that is in the act of being driven. Do not stand anywhere under the pile as it is being driven due to the possibility of the pile breaking or parts or pieces falling from the pile hammer or leads or any other support structure. Please note that mis-placed tools, shackles, and any other items placed on the leads or hammer have been known to fall and cause injury. Please stand clear and up wind.
Decrementation Removal of a load in steps at completion of test loading. See incremental loading.
Density The weight or mass per unit of vilume. In reference to soil, the term usually indicates weight per unit volume and is synonymous with unit weight.
Depth of Fixity Distance from the ground surface to the depth at which a pile is held firmly by the soil.
Desanding Plant Equipment used to filter or desand contaminated bentonite slurry prior to its reuse.
Design Engineering Firm The professional organization responsible for the design, plans and specifications to fulfill the cope of work to be performed to sucessfully complete the design of a project. The firm may also monitor and observe the construction of the project. See A/E.
Design Load The load which the pile is intended to carry without excessive movement and with an acceptable factor of safety against plunging failure.
Deviation Variation from the designated plan location or elevation.
Dewatering 1. The procedure utilized to remove water from a construction area such as pumping from an excavation or location where water covers the planned surface.
2. The procedure used to lower the groundwater table in order to obtain a "dry" area in the vicinity of an excavation which would otherwise fill with water.
DFI Deep Foundations Institute.
Diaper Term used for a woven burlap type fabric tacked over a cut wood piling to hold the bear shit in place for protection against deterioration. Also a term for an absorbant material or pad used to contain and clean up spilled liquids such as oil, hydraulic fluid, gas, etc.
Diaphragm wall See Slurry Trench Wall.
Diaphragm-Type Cellular Cofferdam A structure made of steel sheet piles with each of the inner and outer walls consisting of a series of arc segments, which are connected at their intersections with diaphragms that exctend through the cofferdam to form a series of cells. The cells are filled with earth, sand, gravel or rock. See circular-type cofferdam.
Diesel Hammer A pile hammer, which carries its own diesel fuel to generate power internally.
Diesel Hammer, Closed-End A diesel pile hammer in which the upward flight of the ram is arrested by compressing air, above the ram to form an "air spring." Also called Double-Acting Diesel Hammer.
Diesel Hammer, Open-End A diesel pile hammer in which the upward flight of the ram is arrested by gravity. Also called Single-Acting Diesel Hammer.
Diesel I Program TItle of a proprietary computer program for solving wave equations for diesel hammers.
Dieseling Undesirable precombustion of the fuel in a diesel pile hammer (usually due to overheating or improper fuel). Also called Prefiring, Preignition.
Differential-Acting Hammer A fluid-powered hammer in which fluid lifts the ram un the op stroke and is exhausted into and combined with addition fluid entering over the piston to take advantage of differential piston areas to accelerate the ram and to act in concert with gravity on the down stroke.
Dike An impervious barrier to control movement of water.
Dip Angle of inclination a fault stratum makes with the horizontal plane. See Strike.
Direct Circulation See Reverse Circulation.
Displacement Pile A solid pile, or hollow pile, driven with the lower end closed, which displaces an equivalent soil volume by compaction or by lateral or vertical displacement of the soil, such as timber, closed-end pipe or precast concrete piles. A Franki pile.
Disturbed Sample A sample of soil taken without effectively minimizing disturbance of the soil mass.
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:

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