GROUND INVESTIGATION

Part of our Data Acquisition Solution

Today’s engineers face a range of challenges when it comes to sustainable, robust and affordable design. Projects are often developed where ground conditions are unknown or undocumented, and the more extreme weather conditions due to climate change are putting assets and structures to the test. A relatively small amount of investment in ground investigation at the outset of a project can provide large savings in the long term.

The protection of the environment has become increasingly important with the development of brownfield sites, changes in legislation and increased public awareness around environmental issues. Ground investigation provides a means of establishing levels and extent of contamination in the ground. It enables risk assessment to be undertaken with regards to risk to human health and the environment. 

Our ground investigation team provides integrated site investigation services, including all aspects of drilling, in-situ testing, reporting, and laboratory testing, utilising our sister companies UKAS-accredited laboratories.

We are an experienced team of engineering geologists and geo-environmental engineers, operating across all sectors across the UK which has given us a great depth of knowledge of client needs, UK ground conditions and how to deliver complex GI’s, often in challenging environments.

With the capabilities to resource and support projects nationwide, we are problem-solvers. Our goal is to collaborate with our clientele and support projects at the early contractor involvement stage, with a best-for-project approach.

A dark, muddy/gravelly slope, with cabins and diggers set out on the slope, with trees, the blue sky and clouds in the background.

Slope & Difficult Access Ground Investigation

Central Alliance have developed a range of slope and difficult access drilling rigs, capable of accessing restricted sites, to deliver high-quality geotechnical data required by design engineers. Drawing on our experience with current drilling technologies and projects in difficult-to-access locations, we have designed rigs that are ‘true geotechnical investigation’ rigs.

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Our Fleet

We own and operate our own fleet of drilling rigs, which are continuously updated with a significant capex budget, to meet modern standards. Our experienced team of drilling crews work across all sectors to get the best out of every investigation.

GT150K Slope Climbing Rig
GT150K Slope Climbing Rig
A window sampling rig set out on a railway line, with two Central Alliance drillers dressed in hi-vis clothing, operating the rig, with greenery and a grey sky in the background.
Premier 110
A window sampling rig set out on grassy land which is down hill of slope which sits in front of a railway line, with a Central Alliance driller dressed in hi-vis clothing operating the rig, with greenery and a blue sky in the background.
Tracked Dynamic Sampling Rig
A Dando 4000 Cable Percussion rig set out in a yellow flowery field, with green bushes and a blue sky in the background.
Dando 4000
A Cable Percussion rig set out on dry, frosty grassy land at Fowlea Brook, with buildings and a grey sky in the background.
Dando 2000
A Fraste SLG rig set out on a railway line, next to Fowey Estuary, with a Central Alliance driller operating the rig. There are trees, a grassy hill and boats in the estuary in the background.
Fraste SLG
A Dando Terrier rig set out on a pontoon, with a Central Alliance worker stood to the left of the rig, dressed in hi-vis clothing. The pontoon holding the rig is set out on a canal in Leeds, and there is greenery and the sky in the background.
Dando Terrier
A Comacchio Geo 300 rig set out on hard ground, with heras fencing around the rig and two Central Alliance drillers dressed in hi-vis clothing operating the rig. There is also buildings, the sky and bare trees in the background.
Comacchio Geo 300
Fraste PLG rig set out on dry, grassy land, with two Central Alliance workers operating the rig, dressed in hi-vis clothing on site at Connahs Quay. There are various bits of tools on the grassy land, and there is a blue sky and buildings in the background.
Fraste PLG
A Massenza Mi5 rig set out in front of a coal stocks site, with two Central Alliance workers dressed in hi-vis operating the rig. There is a van with a unit on the back to the left of the rig, and there is a cloudy sky in the background.
Massenza Mi5
A Comacchio Geo 205 rig set out in a bright green, long grassy field, with trees and the blue sky in the background.
Comacchio Geo 205
Fraste ML
Fraste ML
A Central Alliance slope climbing drilling rig set out on a grassy slope, with the mast at a 45 º angle.
Massenza MIP3
GT300 Slope Climbing Rig & Mule
GT300 Slope Climbing Rig & Mule
Hagglund BV206
Hagglund BV206

Conventional Drilling Methods

Rotary Drilling

A Central Alliance bright orange, Fraste drilling rig set out in a field, with heras fencing set out around the rig, with the sea, clear blue sky and trees in the background, on site at Parsons Tunnel in Teignmouth.

Boreholes formed by rotary drilling equipment are normally used when rock or hard ground is anticipated, using rotary techniques to drill through the rock or solid geology. The two types of rotary boreholes that are frequently used on ground investigation projects are rotary open holes and rotary cored holes.

 

Rotary open holes are drilled when rapid progress is required on projects, such as mining investigations, when the structural details of the rock are not necessarily important. This is because the main focus is on the presence of voids that could indicate shallow mine workings. Rotary cored holes are drilled when structural details of the underlying rock are required. These are generally used in applications such as when a proposed development has heavy loadings, requires deep foundations, or when the site is underlain by shallow bedrock.

 

We own and operate an extensive fleet of rotary rigs, including three Fraste PLGs, a Fraste ML, a Massenza Mi5, two Massenza MiP3s, a Comacchio 205, a Comacchio 300, a Dando Terrier, and a Fraste SLG. The techniques used include conventional coring, Geobore-S wireline, open holing, down-the-hole hammer, and hollow stem auger with wireline sampling. A majority of our rigs are multi-purpose and capable of dynamic sampling through superficial deposits and standard penetration tests (SPT).

Cable Percussion

A Cable Percussion rig set out on dry, frosty grassy land at Fowlea Brook, with buildings and a grey sky in the background.

Cable percussion (CP) boring is one of the most reliable, well-tested, and robust drilling techniques in the UK. It is capable of boring through the wide range of superficial deposits that we encounter in the UK. A cutting tool (shell, clay cutter, etc.) is driven into the ground using percussive force. Casing of a variety of diameters can be installed to prevent the hole from collapsing, enabling good progress to be made. CP boring is incredibly versatile and can handle consolidated and unconsolidated soils. We currently own several CP rigs with varying capability of drilling depths up to around 100 m.

Dynamic Sampling & Dynamic Probing

A window sampling rig set out on grassy land which is down hill of slope which sits in front of a railway line, with a Central Alliance driller dressed in hi-vis clothing operating the rig, with greenery and a blue sky in the background.

Dynamic sampling rigs are smaller rigs, capable of sampling through superficial deposits. They’re a very useful tool for quick, shallow, and unconsolidated ground investigations. Our conventional rigs are rubber tracked, with low ground pressure self-propelled units, so they can access any site where shallow soft soil sampling is required. Our fleet of rigs also includes several modular rigs for restricted access and slope working. They are ideal for a ground investigation that requires chemical sampling, installing ground gas and groundwater monitoring wells for subsequent environmental monitoring, and in-situ geotechnical testing of the shallow underlying soils.

 

A drop hammer drives the sampling tubes into the ground, and standard penetration tests (SPT) can be undertaken with all rigs, along with undisturbed sampling. Dynamic sampling rigs are much faster to set up over a position than the larger rigs. They can access more positions per day than conventional cable percussion drilling. Our fleet includes Premier 110s, Tecops, and Dando Terriers.

 

 
Cone Penetration Testing

We own and operate a cone penetration testing (CPT) crawler rig which is capable of tracking through most terrains. Our CPT rig offers a 200 kN push from a stable platform and is able to average over 100m of data acquisition per day.

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Further GI Capabilities
Central Alliance worker dressed in hi-vis clothing, operating CSW equipment on a railway line at a site in Scotland, with greenery and the sky in the background.

Continuous Surface Wave Testing

The seismic energy source of the continuous surface wave equipment, with an operating range of 5-100 Hz, produces surface or ‘Rayleigh’ waves that propagate across the ground surface. These are detected by a system of geophones and analysed by the software. The laptop-based software uses the data to provide a stiffness versus depth profile. Office-based post-processing can provide shear wave velocity profiles and subsequently, mechanical properties of the ground, such as shear modulus and elastic (Young’s) modulus.

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Monitoring

Our team can provide the most comprehensive range of supplier-agnostic instrumentation and monitoring solutions, including geotechnical monitoring services. Our expert engineers routinely carry out installation of automated monitoring and undertake manual monitoring on behalf of a wide range of clients.

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Central Alliance worker dressed in hi-vis clothing, operating manual monitoring equipment on a site on the A57, Snake Pass, stood on grassy land, with hills and the sky in the background.
Machine excavated trial pitting on Quanterness, Orkney Islands, Scotland.

Trial Pitting

Machine excavated trial pits can often provide the most practical and economical method of site investigation and assessment. Trial pits allow observations on the mass characteristics of soil. It is often used to obtain larger soil samples for laboratory testing, to facilitate in-situ testing and engineering logs of shallow strata. This can be important when dealing with variable ground conditions.

Laboratory Testing

Our in-group laboratories can undertake a wide range of laboratory testing services with a strong emphasis on quality. We provide the full range of soil and materials testing via our laboratories across the UK. The laboratories can carry out the full suite of tests and classification tests, as specified by British and ISO standards (BS, BS EN, ISO). All tests are performed in strict accordance with set methodologies and guidelines. The laboratories also carry out International Society for Rock Mechanics rock tests, and are able to test in accordance with less commonly requested ASTM International test methods. We can also work with clients to create bespoke-site or project-specific testing solutions.

Laboratory data deliverables includes digital in both AGS and PDF formats.

Our sister company CJ Associates offer a range of concrete testing options. We can test the compressive strength and density of concrete cubes. We can also test the unconfined compressive strength of concrete cores (non-UKAS accredited). For help aggregates, we also provide aggregate grading. We can also provide a full range of all geotechnical and environmental testing laboratories in RSK.

Engineer sampling soil and water for laboratory testing. Geotechnical and Chemical testing.
Two engineers undetaking in-situ testing using a TRL DCP probe.

In-Situ Testing

In-situ testing is an essential part of geotechnical engineering. Measurement of parameters in-situ can have significant advantages over laboratory testing. Our engineers, technicians and drillers are skilled at using the standard in-situ testing methods, including the standard penetration test (SPT), the cone penetration test (CPT), dynamic probing, Mackintosh and TRL probes, california bearing ratio (CBR), plate bearing test, in-situ density tests, field shear vane, permeability testing, soakaway testing, infiltration testing and continuous surface wave testing.

Backed by its extensive history in the industry, our sister company CJ Associates has built a dedicated team of expert in-situ testing technicians. Our team provides an integrated service in wider site investigations to support projects by acquiring high-quality, on-site data. These services are in addition to more standard tests undertaken in exploratory holes, such as standard penetration testing, shear vanes and dynamic probing. We also acquire and test samples of fresh concrete, in addition to concrete slumps or making concrete cubes for compressive strength tests. We can provide further concrete and tarmac related services, including diamond coring with either road towable trailer mounted rigs or hand-held rig, tarmac – air voids content (non-nuclear gauge), macrotexture, texture depth and rolling-straight edge.

For any requirement to take a reading of in-situ resistance to a depth of 850 mm (or deeper), we can provide the transport research laboratory, dynamic cone penetrometer, which is a non-UKAS accredited test. We can also provide continuous surface wave testing for ground stiffness profiling along with cone penetration testing.

Measure Whilst Drilling

To realise the full value of ground investigations, measure whilst drilling (MWD) systems, OR drilling parameters recording (DPR) allows the capture of a vast amount of data to provide insights that may otherwise be missed using conventional drilling and logging techniques. Depth, penetration rate, rotation speed, rotation torque, head pressure, holdback pressure, pressure and flow rate of the injection fluid, inclination and reflected vibration can all be recorded.

Measure whilst drilling equipment set out on the grass on site. The equipment consists of a standing screen and an attachment that is added onto the rig.
A map with a piece of paper placed over the centre, and a hand in the bottom right corner writing something with a pen on the page.

Factual & Interpretive Reporting

Factual reports are written by our highly qualified and experienced team of geotechnical and geo-environmental engineers, and cover every aspect of the site investigation, including:

  • Purpose and scope of the investigation
  • Accounts of all field and laboratory work
  • Exploratory hole records (trial pits, window sample holes and boreholes), including grid coordinates and levels
  • Any in-situ test results
  • Any laboratory test results
  • Any instrumentation and monitoring results
  • Site plans, including locations of any exploratory holes
  • The provision of data in various formats.

Our geotechnical engineers have extensive experience in the logging of soil and rock to BS 5930-2015, BS EN ISO 14688-1 2002 and BS EN ISO 14688-2 2002, along with relevant CIRIA guidance.

Technical advice can be provided from our team who are highly qualified experts in a wide range of fields, including engineering geology and foundation design, to offer solutions to geotechnical problems connected with:
 
  • Adequate load bearing for shallow and deep foundations
  • Settlement estimations
  • Slope stability/instability
  • Causes of failure
  • Ground improvement solutions
  • Interpretive reporting
Our Services