This class covers ancillary works required for piling operations other than the piles themselves (Class P). These items are necessary for the execution, support, or completion of piling works but are not measured as part of the pile length.
1. Scope
Class Q includes:
- Guide walls.
- Pile caps and pile cut-offs (if not covered under Class P).
- Diaphragm walls used in conjunction with piles.
- Ground treatment and grouting connected with piling.
- Temporary and permanent casings beyond cut-off level.
- Bentonite slurry or drilling fluid systems (supply, circulation, disposal).
- Working platforms, pile mats, and access for piling rigs.
2. Subdivision of Items
The work is subdivided into:
- Q.1: Guide walls – temporary or permanent, usually for diaphragm walls or secant piles.
- Q.2: Pile caps – including excavation, formwork, reinforcement, and concrete.
- Q.3: Casings and linings – temporary steel casings, permanent liners, inserted and removed or left in position.
- Q.4: Ground treatment – grouting, bentonite, polymers, or cement stabilization.
- Q.5: Working platforms/pile mats – providing stable ground for piling rigs.
- Q.6: Ancillary structures – pile collars, cut-off walls, guide beams, tremie pipes.
3. Method of Measurement
- Guide walls – measured in cubic metres (m³) for concrete or in square metres (m²) for formwork.
- Pile caps – measured separately for excavation, reinforcement (tonnes), and concrete (m³).
- Casings – measured per metre (m) of insertion length.
- Ground treatment – measured in cubic metres (m³) or number (No.) depending on method.
- Working platforms/pile mats – measured in square metres (m²).
4. Item Coverage
Unless otherwise stated, items shall cover:
- Setting out and alignment.
- Excavation, support, backfilling, and disposal of surplus material.
- Supply and installation of temporary or permanent casings.
- Handling and circulation of bentonite/slurry including disposal.
- Provision of pile working platforms and access ramps.
- Cutting down piles and constructing pile collars/pile caps.
5. Notes for BOQ Preparation
- Always state whether casings are temporary (to be removed) or permanent (left in place).
- For pile caps, specify dimensions, depth, and reinforcement type.
- Guide walls should clearly mention thickness and height.
- Slurry requirements (bentonite or polymer) should be separately itemized.
- Working platform thickness and material (granular, crushed stone, etc.) must be described.
- Ground treatment methods (cement grout, chemical, jet grouting) should be specified.
6. Example BOQ Items
- Q.1.1: Reinforced concrete guide walls 600 mm thick, 2.0 m deep, for diaphragm wall piling, measured per m³.
- Q.2.1: RCC pile cap 2.5 × 2.5 × 1.2 m, including formwork and reinforcement, measured per item.
- Q.3.1: Steel casing 1,000 mm dia, inserted and removed, measured per metre.
- Q.3.2: Permanent steel liner 800 mm dia, left in place, measured per metre.
- Q.4.1: Cement grout ground treatment beneath pile cap, measured per m³.
- Q.5.1: Granular working platform for piling rig, 500 mm thick, measured per m².
