What is the best pile cutting equipment to use?

In recent years the availability of various types of concrete pile cropping equipment has escalated considerably.

An ever-changing market has also seen the requirement for pile cutting equipment to evolve from the traditional hydraulic cropper machine to the range you now see National Pile Croppers Limited producing for the UK and Worldwide market.

Piling companies are using a multitude of differing concrete pile types and designs; prestressed and precast driven piles with a vast array of reinforcement (rebar) configurations which present groundwork contractors’ dilemmas for the best approach to reduction without causing costly damage and program delays.

Augured piles can be equally as challenging with tight sites becoming the norm and the use of contiguous and secant piled walls common place. It would be impossible to have a ‘one pile cropper suits all’ scenario making hiring a suitable concrete pile breaking machine the best option.

Maintenance, downtime and storage costs all adding weight to ownership being an expensive and unnecessary purchase.

Addressing Precast or square piles we find a number of complications when looking to reduce to form level. Final pile cut off levels are defined by the site structural engineer; piles will also be integrity tested either prior to or post reduction.

Reinforcement bars or rebar can range from T8 to T20mm and in number from 1 to 16 with varying amount of cover from pile edge. Pile sizes generally in the UK starting at 200mm up to 350mm.

We can see from these variables alone the scope for differing types of cropper and once we then consider number of piles, layout, excavator size and reduce levels we can see the potential for a number of potential pile cutting procedures to be adopted.

Projects with huge mega-warehouse structures formed on tens of thousands of pre-cast concrete piles requiring a pile cropper machine to speedily clear the sea of piles to ground level are common place; in this instance our new to market Power Cropper has been designed to cut through the rebar at 1m lengths or more leaving a class leading finish and ready for final reduction to form level.

At this point it may be the case that the power cropper continues to be used or a less aggressive cropper such as our multi-bar be used to prevent further spalling below this level.

Where excavator size is limited to 8T NPC use the Dual cropper which in most cases performs as the power cropper, however, at only 800kg and with a width of less than 600mm it becomes a very useful tool to manoeuvre around tight sites.

Another favourite for pre-cast piles is the Multi-bar cropper which some operators prefer due to its ‘softer’ nature, thus reducing the likelihood of reinforcement bars being damaged or ultimately broken requiring costly repair.

Multi rebar piles are often ‘scored’ at final pile cut off level to prevent spalling. Single reinforcement bar piles such as those installed predominately by Roger Bullivant and Van Elle being much easier to reduce to pile cut off level using our Single bar cropper.

Here concrete is quickly taken at small intervals of around 200-250mm; these piles are much easier to cut and generally leave a tidier finish.

Due to the nature of the pile joint system with single bar piles it is generally not recommended to use a power cropper which in some conditions can cause a joint to separate resulting in failed integrity testing and the potential of new pile being installed.

CFA augured or round piles present issues of a different type.

Pile layout and pile size being key elements to the choice of pile cutting equipment to be used. Generally, in the UK pile sizes range from 300mm diameter up to 1200mm diameter, however projects in our capital city London may have pile sizes in excess of 1500mm.

De-bonding of the reinforcement is now adopted by many piling companies and clients which increases greatly the productivity of pile reduction.

In essence the pile section to be removed can be greater in size and in most cases will also leave a finish requiring zero clean up, this though only if the de-bonding foam has been installed to the correct level and the reinforcement bars are straight and without tie wire.

CFA Piles may be installed in many different layouts such as normal bearing, trench, pile caps, contiguous and secant walls.

National Pile croppers have designed equipment to tackle each type, our knowledge and experience place us in a position to advise the client on best method and equipment from a very early stage in the design process.

Where room allows and on traditional CFA piles without de-bonding foam we recommend the use of traditional linked or modular CFA cropper type, this will penetrate into and past the reinforcement bars breaking the concrete into small pieces, unfortunately some trimming may be required to achieve required finish.

Should the pile head have ‘mushroomed’ the cropper will also require to be manually adjusted using extra links or half links.

For CFA piles with de-bonding foam installed our range of Quad croppers can be used, this cropper is very fast and accurate removing cut pile with its 4 powerful jaws and an excellent level finish with zero requirement for manual trimming, there is also zero requirement to manually change the cropper configuration within its specific range; excavator sizes from 13t and above.

Where CFA piles are in trenches or close proximity pile caps the NPC Contiguous cropper would be best suited, with its two opposing synchronised jaws and small overall footprint it is ideal for tight spaces, working best on de-bonded piles.

Secant piled walls will have intersecting piles

A secant piled wall will have intersecting piles, male (primary) piles with reinforcement and female (secondary) piles without – usually designed for the purpose of water retention.

There will subsequently be zero gap between adjacent piles which on first inspection would appear to make pile reduction impossible.

First option would be to remove the female pile using traditional methods (CP9 or small pecker), this then giving enough space for either traditional CFA/Quad/Contig cropper types to be used.

In some instances, we can simply use our contig cropper with one leg either side of the wall to remove both primary and secondary piles.

Contiguous piled walls are a closely spaced retaining wall usually installed with a gap of 150mm between adjacent piles. Unfortunately, from a pile cropping perspective this gap is rarely achieved due to pile overspill in loose ground conditions.

National Pile Croppers have worked tirelessly on our Quad and Contiguous croppers to give clients two options when pile spacing is reduced to around 50mm.

We also have options with special narrow links which can be attached to CFA linked croppers.

Another potential issue with piled walls can be the room available at the rear of the wall which can be tight on an adjacent building or structure, this limiting the options to get a cropper over the pile.

Again, NPC have options and have manufactured equipment to overcome this eventuality.

Displacement piles used in contaminated ground where spoil remains in the bore walls give a pile in the form of a screw thread, this presenting issues for a pile cropper which firstly will not sit square on the pile and secondly will struggle to penetrate the core and reinforcement cage.

The NPC Quad cropper has been built with this in mind and will successfully reduce piles of this type.

Speed and quality can effect overall project costs

Overall speed of the pile cutting procedure and quality of finish at pile cut off level can be directly related to overall project costs.

The NPC range of pile cropping equipment has all been extensively developed and tested to provide class leading finish at pile cut off level, in most cases negating the requirement for any manual trimming using traditional hand-held methods, this then removing costly man hours and reducing potential hazards such as Hand Arm Vibration.

The NPC range of concrete pile cutting equipment provides a clean controlled cut with minimal risk of damage to reinforcement bar; this utilising our specifically designed ‘synchronised and bladed jaws’ which unlike competitor offerings will not cause spalling subsequently giving rise to additional costs for the repair or replacement piles.

National Pile croppers stand out from the crowd, we understand that no two piled projects have the same requirements; we ensure the right questions are asked to ensure we provide the pile breaking machine to suit requirements. With our vast experience we deliver on each and every occasion.

National Pile Croppers are dedicated to keeping their finger on the pulse complimenting specific requirements with a range of concrete pile breaking equipment built for the 21st century.