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Coinford will be involved in piling operations, either as Principal Contractor appointing piling contractors, Principal Contractor managing piling contractors appointed by the client, or as subcontractor attending the piling operations. It is generally recognised that most of the piling or ground stabilisation on our projects is undertaken on behalf of the client. We do however offer our services as pilling attendance on site, for removal and clearing of resulted spoil from the pilling process. Piling is acknowledged as a high risk activity, one which if not planned correctly can bring significant consequences and potentially loss of human life.
There are several types of piling available:
CFA - Continuous Flight Auger;
Rotary Bored Auger;
Driven Concrete Piles;
Driven Shell Piling;
Contiguous Piling;
Vibro Compacted Stone Columns; and
Driven Steel Sheet Piles.
If any of these types of piling are specified by the Engineer responsible for the Foundation design, certain safe systems of work will need to be implemented prior to piling work commencing. They can be summarised as follows:
Full survey for existing services or underground obstructions or possible unexploded ordnance;
A designed and adequately filled and compacted level piling matt;
Soil reports for any contaminated spoil which may be hazardous and may require a change of pile design (driven piling will not create spoil for removal);
Any overhead high voltage cables;
Adequate access for heavy plant and machinery and concrete supply lorries on designed haul roads;
Pedestrian segregation and possible exclusion zones;
Additional welfare facilities must be provided if the ground is contaminated;
Wash out facilities for concrete lorries and concrete pump pipe lines protection of water courses;
Adequate provision must be made to protect freshly completed piles with projecting reinforcement; this will normally take the form of mushroom caps being fitted by the piling or groundwork’s contractor.
Pre start meeting with all parties, dealing with any environmental issues such as noise, dust, vibration and adequate arrangements are agreed. The project management team is to ensure that a method statement is received and reviewed at least two weeks before work commences on site. The Operations Director is responsible for monitoring compliance with this procedure.
Piling works close to an operational railway will require careful planning and liaison with Rail Company, the works to be undertaken will have to comply with their Contract Conditions regarding safety and the line standards.
London Underground will also have specified requirements for piling works and crane operations which interface with train movements.
It is important to differentiate between cranes and piling rigs. Piling rigs are either purpose made machines or cranes specially adapted for piling by fitting masts / leaders or power boring equipment.
Cranes used for servicing piling rigs for placing pile liners or reinforcement cages must be used in accordance with relevant standard and with the Lifting Operations and Lifting Equipment Regulations. Piling rigs are classed as lifting equipment and therefore require a thorough examination after assembly and before being put into service at a new site or in a new location and then at 12 monthly intervals.
Lifting accessories such as chains, ropes, shackles, lifting bridles, require 6 monthly examinations as normal.
It is imperative that an adequately designed and compacted piling matt is provided and maintained throughout the programmed period for piling works. Piling rigs or cranes which do not operate on a firm level base are easily overturned by lifting augers full of spoil or cranes servicing piling rigs.
A proforma for a working platform certificate can be found on the following page. This certificate must be given to the piling contractor upon completion of the piling mat installation.
The design and review of the piling mat design will be held onsite in the Temporary works file.
If soil samples tested before work commences reveal contaminated soil is evident, it would be a duty of the Principal Designer to ensure the designer has the necessary information to change the pile design to prevent disposal of contaminated materials driving Pre-cast piles, or Vibro concrete piles may be an option.
If however it is not reasonably practicable to re-design then control measures such as personal protective equipment or respiratory protective equipment may be required a detailed risk assessment will need to be carried out. Also the services of an occupational health nurse on site or on a visiting capacity will be required to carry out health surveillance.
As part of the design process the type of method to be used for pile breakdown should be incorporated in the H&S Information Pack, there are systems designed to prevent exposure to Vibration White Finger (VWF) and Work Related Upper Limb Disorders (WRULD). Pile breakdown can be achieved mechanically by the Elliot method (or similar) using pipe lagging foam on the pile rebar cage prior to concreting. A hydraulic splitter is inserted into a pre drilled hole, and then the redundant pile is lifted off with a crane. A small amount of trimming by hand may be required.
Another method is the hydraulic pile breaker mounted on a hydraulic excavator which sits over the pile at the required level and hydraulic rams break through the concrete. Some minor trimming by air tools may be required.
The use of handheld breakers must be strictly limited for the breaking and cleaning of pile caps, and only used other than when access for the mechanical alternatives is not practicable. All trigger times must be recorded and logged on HAV registers to ensure operatives exposure to vibration is not exceeded.
Sites situated close to rivers or docks were possible targets for heavy bombardment during the Second World War. Before piling commences it again would be incumbent on the planning supervisor and management team to make reasonable enquiries as to the possibility that UXB’s may be present. Where a high probability of UXB’s being found is identified then reasonable steps must be taken to identify the exact location (e.g. bomb probing) must be considered.
Following the completion of concrete placement the pile bore openings will need to be backfilled to prevent voids in the work area and any projecting reinforcement protected with hi visibility mushroom heads. If any pile bores are left without being concreted overnight the lining tube must be securely covered and access protected by fencing.
All crane drivers and piling rig operators will hold CPCS construction plant certification cards and Piling Operatives CSCS cards.
