FM 5-134

C H A P T E R 4

PILE INSTALLATION

Section I. PREPARATION OF PILES FOR DRIVING

4-1. Preparation of timber piles.

Timber piles selected for a structure should belong enough so that the butts are 2 or 3 feethigher than the finished elevation after thepiles are driven to the desired penetration.(Methods of predetermining pile lengths aredescribed in chapter 5.) Timber piles requirelittle preparation or special handling;however, they are susceptible to damageduring driving, particularly under harddriving conditions. To protect the pile againstdamage, the following precautions should betaken.

a. Fresh heading. When hard driving isexpected, the pile should be fresh headed byremoving 2 to 6 inches of the butt. Removinga short end section allows the hammer totransmit energy more readily to the lowersections of the piles. Butts of piles that havebeen fresh headed should be field treatedwith creosote and coal tar pitch (chapter 8),after the pile has been driven to the desiredpenetration.

OPERATIONS

b. Fitting. Proper fit between the butt of thepile and the driving cap of the hammer is themost important factor in protecting the pilefrom damage during hard driving. The buttof the pile must be square cut, shaped to fitthe contour of the driving cap, and a littlelarger than the dimensions of the cap so thewood will be compressed into the driving cap.Under most driving conditions the tip of atimber pile should be left square withoutpointing. The following points should be keptin mind when fitting timber piles.

Pointing timber piles does little to in-crease the rate of penetration.

Piles with square tips are more easilykept in line during driving and providebetter end bearing.

For very hard driving, steel shoes protectthe tips of piles (figure 4-1, 1). Steel platesnailed to blunt tips (figure 4-1, 2) offerexcellent protection.

c. Wrapping. If a driving cap is not used, orif crushing or splitting of the pile occurs, thetop end of the pile should be wrapped tightlywith 12-gage steel wire to forma 4-inch band.The steel wire should be stapled firmly in

4-1

FM 5-134

place. This is a simple method of protectingpile butte during hard driving. Steel strappingabout 1¼ inches wide will also provideadequate protection. Strapping should en-circle the pile twice, be tensioned as tightly aspossible, and be located approximately twofeet from the butt.

d. Splicing. Piles can be spliced if singlesections of the required length are notavailable or if long sections cannot behandled by available pile drivers. Generally,

decreasing pile spacing or increasing thenumber of piles is preferable to splicing.Except in very soft soils or in water, thediameter of the complete splice should not begreater than the diameter of the pile (figure4-2). The ends of the piles must be squared,and the diameter trimmed to fit snugly in the8-inch or 10-inch steel pipe. Steel splice platesare also used (figure 4-2).

e. Lagging. Lagging a friction pile with steelor timber plates, planks, or rope wrapping

4-2

FM 5-134

can be used to increase the pile’s load-carryingcapabilities.

4-2. Preparation of steel piles.

a. Reinforcing. Point reinforcement isseldom needed for H-piles; however, if drivingis hard and the overburden contains ob-structions, boulders, or coarse gravels, theflanges are likely to be damaged and the piles

may twist or bend. In such cases H-piles(figure 4-3) and pipe piles (figure 4-4) shouldbe reinforced.

b. Cleaning. Pipe piles driven open-ended,must be cleaned out before they are filledwith concrete. Ordinarily they are closedat the lower end, usually with a flat plate(figure 4-4). In a few soils, such as stiff plasticclays, the overhang of the plate should be

4-3

FM 5-134

4-4

FM 5-134

eliminated. Such pipe piles can be inspectedafter driving. Damaged piles should be iden-tified and rejected if not repairable.

c. Splicing. H-piles can be spliced anddesigned to develop the full strength of thepile both in bearing and bending. This isdone most economically with butt-weldedsplices (figure 4-5). This method requires thatthe pile be turned over several times during

the welding operation. Various types of plateand sleeve splices can be used (figure 4-6).Splicing is often performed before the pilesare placed in the leads so pile-drivingoperations are not delayed.

d. Lagging. Lagging is of questionable valueand if attached near the bottom of the pile,will actually reduce the capacity of the pile.

4-5

FM 5-134

4-6

FM 5-134

4-7

FM 5-134

4-3. Preparation of concrete piles.

Precast concrete piles should be straight andnot cambered by uneven prestress or poorconcrete placement during casting.

a. Reinforcing. Reinforcing of precastconcrete piles is done in the manufacturing.The top of the pile must be square orperpendicular to the longitudinal axis of thepile. The ends of prestressing or reinforcingsteel should be cut flush with the end of thepile head to prevent direct loading by the ramstroke. Poured concrete piles may be re-inforced with steel reinforcing rods.

b. Splicing or cutting. Precast concretepiles are seldom, if ever, spliced. If the drivinglength has been underestimated, the pile canbe extended only with considerable difficulty.The piles are expensive to cut if the lengthhas been over estimated. Poured concretepiles should not require splicing as length ispredetermined in the planning stages.

Section II. CONSTRUCTIONPROCEDURES

4-4. Positioning piles.

When piles are driven on land, for example abuilding foundation, the position of each pilemust be carefully established, using availablesurveying equipment. A simple template canbe constructed to insure proper positioning ofthe piles. Piles generally should not be drivenmore than three inches from their designlocation. Greater tolerances are allowed forpiles driven in water and for batter piles.

4-6. General driving procedures.

Piles are set and driven in four basic steps(figure 4-7).

a. Positioning. The pile driver is broughtinto position with the hammer and cap at thetop of the leads (figure 4-7, 1).

4-8

b. Lashing. Generally, the pile line is lashedabout one third of the distance from the top ofthe pile, the pile is swung into the helmet, andthe tip is positioned into the leads (figure 4-7,2). A member of the handling crew can climbthe leads and, using a tugline, help align thepile in the leads.

c. Centering. The pile is centered under thepile cap, and the pile cap and hammer arelowered to the top of the pile. If a drophammer is used, the cap is unhooked from thehammer (figure 4-7, 3).

d. Driving. The hammer is raised anddropped to drive the pile (figure4-7, 4). Drivingshould be started slowly, raising the hammeronly a few inches until the pile is firmly set.The height of fall is increased gradually to amaximum of 6 feet. Blows should be appliedas rapidly as possible to keep the pile moving.Repeated long drops should be avoided sincethey tend to damage the top of the pile.

4-6. Driving requirements.

Careful watch must be kept during driving toavoid damage to the pile, pile hammer, orboth. Precautions and danger signs includethe following

a. Support. The pile driver must be securelysupported, guyed, or otherwise fastened toprevent movement during driving.

b. Refusal. Refusal is reached when theenergy of the hammer blow no longer causespenetration. At this point, the pile has reachedrock or its required embedment in the bearingstratum. It is not always necessary to drivepiles to refusal. Friction piles frequently mustbe driven only far enough to develop thedesired load bearing capacity. In certaintypes of soils, such as a very soft organic soilor deep marsh deposit, a considerable lengthof pile may be necessary to develop adequateload capacity. Driving in such soils isfrequently easy as piles may penetrate several

FM 5-134

4-9

FM 5-134

feet under a single hammer blow. It isimportant that driving be a continuousprocedure. An interruption of even severalminutes can cause a condition of temporaryrefusal in some types of soils, thus requiringmany blows to get the pile moving again.

c. Timber piles. Timber piles are frequentlyoverdriven when they are driven to endbearing on rock (figure 4-3). If the pile hits afirm stratum, depth may be checked bydriving other piles nearby. If the piles stop atthe same elevation, indications are that afirm stratum has been reached. Followingare items to be watched for when drivingtimber piles.

(1) Breaking or splitting below ground. Ifthe driving suddenly becomes easier, or ifthe pile suddenly changes direction, thepile has probably broken or split. Furtherdriving is useless as bearing capacity isunreliable. Anew pile must be driven closeto the broken one, or the broken one pulledand a new one driven in its place.

(2) Pile spring or hammer bounce. The pilemay spring or the hammer may bouncewhen the hammer is too light. This usuallyoccurs when the butt of the pile has beencrushed or broomed, when the pile has metan obstruction, or when it has penetratedto a solid footing.

(3) Double-acting hammer bounce. When adouble-acting hammer is being used, toomuch steam or air pressure may causebouncing. When using a closed-ended dieselhammer, lifting of the hammer on theupstroke of the ram piston can causebouncing. This is caused by too high athrottle setting or too small a hammer.Throttle controls should be backed off justenough to avoid this lifting action.

(4) Crushed or broomed butt. If the butt of atimber pile has been crushed or broomed

4-10

for approximately 1 inch, it should be cutback to sound wood before driving iscontinued. There should be no more thanthree or four final blows per inch for timberpiles driven with a diesel, steam, or airhammer. Further driving may fracture thepile or cause brooming.

d. Steel piles. In driving steel piles, par-ticular care must be taken to see that thehammer strikes the top of the pile squarely,with the center of the hammer directly overthe center of the pile. Watch for the following.

(1) Slack lines. A hammer suspended froma slack line may buckle the top section andrequire the pile be trimmed with a torchbefore driving can proceed. Driving caps(previously described) will prevent thistype of damage to H-piles.

(2) Alignment. When a steel pile is drivenwith a flying hammer (free-swing hammer),the pile should be aligned with guys (figure4-9). Hooks, shackles, or cable slings canbe used to attach guy lines. A pile should beconsidered driven to refusal when fiveblows of an adequate hammer are requiredto produce a total penetration of ¼ inch orless.

e. Concrete piles. Required driving re-sistances for prestressed concrete piles areessentially the same as for steel piles. Drivingstresses should be reduced to prevent piledamage. The ram velocity or stroke should bereduced during initial driving when soilresistance is low. Particular attention shouldbe paid to the following.

(1) Cap or helmet. The pile-driving cap orhelmet should fit loosely around the piletop so the pile may rotate slightly withoutbinding within the driving head.

(2) Cushioning. An adequate cushioningmaterial must be provided between thehelmet or driving cap and the pile head.

FM 5-134

FM 5-134

Three or four inches of wood cushioningmaterial (green oak, gum, pine, or firplywood) are adequate for piles less than50 feet in length in a reasonably goodbearing stratum. Cushions 6 inches thickor more may be required when drivinglonger piles in very soft soil. The cushionshould be placed with the grain parallel tothe end of the pile. When the cushionbecomes highly compressed, charred, orburned, it should be replaced. If driving ishard, the cushion may have to be replacedseveral times during the driving of a singlepile.

f. Special problems. Special problems mayarise when driving various types of piles. Alist of potential problems, with possiblemethods of treatment, is shown in table 4-1.

4-7. Aligning piles.

Piles should be straightened as soon as anymisalignment is noticed during the driving.When vertical piles are driven using fixedleads, plumbing is not a matter of concernsince the leads will hold the pile and correctthe alignment. Vertical piles normally shouldnot vary more than 2 percent from the plumbposition.

a. Checking misalignment. Along mason’slevel is useful in plumbing the leads. Forbatter piles (figure 4-10) a plywood templatecan be used with the level. Exact positioningis easier if the driver is provided with aspotter or moon beam.

4-12

FM 5-134

4-13

FM 5-134

b. Checking misalignment by cap re- alignment. The alignment can be checked bymoval. If the pile is more than a few inches lifting the cap from the pile butt. The pile willout of plumb during driving, an effort should rebound laterally if not properly aligned withbe made to restore the pile to its proper the leads and hammer.

4-14

FM 5-134

c. Aligning with block and tackle. Duringdriving, a pile may be brought into proper

H-piles, this procedure may induce un-desirable twisting and should be avoided if

alignment by using block and tackle (figure4-11). The impact of the hammer will tend to

possible. Jetting either alone or with thepreceding method, may be used.

jar the pile back into line. In the case of steel

4-15

FM 5-134

4-8. Obstructions.

Obstructions below the ground surface areoften encountered during pile-drivingoperations. Obstructions may result fromfilling operations in the area or from oldstumps or tree trunks buried by later deposits.Obstructions are frequently encounteredwhen piles are driven in industrial andcommercial areas of older cities or alongwaterfronts. They are a matter of concernsince they can prevent a pile from penetratingenough to provide adequate load-carryingcapacity. Piles are frequently forced out ofline by obstructions and may be badlydamaged by continued driving in an effort tobreak through the obstruction.

a. Driving. When an obstruction such as arotten log or timber is encountered, 10 or 15extra blows of the hammer may cause the pileto breakthrough (figure 4-12, 1). With steel orprecast concrete bearing piles, extra blows ofthe hammer may break or dislodge a boulder(figure 4-12, 2); however, care must be takenthat blows do not damage the pile. Pilealignment should be watched carefully duringthis operation to insure that the lower portionof the pile is not being deflected out of line.

b. Using explosives. If the obstructioncannot be breached by driving, the pile shouldbe withdrawn and an explosive chargelowered to the bottom of the hole to blast theobstruction out of the way (figure 4-12, 3). Ifusing explosives is not practical, the pile canbe left in place, and the foundation plan canbe changed to use other piles.

c. Jetting. Jetting is particularly valuable insoils which will settle firmly around the pile.Sands, silty sands, and some gravels provideconditions suitable for jetting as drivingthrough these materials in a dense stateresults in pile damage. Displacement piles incohesionless soils are frequently placed byjetting.

(1) Hose and pipe jetting. Jetting isperformed by inserting the jet pipe to thedesired depth, forcing water through thepile to loosen the soil, then dropping thepile into the jetted hole and driving the pileto its resistance. If the pile freezes beforefinal embedment, jetting can be resumed.Jetting should not be deeper than 4 or 5 feetabove final grade.

(2) Attached jetting pipes and hoses.Jetting for timber, steel, or standardprecast concrete piles is usually done by anarrangement of jetting pipes and hoses.The jet pipe is connected with a flexiblehose and hung from the boom or the piledriver leads. When possible, two jet pipesare lashed to opposite sides of the pile.Usually the pile is placed into positionwith the hammer resting on it to giveincreased weight, and the jet is operated sothat the soil is loosened and displacedevenly from under the tip of the pile (figure4-13). A single jet, however, is not workedup and down along the side of the pile, asthe pile will drift in that direction. Properuse of jet pipes is shown in figure 4-14.

(3) Special precast concrete jetting. Tofacilitate jetting, jet pipes can be embeddedinto precast concrete piles, Jetting ar-rangements for precast concrete piles areshown in figure 4-15.

(4) Precautions. Where piles must be drivento great depths, the double water jets maybe insufficient. Additional compressed aircan be effective. For combined water andair jetting, the simplest method is to tack-weld a small air pipe to the outside of thewater-jet pipe. In any jetting operation, thealignment of the pile is critical. Jetting is auseful method to correct the alignment oftimber piles in a pile bent (figure 4-16).Jetting around a pile while it is beingdriven is undesirable as the pile will driftoff line and location. Pile tips must be well

4-16

FM 5-134

4-17

FM 5-134

4-18

FM 5-134

seated with reasonable soil resistance 4-9. Predrilling.before full driving energy is used. Theultimate bearing capacity of the pile is It may be necessary to predrill pilot holes ifgenerally not significantly affected by the soils above the bearing stratum arejetting. However, jetting will greatly re- unusually stiff or hard. Predrilling keeps theduce the uplift capacity of a pile. preservative shell of treated timber piles

4-19

FM 5-134

intact. Predrilling also reduces underwaterheave and lateral displacement of previouslydriven adjacent piles. Holes are drilledslightly smaller than the diameter of the pileand to within a few feet of the bearingstratum. The pile is inserted, and the weightof the hammer forces the pile down near thebottom of the drill hole displacing any slurry.The pile is then driven to the requiredpenetration or resistance.

a. Rotary equipment. Predrilling should bedone with wet rotary equipment which leavesthe hole filled with a slurry of mud. Themethod employs a fishtail bit that contains awater jet within the drill stem. The water anddrill cuttings form a slurry which lines thewalls and stops sloughing of unstable soillayers. Additives (such as bentonite) can alsobe used to stabilize the walls of the drill hole.

4-20

FM 5-134

4-21

FM 5-134

b. Augers. Augers which remove all materialfrom the hole can cause a quicksand action.Sand or soil may flow into the drilled holebelow the water table. Augers should be usedonly above groundwater tables and in soilswhere a drill hole will stand open withoutcollapsing.

4-10. Special placement techniques.

a. Spudding. Spuds can penetrate debris orhard strata so the pile can reach the bearingstratum. Spuds consist of heavy pile sections,usually with special end reinforcement. Whenheavy piles (such as steel or precast concretepiles) are driven, the pile may be raised anddropped to break through a layer of hardmaterial or an obstruction. In a similaroperation, a pilot pile is withdrawn, and thefinal pile is driven in the hole.

b. Jacking. A pile may be jacked intoposition. This method is usually used when itis necessary to underpin the foundation of astructure and headroom is limited or whenvibration from conventional driving coulddamage an existing structure. The pile isjacked in sections using a mechanical orhydraulic screw jack reacting against theweight of the structure. The pile is selected forthe specific situation, and it is built up inshort, convenient lengths.

c. Vibrating. High-amplitude vibrators areused for driving piles in saturated sand andgravels, Vibratory hammers are particularlyadvantageous for driving sheet piling.

4-11. Driving piles in water.

a. Positioning piles. When piles are drivenin water, different methods may mark thedesired pile positions. When a number ofbents are to be constructed, a stake is placedat each abutment approximately 6 inchesfrom the pile centerline (figure 4-17). A wirerope is stretched between the two stakes, and

a piece of tape or cable clip is fastened to therope at each pile bent position. Piles are thendriven at each tape or cable clip.

b. Using floating pile drivers. When afloating pile driver is used, a frame forpositioning piles may be fastened to the hull.A floating template is sometimes used toposition piles in each bent (figure 4-18).Battens are spaced along the centerlinedesired for each pile. The battens are placedfar enough apart so that, as the pile is driven,the larger-diameter butt end will not bind onthe template and carry it underwater. If thepiles are driven under tidal water, a chain orcollar permits the template to rise and fallwith the tide. If the ends of the battens arehinged and brought up vertically, thetemplate may be withdrawn from betweenthe bents and floated into position for thenext bent provided the pile spacing is uniform.

c. Using floating rigs. If a floating rig isavailable, it can be used to drive the piles foran entire structure before the rest of the work.In general, more piles can be driven per man-hour with floating equipment because thedriver is easily moved. As soon as the piles inone bent have been driven, the rig may bepositioned to drive the next bent, while thebent just driven is braced and capped.Floating pile. driver rigs are difficult toposition where currents are strong andadequate winches are unavailable. Otherwise,they can be positioned easily either end-on orside-on to the pile bent which is being driven.Batter piles can be driven in any desireddirection by adjusting the spotter or catwalk,without using a moon beam.

d. Driving from bridge or wharf. Whenpile driving uses mobile equipment operatingfrom a deck of a bridge wall structure, twoprocedures may be used in moving the piledriver forward.

(1) Walking stringer method. As each bentis driven, the piles are aligned, braced, cut,

4-22

FM 5-134

and capped. The movable stringers aremade by placing spacer blocks betweentwo or three ordinary stringers so thedriving rig can advance into position todrive the next bent. The movable stringersare laid onto the bent which has just beencompleted. When the advance row or rowsof piles have been braced, cut, or capped,the pile driver picks up the temporarystringers behind and slings them into placeahead. The installation of permanentstringers and decking follows behind thepile driver. Variations of this method arepossible when a skid-mounted piledriver isused. This method gives the pile driver lessidle time than the method described in (2)following. Since the decking operationsare completely separate, individual crewscan be developed to drive, cut, cap, anddeck. These crews become more proficientand are more rapid than crews that work

at all three operations. This is hazardousbecause the machinery is supported byloose stringers and decking. Skill andorganization are required because severaloperations may be in progress at the sametime. Piles must move through the deckingcrews to reach the driving point, soplanning is important.

(2) Finish-as-you-go method. Instead ofusing movable stringers, each bent orbench, including the permanent stringersor decking, may be completed before therig is moved forward. This method is saferand requires less organization, since oneoperation follows another. The pile drivermay be idle or set stringers. To completeeach panel, personnel rotate jobs.

e. Driving from temporary earthcauseways. An excellent method for driving

4-23

FM 5-134

4-24

FM 5-134

piles for a bridge or wall structure in shallowwater is to extend a temporary earth causeway from the shore. Piles may then be drivenusing a mobile rig operating on the causeway.In the usual case, piles are driven through thefill. This is the fastest method of buildingbridges and other structures, where heightlimitations permit and required penetrationsare not unusual.

f. Driving from the 50-ton standardtrestle. Used in depths up to eight feet, thistrestle can drive two or three times as manypiles as a bridgemounted trestle. This methodinvolves constructing the bays (supportstructures) and using them as a platform.After completing a pile bent, a pile driverwalks the standard trestle by striking the baynearest the completed work, swinging it, andre-erecting it ahead.

g. Aligning. When all piles in a bent havebeen driven, they can be pulled into properposition with block and tackle and analigning frame (figures 4-19, 4-20). Bracingand subsequent construction of pile bents aredescribed in TM 5-312.

4-12. Driving underwater.

It is sometimes necessary to drive pilesunderwater rather than use a pile follower.Special pile hammers are designed for drivingunderwater. Recommendations by themanufacturer should be followed in preparingand rigging the hammer for underwaterdriving. Diesel hammers cannot operateunderwater.

4-13. Pulling piles.

Piles split or broken during driving or drivenin the wrong place ordinarily should be pulled.In some cases, it may be necessary to pullpiles to clear an area. Sheet piles and,occasionally, bearing piles that have beendriven for a temporary structure may be

salvaged by pulling. Piles should be removedas soon as possible, since the resistance topulling may increase with time. Commonmethods for pulling piles are described below.

a. Direct lift. If a pile is located so that acrane of substantial capacity can be moveddirectly over it, pulling by direct lift ispossible. A sling should be wrapped aroundthe pile and the pull steadily increased untilthe pile begins to move or is extracted. Jettingcan be used to help loosen a pile. The boomshould be snubbed to a stationary object tokeep it from whipping back if the pilesuddenly comes loose or the lifting tacklebreaks.

b. Hammer and extractor lift. Piles maybe pulled with air or steam-powered extractorsor with inverted acting hammers rigged forthis use. Vibratory hammers are effective.Usually, a 25-ton lift on the extractor will beadequate, but multiplereeved blocks in aderrick may be needed. If piles are difficult topull, additional driving may break them loose.Use a safety line at the tip of the boom in casethe connecting line or cable breaks.

c. Tidal lift. Piles in tidewater maybe pulledby attaching the slings to barges or pontoonsat low tide and allowing the rise of the tide toexert the lifting force. To keep barges fromtipping, a barge should be placed on eitherside of the pile; and the lifting force should betransmitted by girders extending across thefull width of both barges.

4-14. Pile driving in cold weather.

It is possible to conduct pile-drivingoperations in severe cold even though theground is frozen. Frost up to two feet thickcan be broken successfully by driving a heavypilot pile or a heavy casing. Ground can bethawed to a shallow depth by spreading alayer of several inches of unflaked lime overthe area, covering the layer with snow, then

4-25

FM 5-134

with a tarpaulin, which in turn is coveredwith snow. This method will melt a layer offrost 3 feet thick in 12 hours. Earth augers areeffective in drilling holes in frozen groundand may aid pile driving. Holes cut in soundriver ice act as guides for piles for bridgefoundations. Auxiliary equipment such as asteam or air hammer and other machineryrequire special handling in cold weather.

Instructions furnished by the manufacturermust be carefully followed.4-15. Pile installation in permafrost.Construction operations under arcticconditions and in permafrost areas arediscussed in TM 5-349. Pile installationmethods in permafrost include steam or waterthawing, dry augenng, boring, and driving.

4-26

FM 5-134

4-27

FM 5-134

a. Steam or water thawing. Piles can beinstalled in permafrost by prethawing theground with steam points or water. Steam at30 psi delivered through a l-inch steel pipe issatisfactory for depths up to 15 or 20 feet. Forgreater depths, higher steam pressure (60 to90 psi) and larger pipes (2-inch) are used.Water jetting is used if the soil is sandy. Thepile is hammered lightly into the ground, andthe steam aids the penetration while

scaffolding or an A-frame facilitates handlinglong sections of steam-jetting and water-jetting pipes. The steam demand is ap-proximately 15 to 20 cubic feet per foot ofpenetration. When the final depth is reached,the steam point is kept in the hole to make thehole big enough to accept the pile. If the soil issandy, the steam point is kept in place for ½hour; if the soil is clay, it may remain for upto 3 hours. Figure 4-21 shows the approximate

4-28

FM 5-134

shape of the hole thawed in sand-silt soilafter 1½ hours of stem jetting.

(1) Setting the pile. After the hole has beenthawed properly, the pile is placed by theusual methods. After three to four days ofthawing, a series of piles may be set (figure4-22). Wooden piles have a tendency tofloat when placed in the thawed hole andtherefore must be weighted or held downuntil the permafrost begins to refreeze.

(2) Disadvantages. Steam or water thawinghas the disadvantage of introducing somuch heat into the ground that freeze back

may be indefinitely delayed. Piles may notdevelop adequate bearing capacity, or-hostheave may work them out of the groundand damage supported structures. Steamor water thawing should not be used inareas where the mean annual permafrosttemperature is greater than 200F. Thismethod may be used in colder permafrostonly with exceptional precautions tocontrol heat input into the ground if othermethods of installation are not possible.

b. Dry augering. Pile holes maybe drilledin the permafrost using earth augers withspecially designed bits for frozen ground.

4-29

FM 5-134

Holes 2 feet in diameter can be advanced atrates of up to about 1 foot per minute in frozensilt or clay, depending on the type of bit,ground temperature, and size of equipment.Holes up to 4 feet or more in diameter can bedrilled readily in such soil. Drilling with anauger is the easiest method when the frozenground surface permits ready mobility andsteam and water do not have to be handled.This method is not feasible in coarse, frozensoils containing boulders.

(1) Hole drilling. The holes maybe drilledundersized, and wood or pipe piles maybedriven into the holes. However, the holesusually are drilled oversized; and a soil-water slurry is placed in the annulus’ spacearound the pile and allowed to freeze back,effectively transferring the imposed pileloads to the surrounding frozen soil.

(2) Slurry. Silt from a borrow pit or fromthe pile hole excavation can be used forslurry as can gravelly sand, silty sand, orplain sand. Clays are difficult to mix andblend, and when frozen they are not strong.Gravel, unsaturated soil, water, or concreteshould not be used for backfill in permfrostareas. Organic matter must not be used inslurry. Details on dry augering are con-tained in TM 5-852-4.

c. Boring. Holes for piles may be made byrotary or churned drilling or by drive coring(under some conditions) using various bitsand drive barrels. Frozen materials areremoved with air, water, or mechanicalsystems. Procedures are the same as for dry-augered holes.

d. Driving. Conventional or modified piledriving procedures, including diesel andvibratory hammers, may be used to driveopen-ended steel pipe and H-piles to depthsup to 50 feet or more in frozen groundcomposed of silty sand or finer-grained soilsat ground temperature above 25°F. Under

favorable conditions heavy pipe and H-pilescan be driven into the ground at lowertemperatures. Freeze back is complete within15 to 30 minutes after driving. The H-piledriven in frozen soil should not be smallerthan the HP 10 x 42, and the rated hammerenergy should not be less than 25,000foot-pounds.

4-16. Cutting and capping of piles.

a. Timber piles. The capping of timber-pilebents should bear evenly on every pile in thebent. The piles should be cutoff accurately byfollowing sawing guides nailed across allpiles in the bent (figure 4-23). After the pilesare cut and treated with preservatives, thecap is placed and fastened to the piles by driftpins driven through holes bored from the topof the cap into each pile. If a concrete cap isused, the tops of timber piles should be cutsquare, treated with preservative, andembedded in the concrete at least 3 inches.

b. Steel piles. Steel-pile bents are cut to theproper elevation using a welding torch. Aworking platform and cutting guide fastenedwith C-clamps can be used for this purpose(figure 4-20). Capping of steel piles with steelmembers follows the same procedure asoutlined for timber piles, but the members arejoined by welding or riveting, and steel platesare used rather than timber splices or scabs.If the cap is reinforced concrete, the top of thepile should be embedded at least 3 inches inthe concrete. A well-designed reinforcedconcrete pile cap does not require steel platesto transmit a compressive load to H-piles. Ifthe piles are subject to uplift, cap plates oradditional embedment is required.

c. Concrete piles. Cutting concrete pilesrequires concrete saws, pneumatic hammers,and an acetylene cutting torch. A V-shapedchannel is cut around the pile at the level ofthe desired cutoff. Reinforcing bars areexposed and cut with the torch at the desired

4-30

FM 5-134

4-31

FM 5-134

point above the cutoff. If possible, thereinforcing bars should project into a concretecap for bonding. The head of the pile can bebroken off by wedging or pulling with a linefrom a crane. The cap is placed on top of thepiles by casting in place or drilling groutholes at the proper position in a precast cap.Another suitable method is to drill holes andto grout in bolts or reinforcing steel,depending on the type of cap used.

d. Anchorage. The uplift force on a structureis transmitted to the pile by a bond betweenthe pile surface and the concrete of the pilecap, or by a mechanical anchorage. Theultimate bond between concrete and freshly-embedded timber piles may be 60 psi or more;however, long submergence may cause somedeterioration of the outer layer of wood whichreduces the bond value. When the embeddedportion of timber piles is submerged, aworking stress for a bond of not more than 15psi should be used without considering theend surface of the pile. When the load intension is greater than the strength whichcan be developed by the bond, a mechanicalanchorage can be used. The resistance of awood pile to extraction from concrete maybeincreased by notching the embedded portionof the pile and considering the longitudinalshearing strength of the timber.

Section III. PREPARATION AND USEOF PILES

4-17. Sheet piles.

a. Alignment. When sheet piles are drivenas permanent structures, such as bulkheads,the first pile must be driven accurately,maintaining alignment throughout. Atimber-aligning frame composed of doublerows of studs, to which one or two rows ofwales and diagonal bracing are spiked, maybe required to maintain alignment, in softsoils. Normal practice is to drive the ball endof interlocking steel sheet piles to prevent soil

from being trapped and forcing theinterlock open during driving.

b. Steel sheet piles. Interlocking steel sheetpiles can be driven by one of two basicmethods.

(1) Single pile or pair of piles. In thismethod the driving leads must be keptvertical and stable, with the hammercentered over the neutral axis of the pile.This requires a firm, level foundation forthe driving equipment.

(2) Preassembled sheet piles. The pilingand wall are formed and driven along theline. The piling is set with both axesvertical. Vibration in the hammer or thepile will drive the piles out of alignment.Z-piles are driven in pairs. Single or pairsof short piles are driven to full depth in softground to prevent creep. Long piles aredriven into the ground as follows.

Set waling along the line of sheeting.

Drive a pair of sheet piles to part depth.

Set a panel of a dozen single piles or pairsin the walings.

Drive the last pile or pair in the panel partway.

Drive the piles between the first and lastpile or pairs of piles to full depth.

Drive the first pile to full depth.

Drive the last pile two-thirds its fullpenetration to act as a guide for the firstpile of the next panel.

c. Concrete sheet piles. Concrete sheetpiles are frequently placed by jetting. If awatertight wall is required, the joints aregrouted after driving is completed. The soil at

4-32

FM 5-134

the bottom of the pile is slushed out by a has been drawn down, an additional lengthwater jet pipe of sufficient length to reach the is usually welded on rather than attemptingbottom of the pile. A tremie is used to placegrout underwater. Flexible fillers such asbituminous material may be placed in jointsat intervals of 25 to 50 feet. If a cap is placedon the sheet pile wall, the flexible jointscontinue through the cap. In reinforcingpreviously driven sheet piles, frictional dragmay occur. To counteract this, the piles maybe bolted or welded to a stiff waling. If a pile

to jack up the pile.

4-18. Drilled piles.

Power-driven earth augers are used to drillholes to the size and depth required (figure4-24). Commercial drilling rigs are availablein a wide variety of mountings and drivingarrangements. If the holes remain open and

4-33

FM 5-134

dry until concreting is completed, thefoundation can be constructed rapidly andeconomically. If the walls of the hole areunstable and tend to cave in, the hole maybeadvanced using a slurry, similar to drillingmud alone or in combination with casing.

a. Slurry. Slurry is a mixture of soil,bentonite, and water which forms a heavy,viscous fluid mixed by lifting and loweringthe rotating auger in the hole. When theslurry obtains the proper consistency, thehole is advanced through the cohesionlesszone using the auger. The slurry stabilizesthe wall of the hole, preventing inflow ofgroundwater. Slurry is added at the bottom ofthe hole as depth is advanced.

b. Dry hole. If the hole is dry, the concrete isallowed to fall freely from the ground surface.The cement and aggregate may separate ifthe concrete falls against the sides of theshaft. If the diameterie small, a short, verticalguide tube is located at the center of the top ofthe shaft where the concrete is introduced.Reinforcement may be provided through acircular cage inside which the concrete canfail freely. A slump of about 6 inches issuitable under most conditions. Higherslumps are used in heavily reinforced piers.The presence of even a small amount of waterin the bottom of the shaft may reduce thestrength of the concrete. Bags of cement aresometimes laid on the bottom to absorb theexcess water before the concrete is placed.Tremied concrete can be placed in an uncasedslurry fill hole; however, refined techniquesand experienced specialist contractors aremandatory.

4-19. Shell-type piles.

In shell-type, cast-in-place concrete piles, thelight steel casing remains in the ground andis filled with concrete after it has beeninspected and has been found free of damage(figure 4-25).

4-34

Section IV. SUPERVISION

4-20. Manpower.

The size of the pile-driving crew dependsupon a number of variables: equipmentavailable; type, length, and weight of pilesbeing driven; and driving conditions. Theminimum crew is 5 in most situations. Indriving light timber piles with a drop hammeror a crane fitted with pile-driving at-tachments, 1 person would be needed as asupervisor, 1 as a crane operator, and 3 ashelpers in handling the piles and hammer.One person should serve as an inspector,recording blow counts and penetrations. Acarpenter may be needed to cut off the piles. Alarger crew is required to drive long, steelbearing piles under hard driving conditions.If a steam hammer is used, a boiler engineerand fire fighter will be required. If anadditional crane or winch is needed to placethe piles into position, additional personnelare required. A welder may be needed to cutoff the piles at the correct elevation or to weldon additional sections. The crew may consistof 10 to 12, including supervisors and 4 or 5laborers.

4-21. Productivity.

The rate at which piles can be installeddepends upon many factors, such asequipment, length and weight of the piles,and driving conditions. A normal-sized crewcan install from 1 ½ to 5 timber bearing pilesper day (day operations) and from 3 to 6 steelsheet piles per hour. Figures for pile-drivingoperations can be established from experiencewith a particular crew, equipment, piles, anddriving conditions.

4-22. Safety.

a. Safety precautions. Standard safetyand accident prevention procedures developedfor general construction operations also apply

FM 5-134

4-35

FM 5-134

to pile-driving operations. Pile driving is ahazardous operation, and adequate care mustbe taken to protect personnel from injury.

Proper individual protective equipment(shoes, gloves, helmets, and ear plugs)should be worn at all times. All equipmentguards should be maintained and in place.

Cooperation between equipmentoperators and personnel is essential toavoid accidents. Hand signals must beused during pile installation operations(figure 4-26).

Personnel must be kept clear when pilingis being hoisted into the leads and duringthe first few feet of driving. Mill scale, forexample, may be driven off a steel pileduring driving.

Operators must never stand under ornear a pile hammer. If an y adjustment is tobe made at or below a hammer, the hammershould be stopped and rested on a pile orsecured by placing the hammer-retainingpin through the pile leads. Ladders shouldbe provided on frames and leads to giveaccess to the hammer.

All equipment, particularly pile leads,must be examined frequently for any cracksor loose bolts.

Diesel pile hammers must be cleanedregularly to avoid an accumulation ofdiesel oil which may become a fire hazard.They should be fitted with a trip wire orrope so that the hammer can be stoppedfrom ground level and workers do not haveto climb ladders to operate the fuel cutoff.

The exhaust of steam hammers must becontrolled so that workers are not en-

dangered by discharges of steam orscalding water. All hoses and hoseconnections must be in good condition andproperly secured to the hammer inlet. Theend of the hose must be tied to the hammerto prevent a flying end if the connectionshould break loose.

Helmets, driving caps, anvil blocks, andother parts receiving impact must beinspected regularly for damage or fracture.Worn parts should be replaced before wearbecomes excessive, and particular caretaken to avoid wear that will develop astress concentration on a moving part.

The hammer must be kept at the bottomof the leads whenever possible.

b. Handling procedures. Creosoted timberscan cause skin bums. When creosoted pilesare driven, a fine spray is created when thehammer strikes the pile. This material on theskin should be washed off immediately withsoap and water. Cream or lotion maybe usedto protect the skin from creosote. Gogglesprotect the eyes. Hand and power tools usedto prepare piles for driving and to cut off,straighten, and align piles after they aredriven must be used safely. When it isnecessary to cut off the tops of driven piles,piledriving operations should be suspendedexcept when the cutting operations are locatedat least twice the length of the longest pilefrom the driver.

c. Water procedures. If piling is carried outover water, workers should wear life jackets.Life belts with a suitable length of cordageshould be available on the attendant floatingcraft.

4-36

FM 5-134

4-37