Structural Soils has an extensive in-house fleet of drilling rigs, as well as direct access to additional drilling rigs through our sister companies

Our lead drillers and assistants hold industry-recognised qualifications, including the NVQ2 and BDA accreditation.  Our drilling teams are highly experienced with all types of geotechnical and geoenvironmental ground investigation and they understand the importance of quality and safety.

Our comprehensive fleet includes rotary, sonic, cable percussion and window sampling rigs suitable for most application, including difficult access and restricted headroom drilling.

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Rotary and sonic-rotary boreholes

Our rotary and dual sonic-rotary drilling rigs have the advantage of producing a continuous sample of the underlying soil and rock. As well as standard ground investigations, our rigs are capable of investigating mineral workings, drilling inclined (angled) boreholes and working in restricted access areas. We have a low ground pressure rotary rig and support dumper for access across soft ground.

We have various sizes of rotary rigs, which use a mixture of dynamic sampling to recover Made Ground and superficial deposits, and rotary coring to recover hard clays and rock. Our dual purpose sonic-rotary drilling rigs have the added capability of sonic drilling through Made Ground and superficial deposits that would be difficult for either dynamic sampling or cable percussion techniques. Having both rotary and sonic capability in one rig saves on mobilisation fees and saves time switching between traditional purely rotary and purely sonic rigs.

All our rotary rigs have open hole capabilities and have onboard wireline winches allowing for simultaneous casing while drilling (‘wireline’ or Geobore-S), which speeds up production and keeps boreholes stable.

All three techniques (dynamic sampling, rotary coring and sonic drilling) provide the engineer with continuous samples in a clear plastic tube for subsequent photographing, logging and sub-sampling. SSL have a range of drilling equipment to provide options for rock core diameters from 59 mm to 107 mm. In addition, in-situ testing (e.g., SPT, permeability, packer) and Class 1 samples can be obtained at any frequency or depth. Rotary boreholes are suitable for all types of installations.

Depending on conditions, our drilling rigs are capable of reaching depths of approximately 200m below ground level.

A selection of the drilling rigs available:

  • Dual rotary-sonic Comacchio Geo305 and Geo600-series – medium and large sized rigs capable of dynamic sampling, rotary coring and sonic drilling
  • Comacchio Geo205 and Massenza Mi3 – small track-mounted multipurpose drilling rigs capable of carrying out a variety of drilling techniques, making them a compact ground investigation rigs. Our Geo205 also cuts down for sites with restricted headroom.
  • Comacchio MC405 and Geo300 series – medium track-mounted rotary units capable of accessing locations on less compact ground
  • Comacchio MC450p and Geo600 series – Large rotary drilling rigs capable of the deepest boreholes
  • Low ground pressure rotary rig and support dumper

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Cable percussive boreholes

Cable percussive (‘CP’) boreholes are a cost effective method for intrusive investigations to rockhead.

A borehole is drilled by using tools to remove soils from the ground, and the borehole is held open with temporary casing.  Some of the arisings are bagged and retained as samples.  Class 1 samples and SPT tests are commonly taken at regular intervals throughout the borehole, and other in-situ testing is common such as permeability testing and borehole vane tests.

The rig is capable of boring through most Made Ground, superficial deposits (e.g., clays, sands, gravels) and weathered bedrock until the rock becomes too hard for the tools to excavate.  Maximum depths depend on the ground conditions, but they can be up to 100m deep, although usually CP boreholes are less than 50m deep.  CP boreholes are often used for drilling to the bedrock and then a rotary drilling rig is used to deepen the borehole.

For more information such as rig types, dimensions and working areas, see our Rig Specification Sheet – Cable Percussion Rig.

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Window and dynamic sampling

Window sampling uses either track-mounted or hand-held hydraulic percussive sampler rigs and involves driving cylindrical steel tubes into the ground using a percussive hammer. Window sampling is particularly suited to shallow intrusive investigations, restricted access sites, contamination investigations, and sites where disturbance must be kept to a minimum.

Samples are retrieved in seamless clear plastic tubes for photographing, logging and sub-sampling photographing by our suitably qualified engineers. All our window and dynamic sampling rigs have the capability to undertake dynamic probing. The track-mounted equipment is also capable of carrying out standard penetration testing and dynamic probing. As with rotary and cable percussive boreholes, these boreholes can be installed with instrumentation.

Rigs available include

  • Dando Terrier and Archway Competitor Dart – small track-mounted soil-sampling rigs designed to carry out rapid, relatively shallow ground investigations for geotechnical and geoenvironmental assessment
  • Electric Window Sample Rig – this is used inside buildings or in confined areas where diesel fumes from a regular WS rig would be hazardous.
  • Hand-held Window Sample Rig – this rig can be carried by the drillers so it is used for locations where no other drilling rig can access
  • ATV-mounted Window Sample Rig – mounted on a Supacat and ready to go without the need for unloading and loading at every borehole location, this drilling rig can travel across fields rapidly

For more information such as rig weights, dimensions and working areas, see our Rig Specification Sheet – Window Sample Rig.

Dynamic probing

Dynamic probing involves driving a steel cone vertically into the ground using a hammer and the operator recording the number of blows for each 100 mm of penetration. Several versions of the test methodology are available, the usual being ‘super heavy’.

The test provides a continuous profile of ground resistance with depth and is therefore able to locate boundaries between strata of differing density and driving resistance. The dynamic probing results may be used to establish the subsurface presence of obstructions such as old foundations or buried objects. Additionally, the results can be used to identify soft areas and voids or cavities within the soil, such as make-up of embankment fills, dissolution features in chalk or mine workings.

Our in-house resources are also capable of undertaking hand held TRL-DCP testing and Mackintosh probing. Both these techniques are ideal if shallow surface soils need to be investigated, particularly in areas of restricted or limited access.

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Concrete coring

Concrete coring is the process of drilling or cutting through concrete pavement, floors, walls and ceilings. The cores can then be photographed and described by our engineers and if required, laboratory testing undertaken on the recovered core. The information obtained on the concrete cores can be used to assess the suitability of existing slabs to support new structures such as a mezzanine floor.

Our teams have also carried out coring on masonry bridges and stone façades of historic houses to ascertain their composition and structure.

Where boreholes are located on a concrete slab, the concrete may be cored prior to commencement of drilling. This avoids the health and safety risks associated with breaking out using a hydraulic breaker, and the reinstatement is neater.

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Drilling is usually carried out with a combination of selected in-situ tests, sampling and installations, such as:

  • Standard penetration tests (SPT)
  • Borehole vane testing
  • Eurocode 7 compliant Class 1 samples (e.g., undisturbed sampling or piston sampling)
  • Variable head permeability testing
  • Packer testing or hydrotesting
  • Geophysical (downhole) logging
  • Groundwater and gas monitoring and sampling instrumentation
  • Earthworks monitoring installations such as extensometers and inclinometers

Expanding our capabilities further, are our wide range of sister companies and long-standing and trusted subcontractors, offering services such as dilatometer tests, pressure meter tests, pump tests and CPT tests.

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Structural Soils is part of the RSK group of companies

The RSK group is a leading integrated environmental, engineering and technical services business offering bespoke end-to-end solutions to a variety of sectors. Headquartered in the UK but with an established presence throughout Europe, Africa, the Middle East, Asia and Australia, RSK helps organisations around the world achieve their business aspirations in a sustainable and efficient manner.