Silent Piling Brochure

REVISED SILENT PILING BROCHURE

The introduction of Japanese piling presses into the UK in the early 1990s brought a much needed method of sheet pile installation that produced minimal vibration, very low noise levels and could cope with the variable soil strata encountered. Combined with pre-augering the soil in advance and water jetting as the pile was installed, the UK construction industry was at last able to offer clients a means of sheet pile installation with minimal disturbance to the surrounding environ.

Berryrange Ltd owns and operates two WP150 silent and vibration free pilers and the JZ100 Zero Piler, (only one in Europe), complete with their own purpose built AOKI water jetting units. One power pack is self propelled giving additional versatility and independence from craneage. Our ABI leader rig is equipped with an auger motor and bit specifically designed for pre-augering the soil when dense granular stratas are encountered.

The piler operates on a pitch and drive basis.  A pile is fully driven before the machine can move forward to drive the next pile.

The first three piles are installed by using a reaction stand placed on a firm level area, 5m x 5m in plan, and 500mm below the finished pile head level.  The stand is loaded with steel kentledge or sheet piles to provide a weight the piler can react off.

The piler is clamped to the stand and reacts off the dead weight to push in the first pile.  The next pile is then pushed in by reacting off the kentledge and an amount of skin friction and/or adhesion developed on the first pile.  By the time three piles have been driven the piler is clear of the reaction stand (the stand can be removed) and sufficient reaction has been developed from three piles to enable the machine to move forward driving piles.

The piler can also start off previously installed or conventionally driven piles.

The self-moving process enables the piler to walk along the top of the previously driven piles. Craneage is only needed to support the piler as it moves when insufficient reaction or bearing capacity is available.  This is generally associated with short piles, weak soils or when the pile tops are high above ground level. Generally, a smaller crane is all that is needed, once started, to lift a pile into the piler.

The piler is made up of two main components.  A lower section which contains the clamping legs and an upper section that houses the pushing mechanism.  The upper section slides on the lower section.  This is important as it enables two piles to be installed from the one position.

The upper body of the piler also rotates in a horizontal plane independent of the base section.  This allows the machine to install piles up to 90° either side of the pile line, and enables it to turn corners unaided.  Piles are driven outside the pile line to negotiate the corner and are referred to as dummy piles.  They can be extracted once the corner is negotiated if craneage is available.  If the piles are to be extracted at a later date the dummy piles are left in place to enable the corner to be re-negotiated.

Curved piling can be installed if required as well as a gradual change in the top level of the piles.  A step up of 100mm and down of 50mm is possible per pile.

Piles can be pushed into most soils, but each soil requires a different technique.

It must be remembered that if reaction cannot be achieved the pile cannot be driven.

Clays, silts and fine sands are the most compatible soils for driving through.  Gravels can present difficulties due to high end bearing resistance being generated and the need to displace individual particles.  Gravels can be driven through but will not offer sufficient reaction alone.  Therefore penetration into another layer where reaction can be generated will generally be required.

Several techniques are available to overcome problems and achieve pile penetration.

The introduction of high pressure water jetting enables a pile penetration to be pushed into granular soils.  A 2” diameter jetting lance is temporarily secured into the pan of the pile with the nozzle just above the end of the pile. Once the pile is pitched into the Tosa, water is delivered through the lance and into the ground.  The soil is disturbed locally and reduces the driving resistance thus allowing pile penetration. The ground reconstitutes itself once jetting ceases. This is demonstrated by reaction being generated on the piles once driven. The flow is monitored and regulated by the piler operator.  Water flow is maintained throughout the driving cycle to prevent damage to the nozzle.  In clays, silts and fine sands the water acts more as a lubricant to regulate the amount of adhesion generated.  A minimum supply of 75 gallons per minute is usually required.  This is discharged into a skip from which the jetting unit draws it.  The use of a skip enables a reservoir to be built up to draw down as required.  Under normal circumstances water arising from the jetting process dissipates into the surrounding strata.

Where dense granular stratas are encountered soil disturbance by an auger mounted on our leader rig in advance of pile driving can reduce the resistance in the ground and enable pile penetration.  Holes are drilled at intervals along the pile centerline where the pile clutches interlock.

Further reduction in resistance is achieved by applying a hot applied bituminous sealant, to the lead clutch of a pile.  This prevents granular particle clogging the open clutch, which would otherwise require a force to displace the material from the clutch.

For extracting piles the piler simply works in reverse, walking backwards along the pile line, and negotiating corners.  The reaction stand is used at the end to retrieve the piler, or the last three piles can be sacrificed if there is insufficient room to set up the stand.

The ability to walk backwards means that if the WP150 piler cannot be lifted from a pile run once installed, due to a lack of access for craneage, the machine can walk back along the installed pile line to the start, where it can be recovered.

The WP150 Piler is ideal for installing piles adjacent to properties or boundaries. An offset of 800mm from the pile centre line to a structure or boundary can usually be achieved. At corners, extra space may be required for the dummy piles, and the rear of the machine to swing around.

Under certain circumstances, where space is a premium a special piler, The JZ100 Zero Piler, and pile section, SMJ Zero Pile, can be offered that can install a 200mm wide pile within 100mm of a structure or obstruction.

The legs of the piler protrude 500mm to grip the top of the piles.  Clearance is normally provided by digging a 500mm deep lead trench, thus economising on the pile length required.

Sudden changes in pile level are achieved by lifting off the piler, either cutting down three piles or welding on three pile extensions, and then replacing the piler.

The length and section of pile that can be driven is governed by factors other than the ground being driven into.  The need to develop sufficient reaction usually governs the minimum length.  The ability of the pile to withstand the driving force and loadings induced, particularly during the self-moving process, affects the minimum pile section.  The maximum pile length is dependent upon the driving force available from the piler and the resistance encountered.