7.1 Piling Operations: Rigs, Working Platforms, Driven and Bored Piles

Why piling needs special attention

Piling rigs are tall, heavy and often top-heavy. They work on new, sometimes soft ground at the very start of a project, when access, drainage and site organisation are least developed. Typical serious events include:

• rigs overturning because a track sank into soft ground or ran off the platform edge
• workers struck by swinging piles, hammers or casings
• falls into open bores
• hydraulic hose failures
• contact with overhead or underground services
• damage to neighbouring buildings from vibration and ground movement

NADOPOD 2004 lists the collapse, overturning or failure of a load-bearing part of a piling frame as a dangerous occurrence (Second Schedule, Part I, item 11).

Piling methods in Malaysia

Ground and working platforms: preventing overturns

Under CDM 2024 regulation 21, any temporary support, which includes a granular piling platform that carries a rig, must be designed, installed and maintained to withstand foreseeable loads and used as designed. Rig loads are highest, and least even, when:

• lifting a pile or reinforcement cage
• extracting a casing
• travelling with the mast up
• slewing

The platform design must therefore start from the rig manufacturer's track pressure data for those cases.

DOSH's public safety guideline (section 19.6) says that before a pile driver is placed or advanced, the ground shall be inspected by a designated person and, where necessary for firm and level footing, timber shall be placed. After the rig is placed or moved, the footing must be inspected and corrected as needed to keep it stable.

Practical platform controls:

• a design by a competent engineer, matched to the rig's worst load cases, with the platform material, thickness and compaction specified and tested
• a platform certificate or handover record before the rig arrives, renewed after rain, excavation nearby or damage
• no unplanned excavations, trenches or soft spots beneath the platform, and backfilled pile holes or old trenches marked
• clear, marked platform edges, with the rig kept well back from them and from slopes and excavations
• drainage, so the platform does not soften in monsoon rain
• rig operation within the manufacturer's limits for slope and wind, checked with the rig's inclinometer and anemometer where fitted

Daily rig inspection

DOSH's public safety guideline (section 19.4) says all pile-driving equipment shall be inspected daily by a designated person before work starts, and every defect corrected before driving.

A daily checklist typically covers:

• Wire ropes and terminations: broken wires, kinks, crushing, corrosion, correct reeving and drum wraps, all judged against the manufacturer's discard criteria
• Mast, leaders and backstays: pins and retaining clips, welds, guides, hydraulic rams
• Hammer, helmet and dolly or cushion: wear, cracks, secure fixings
• Hydraulics: leaks, chafed hoses, whip checks (restraints) on hose couplings, guards
• Safety devices: limit switches, load and angle indicators, emergency stops, horn and lights, reversing alarm
• Operator: trained and authorised for the rig; logbook entries made

Where a crane is used for pitching, it must have a valid certificate of fitness and be operated by a competent crane operator to a lifting plan (Plant Requiring Certificate of Fitness Regulations 2024, regulation 15). See Chapter 8.

Handling and pitching piles

• Plan the lift. Use the designer's lifting points or a pick-up method that does not crack the pile. Make sure the crane or rig winch is rated for the pile's weight and the radius.
• Use taglines to control swinging piles, and keep everyone out of the swing path.
• Exclusion zones cover the drop zone of the hammer and pile, the slew radius of the counterweight, and the area where a pile could fall if it breaks or the sling fails. Only the banksman and essential crew enter, and only when the operator knows they are there.
• Never stand under a suspended pile or hammer. Never guide a pile by hand at its base while it is being lowered into the leaders.
• Stack piles on level bearers with chocks, no higher than the stack can stay stable, away from traffic routes.
• Head trimming of piles uses breakers or cutters that produce noise, vibration, dust and flying fragments. Use the hierarchy: hydraulic crushers, water suppression and PPE (Chapter 10).

Bored piles and support fluids

• Open bores are a fall and drowning trap, especially when filled with slurry. Cover or guard every unattended bore at once with a secured, load-rated cover or full barriers. Never leave a casing flush with the ground unguarded. CDM regulation 19(3) requires floor-level openings that could cause falls to be guarded, and the same principle applies to bores.
• Support fluid (bentonite or polymer): manage mixing tanks, pumps and spills. Slurry makes platforms slippery and weak. Guard ponds and tanks against falls, and provide washing facilities because the fluids irritate the skin.
• Reinforcement cages are long, heavy and flexible. Use a lifting plan with two-point lifts and spreader beams as designed, with taglines, and keep people clear when a cage is lowered or spliced over the bore.
• Tremie concreting: pipe joints, hopper platforms with edge protection, and safe positioning of concrete trucks near the bore.
• Casing extraction produces very high loads. Follow the rig's rated extraction capacity and keep exclusion zones.

Pile testing

DOSH's public safety guideline (section 19.5) says reasonably practicable measures should warn people not to approach within 50 m of a pile under test. This guards against a kentledge collapse or the failure of a jack or reaction frame during static load testing. Kentledge stacks must be designed, built on firm ground and inspected.

Noise, vibration and neighbours

• Built-up areas: DOSH's guideline (section 19.2) says piling machinery that produces excessive vibration, noise, smoke or other pollutants should not be used there. Bored or jack-in methods are often chosen instead of driven piles.
• Noise at source: for example a non-metallic dolly between the hammer and the helmet, or an acoustic enclosure around the hammer and the full length of the pile; better exhaust silencers or acoustic canopies on engines (section 19.7 and 19.8).
• Workers' exposure: follow the Noise Exposure Regulations 2019. Noise risk assessment, hearing protection zones, approved hearing protectors and audiometric testing apply where exposure is excessive (Section 10.1).
• Adjoining structures: where their stability is in question, support them by underpinning, sheet piling, shoring or bracing to a Professional Engineer's design (section 19.3), and monitor vibration and movement.

Services

• Before drilling or driving, locate and protect underground services (CDM regulation 27(4)). Check the mast height against overhead lines when travelling and erecting, and set up goalposts and barriers where needed (Section 3.1).
• Bored piles near gas or water mains need trial holes and the asset owner's agreement.

Scenario: rig overturn averted

A 70-tonne bored piling rig is due to move to a new row of piles near a recently backfilled drain. Overnight rain has softened the platform edge. The SSS:

1. Stops the move and asks the designated person and the temporary works engineer to inspect the platform (DOSH 19.6).
2. Finds the drain backfill was not compacted under the platform design, and arranges excavation, recompaction and testing of that area, with steel plates used as the design requires.
3. Has the rig's route re-marked well away from the platform edge, and briefs the banksman on the move.
4. Records the near miss, and adds "platform inspection after rain" and "no excavation under the platform without engineer approval" to the piling permit and the site rules.