Changing an industry: The rise of the hydraulic concrete pile cropper

In recent years, the construction and civil engineering industries have experienced a quiet revolution in how concrete piles are cropped. Hydraulic pile croppers have become the ‘must-have’ equipment on sites and projects across the globe. Lee Aston of National Pile Croppers explains what exactly a hydraulic pile cropper is and how to get the best from this innovative equipment.

In-situ concrete piles have long been used for various civil engineering and construction structures. Common applications range from small housing developments to major urban renovations and infrastructure projects, such as HS2. These mass-produced piles can be customised in length, making them suitable for a wide range of applications and ground conditions, offering a cost-effective, precise piling solution once reduced.

In the past, concrete piles were reduced using methods such as hydraulic or diesel hammers, which were inaccurate, expensive, and produced harmful emissions. These outdated methods risked damaging the integrity of the piles and led to associated health issues, such as Hand Arm Vibration (HAV) Syndrome, as well as the dangers of working in unstable or subterranean ground conditions. As a result, hydraulic pile breakers were developed to make the process of reducing piles safer and more efficient.

The first major steps in producing the pile croppers we know today began in the 1990s. The development and refinement of pile cropping technology were carried out by members of the current National Pile Croppers (NPC) team. Over a period of more than 20 years, these efforts significantly increased the reliability, safety, and cost-effectiveness of the equipment. In recent years, new equipment has been developed to meet the varying needs of the global construction industry.

The work of NPC’s concrete pile cropping experts led to the incorporation of pile cropping standards into the Health and Safety Executive Guide of Current Practice. These new-generation pile croppers have been widely endorsed by health and safety professionals and engineers. Consequently, hydraulic pile croppers are now essential tools for making the task of reducing piles both safer and more efficient.

Defining a Pile Cropper

A pile cropper (also known as a pile cutter or pile breaker) is essentially a precise hydraulic shear with defined angles of deflection and contact points that ensure a clean cut of the excess pile material, without interfering with the integrity of the remaining pile. There are a variety of pile croppers available, depending on the task at hand. For example, augured, bearing, contiguous, secant, CFA, trench, and helical displacement croppers are available in sizes typically ranging from 300mm to 1,200mm in diameter.

Mounted on a 360° excavator via quick-release fittings, pile croppers have demonstrated their versatility and effectiveness across all sectors of the construction industry, from housing to commercial, public to private, utilities, and road and rail projects. When lowered onto the concrete pile, the hydraulic system operates the jaw(s), enabling the pile cropper to cut a de-bonded pile (a pile with de-bonding foam or Isofoam to prevent the concrete from adhering to the reinforcing bars). This results in the concrete breaking away, leaving a horizontal finish.

In bonded piles (where no de-bonding is used and the reinforcement binds with the concrete), the chisels penetrate further, causing the concrete to break into pieces, which can easily be lifted off the pile for recycling.

Using a Hydraulic Pile Cropper

The pile cropper is connected to the excavator via quick-release fittings, with excavators typically ranging from 6t to 21t, though smaller and larger croppers are available for different jobs. Both flow and return lines are required, with pressures ranging from 150 bar to 275 bar. The excavator lifts the pile cropper over the pile, positioning it at the correct cut-off level where a complete horizontal fracture is made. The chisels penetrate horizontally up to the rebar to make the fracture. On bonded piles, the chisels penetrate further, and due to the shape of the chisels and the reaction forces of the reinforcement, the concrete breaks into pieces, which can then be lifted off.

It is advised that the piles be set or cast higher (in-situ) than the desired finish level. This ensures that any impurities or damage at the top of the pile are removed during the cropping process. Additionally, the amount of protruding reinforcement must be considered to ensure that the next phase of construction can continue smoothly.

To avoid damage during cutting, selecting the correct type of cropping equipment is essential for a successful pile cutting project. National Pile Croppers, for instance, offers a trained and experienced in-house help desk to assist users in achieving the best results.

A common problem in pile cropping is when fracturing or spalling occurs beneath the surface of the concrete. This can be frustrating, time-consuming, and costly for construction teams to fix. By choosing the right pile cropper for the job, damage to piles can be avoided, saving time and money.

Advantages of Using a Hydraulic Pile Cropper

• Significantly faster than conventional methods, capable of cropping up to 100 piles per day
• Compact and easy to transport
• Low cut-off level
• Easy to operate
• No noise or vibrations
• No cracks below the cut level when using reinforced de-bonding methods
• The reinforcement remains fully intact and undamaged
• Leaves a perfect horizontal concrete fracture at the pile cut-off level
• Easily adjustable
• Complies with health and safety guidelines for hand-arm vibration injuries