In recent years, the construction and civil engineering industries have seen a quiet revolution in how concrete piles are cropped, with hydraulic pile croppers now becoming the "must-have" equipment on sites and projects throughout the world.

In-situ concrete piles have been and are used for various civil engineering and construction structures, with common applications ranging from small housing developments to major inner-city renovation, construction and infrastructure projects, such as HS2. These mass-produced piles are customisable length-wise, being suitable for a huge range of applications and ground conditions, thereby offering a cost-effective precision piling solution once reduced.

In years gone by, concrete piles were reduced using methods such as hydraulic or diesel hammers and other inaccurate, expensive and emission-producing methods. These outdated methods risked damaging the integrity of the piles and gave rise to associated health problems such as HAV (Hand Arm Vibration syndrome) and the very real risks associated with manual work within unstable/subterranean ground conditions. As a result, hydraulic pile breakers were developed to make the task of reducing these piles safer and more efficient.

The first major steps in producing the pile croppers that we know today began in the ‘90s, with the development and refinement of the pile cropping technology being undertaken by members of the current National Pile Croppers' (NPC) team.

This development work increased the reliability, safety and cost-effectiveness of the equipment over a period of over 20 years. In later years, new equipment has been developed for the various types of piles and applications that are found within the global construction industry.

The work undertaken by concrete pile cropping experts at NPC, in particular, led to a set of pile cropping standards being incorporated into the Health and Safety Executive's Guide of Current Practice. The new generation of pile croppers have also been widely advocated by health and safety professionals and engineers alike. As a result, hydraulic pile croppers have become essential in making the task of reducing piles much safer and more efficient.

What is a pile cropper?

A pile cropper (also known as a pile cutter or pile breaker) is essentially a very precise hydraulic shear with defined angles of deflection and points of contact ensuring a clean cut of the excess that does not interfere with the efficacy of the remaining pile.

There is a breadth of different types and sizes available, depending on the task at hand. For example, augured, bearing, contiguous, secant, CFA, trench and helical displacement with croppers are available in varying sizes ranging normally from 300mm to 1200mm in diameter.

Mounted on a 360-degree excavator via quick-release fittings, pile croppers have proved their versatility and effectiveness in all sectors of the construction industry, from housing to commercial, public to private, utilities, road and rail. When lowered onto the concrete pile, the hydraulic system operates the jaw(s), which allows the pile cropper to cut a de-bonded pile (de-bonding foam or Isofoam is a de-bonding tube that is installed on the projecting bars of a pile cage to prevent the concrete adhering to the reinforcing bars) and cause the concrete to break away leaving a horizontal finish as a result. In doing this, the chisels penetrate in a precise direction up to the rebar to make the fracture.

On bonded (where no de-bonding is used the reinforcement will bind with the concrete) piles, the chisels will penetrate further, and due to the shape of the chisels and the reaction forces of the rebar, the concrete will break in pieces and can easily be lifted off the pile enabling recycling of the cut away concrete.

Using a cropper

The connection between the excavator and the pile cropper is made via quick-release fittings on excavators (generally ranging from 6t to 21t, although pile croppers exist for smaller and larger jobs to be fitted on small and large carriers) with both flow and return being required with pressures ranging from 150 bar to 275 bar.

The excavator lifts the pile cropper over the pile and addresses the pile cut off level where a complete horizontal fracture is made. The chisels penetrate in a horizontal direction up to the re-bar to make the fracture. On bonded piles, the chisels will then penetrate further, and due to the shape of the chisels and the reaction forces of the reinforcement, the concrete will break into pieces and can easily be lifted off the pile.

When using a pile cropper, it is advised that the piles should be set or cast higher (again in-situ) than the desired finish level. This is to ensure that any impurities or damage at the top of the pile is removed as part of the cropping process. In addition to this, it is important to consider how much protruding reinforcement is required to allow for the continuation of the construction phase.

In order to avoid damage to piles during cutting, it has been found to be important to ensure that the right type of cropping equipment is chosen. This is something that is essential for a successful pile-cutting project, especially when specific time frames need to be considered (National Pile Croppers, for example, has a trained and experienced in-house help desk that advises users of how to get the best results).

A common problem often experienced is when fracturing or spalling occurs beneath the surface of the concrete. This is something that is very frustrating and time-consuming for construction teams to put right, as well as expensive from a financial point of view. Therefore, damage to piles should be avoided at all costs, which is something that using the correct pile cropper for the job can help to avoid.

Advantages of using a hydraulic pile cropper

• Considerably faster than conventional methods being able to crop up to 100 piles per day

• Very compact dimensions

• Low cut-off level

• Easy to operate

• No noise, no vibrations

• No cracks below cut level when used with reinforced de-bonding methods

• The reinforcement remains fully undamaged and intact

• Leaves a perfect horizontal concrete fracture at pile cut off level

• Easy adjustment

• Complies with health and safety guidelines for hand-arm vibration injuries