Drilling Services

Dunelm offers a comprehensive range of site investigation and drilling services using our experienced and qualified in-house personnel. Site investigation and drilling services that are available include the following:

• Contract Management
• Cable percussion drilling
• Mini percussive drilling, window sampling and dynamic probing
• Window sampling using hand held equipment
• Concrete coring
• Rotary drilling (coring and open-hole)
• Trial pitting
• In-situ testing
• Hand excavation to locate building foundations
• Post site works monitoring and sampling

 

Contract Management

Dunelm are able to supply a rig and crew for drilling anywhere in the country. But Dunelm doesn’t just supply drilling rigs – we have a team who are experienced in managing large contracts that often extend over many weeks.

Many of our projects have involved drilling boreholes over water, in locations with difficult access such as in car parks and inside operational buildings, and on hazardous sites such as active chemical plants and petrol filling stations.

In addition Dunelm have extensive experience of carrying out drilling operations on sites such as schools, where many different surfaces need to be protected and reinstated to a very high standard on completion (eg. grassed playing fields, tarmac car parks and block paved areas).

All ancillary aspects of the site investigation such as site welfare, fencing, security, traffic management and survey work can be arranged if required, as can the removal of spoil to comply with waste management regulations, including registering the site as a hazardous waste producer if necessary. Dunelm can also arrange for a Ground Radar survey to be carried out prior to work commencing in order to minimise the risk of damaging buried services such as pipes and cables.

Dunelm have wide experience of acting as Principal Contractor in accordance with the Construction (Design and Management) Regulations 2007, working closely with the Designer and CDM Co-ordinator to ensure health and safety is managed effectively. Site-specific risk assessments are carried out by an IOSH-qualified project manager for all investigation activities and appropriate control measures implemented.

Each contract is assigned a project manager who will have extensive experience of co-ordinating operations, managing health and safety, and communicating with clients, site operators and other interested parties. The project manager also provides technical oversight of the works and is responsible for ensuring that information is passed to the client in a timely fashion.

Each contract would normally be supervised full-time by an experienced geoenvironmental engineer who is responsible for day to day management of the works and for producing records (logs) of the soil and rock strata together with photographs and other information required.

Dunelm recognise that these logs are one of the most vital parts of the site investigation and therefore all Dunelm engineers and drillers are thoroughly trained and assessed continuously in producing logs to the current British and European Standards (BS5930, EN ISO 14688 and 14689). All logs are carefully checked by senior staff before being issued.

The engineer is also responsible for ensuring that all samples are despatched to the appropriate laboratory so that testing can be undertaken.

All our drillers have considerable experience of drilling in different ground conditions and all have obtained (or are presently undertaking) the NVQ in Land Drilling. Drilling operations are overseen by a Drilling Manager who visits sites continuously to ensure that the required standards are being maintained.

More details about the site investigation and drilling techniques and the rigs we use can be found below.

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Cable Percussion Drilling

Cable percussion drilling is a tried and tested method of site investigation. The drilling technique allows the installation of casing inside the borehole to prevent loose soils collapsing into the hole, allowing the borehole to be advanced to considerable depths while maintaining good progress.

‘Clean’ drilling techniques can be utilised with the provision of different sized casing to prevent contamination in the near surface strata from affecting deeper strata. This is especially important on sites with high concentrations of mobile contaminants.

In-situ testing can be undertaken in the borehole including Standard Penetration Testing (SPT), borehole vane testing & permeability testing. 

Disturbed samples are taken from the borehole by the drillers for logging by an experienced geoenvironmental engineer. Undisturbed tube samples are also recovered for laboratory testing.  On completion, gas and groundwater monitoring pipes and geotechnical monitoring equipment can be installed in the borehole to allow later measurements by our dedicated technician.

Dunelm have four cable percussion rigs available, as well as access to specialist rigs which are suited to restricted access sites. The rig is towed into position using a Land Rover, meaning that these rigs can be used in most locations where there is sufficient space; a considerable working area is required however. The rigs are fitted with lifting points enabling them to be moved into position by a crane on difficult sites or onto an overwater drilling platform.

Boreholes can be drilled at a variety of diameters including 150mm, 200mm and 300mm. Larger size casing can be obtained when required. Brief details of our rigs are shown below.

 

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Mini Percussive Drilling, Window Sampling and Dynamic Probing

The mini percussive rig (mini rig) is a compact self-contained rig which can be maneuvered under its own power into locations with difficult access.  The rig is transported to site in a panel van together with all ancillary equipment, allowing rapid and inexpensive mobilisation to any location in the country.

The rig can also be used on gently sloping sites which may not be accessible by the cable percussion rig. The mini rig is mounted on tracks allowing access over soft ground surfaces, and can fit through a standard doorway allowing drilling to be undertaken inside buildings. Drilling and sampling to depths of 5 to 10m is achievable depending on ground conditions.

Disturbed samples are taken from the borehole and logged by an experienced geoenvironmental engineer. Standard Penetration Testing (SPT) and borehole permeability testing can be undertaken within the mini boreholes. On completion, gas and groundwater monitoring pipes are often installed in the borehole to allow later measurements by our dedicated technician.

Dunelm also have dynamic probing equipment (DPSH ‘super-heavy’ specification) which can be fitted rapidly in place of the sampling tools. This allows dynamic probing to be alternated with fully sampled boreholes, providing a versatile site investigation method.

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Concrete Coring

The mini rig can also be equipped with a concrete corer unit, allowing samples of surface concrete 150mm in diameter and up to 300mm thick to be recovered for testing.

This method also allows the surface to be reinstated to a neat finish and is often used to enable long-term monitoring points to be installed in heavily trafficked locations such as petrol filling station forecourts.

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Window Sampling using Hand Held Equipment

On some sites, access is too restricted even for the mini rig. In this situation Dunelm can provide a hand-held window sampling system that enables samples to be recovered using the same tubes as the mini rig.

This system comprises a hand-held hydraulic breaker with a separate power pack and has been used successfully on slopes of up to 25 degrees. On steep slopes a small horizontal platform is excavated first using hand tools, and fall arrest equipment can be provided if required to ensure the safety of the crew. Diesel-engined hydraulic packs can be supplied for sites where the normal petrol-engined plant is not safe.

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Rotary Drilling

Rotary drilling techniques are utilised where drilling into bedrock is required to check for shallow mine workings or to determine rock quality.  All our drilling rigs can undertake rotary coring to recover rock core samples at various diameters. The cores are then logged by experienced geoenvironmental engineers in accordance with the relevant British and European standards.

Alternatively the borehole can be drilled using rotary open hole methods in which samples are not recovered; rock cuttings are returned to the surface during the drilling and this allows a rapid examination of the strata. This method is often appropriate to locate shallow coal seams or mine workings and allows a number of boreholes to be completed in a short space of time.

Continuous monitoring of gases such as carbon monoxide, methane and carbon dioxide can be carried out while drilling through old mine workings.

All of our rotary rigs are able to carry out Standard Penetration Testing (SPT) in soil or rock. On completion, gas and groundwater monitoring pipes are often installed in the borehole to allow later measurements by our dedicated technician. Our crews have experience of drilling and sealing off boreholes through rocks containing artesian groundwater conditions.

In some cases it is possible to combine site investigation drilling with the installation of ground loops for heating purposes, achieving overall cost savings for the project; our sister company Dunelm Well Drilling can provide further information on this aspect.

Dunelm have a variety of rotary drilling rigs available to suit all types of projects. Each rig is supplied with a separate compressor unit, together with water bowser if required and all other equipment needed. The rigs are mounted on wheels or tracks to enable access over different types of terrain.

Ground mats can be supplied for use on soft surfaces such as grassed playing fields where the surface needs to be preserved.
Simultaneous drilling and casing using a Symmetrix system can be undertaken to enable drilling through unstable ground and a variety of different flushing systems are available as appropriate to the ground conditions.

Brief details of our rotary rigs are shown below.

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Trial Pitting

Dunelm can also undertake a trial pitting investigation, with full-time supervision by an experienced geoenvironmental engineer. The method involves the mobilisation to site of a suitable tracked or wheeled excavator. This machine is then used to excavate through the strata while the Dunelm engineer records the nature and depth of the soils and also recovers samples for laboratory testing. On completion the excavated soils are replaced in the same order to leave a safe ground surface.

Trial pits are a rapid and cost effective method of assessing the shallow ground conditions at a site, since a number of trial pits can be completed in a single day. Trial pits can provide an assessment of obstructions in the near surface ground, particularly on previously developed sites.

It is also possible to excavate long trial trenches in order to determine the location of buried features such as the edge of a quarry.

In-situ testing

Dunelm can also carry out in-situ plate load and CBR testing using a wheeled excavator; these tests are normally carried out during the trial pitting investigation. Other forms of in-situ testing such as cone penetrometer testing, geophysical surveys etc can also be undertaken as part of a wider site investigation.

Trial pits also enable soakaway tests to be carried out in order to evaluate a site’s drainage options. Dunelm can supply the complete set of equipment for this test including water bowser, pump etc, and can supervise the test to ensure that it complies with the relevant standard.

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Hand excavation to locate building foundations

Dunelm also have extensive experience of excavating by hand adjacent to existing buildings in order to provide information on the foundations. It is often necessary to commence these excavations using hydraulic power tools in order to penetrate concrete or tarmac. Diesel-engined hydraulic packs can be supplied for sites where petrol-engined plant is not safe.

Dunelm crews are able to provide a full reinstatement service of the ground surface on completion, even where this comprises block paving or tarmac.

Dunelm have also carried out larger scale excavations inside buildings to investigate column bases using micro-diggers and hydraulic tools. Re-bar surveys can also be arranged to provide further information on the structure of the building.

 

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Post site works monitoring and sampling

Once the drilling is complete, Dunelm provide a dedicated technician who carries out groundwater and gas monitoring on completion of the drilling works. This ensures that consistently high quality data are provided for long term measurements. A wide range of gases can be recorded as well as measurements of free phase oil on contaminated sites. Groundwater and gas samples can also be recovered, in accordance with the latest guidance, for laboratory analysis.

Permeability testing can also be undertaken in groundwater standpipes using either ‘slug’ test electronic transducer equipment or traditional methods.