Borehole Drilling Services
Accurate Ground Investigation Using Specialist Drilling Techniques
Boreholes form a fundamental part of many site investigations, providing detailed information about ground conditions at depth. Chelmer offer a comprehensive borehole drilling service, using a range of techniques to suit different ground conditions, site constraints and project requirements. These investigations support both geotechnical and environmental assessments and are a key component in the design and planning of construction projects.
A variety of drilling methods are available, allowing each borehole to be tailored to the specific objectives of the investigation. Chelmer are able to undertake Continuous Flight Auger (CFA) boreholes, Cable Percussive boreholes, Window Sampling boreholes and hand augered boreholes where appropriate. This flexibility ensures that suitable techniques can be selected based on access, required depth, ground conditions and the type of data needed from the investigation.
Drilling Capabilities and Depths
Chelmer’s drilling rigs are capable of achieving depths of up to approximately 70 metres, although most investigations are typically carried out between 5 and 30 metres depending on the project requirements. The number, depth and location of boreholes are determined by the purpose of the investigation, with guidance available to clients during the planning stage to ensure an appropriate scope of works is defined.
The ability to adapt drilling methods and depths allows boreholes to be used across a wide range of applications, from small-scale developments through to large commercial or infrastructure projects. Each borehole is carefully positioned and executed to maximise the value of the data obtained.
Sampling and In-Situ Testing
During drilling operations, both disturbed and undisturbed soil samples can be recovered for further analysis. These samples are typically sent to Chelmer’s in-house UKAS accredited laboratory, where a wide range of geotechnical and chemical testing can be undertaken to support the investigation.
In addition to sampling, boreholes also provide the opportunity to carry out in-situ testing at depth. Techniques such as Standard Penetration Tests (SPT) and Cone Penetration Tests (CPT) may be undertaken where mechanical drilling is used, allowing engineers to assess soil strength and behaviour directly within the ground.
This combination of sampling and in-situ testing ensures that both physical and analytical data can be obtained, providing a reliable basis for design and assessment.
Installations and Monitoring Applications
Once drilling has been completed, boreholes can be converted into a range of installations depending on the requirements of the project. These may include standpipes for groundwater monitoring, gas monitoring installations or deep datum points for movement monitoring. The ability to utilise boreholes in this way adds further value to the investigation, allowing ongoing monitoring to be carried out where necessary.
These installations are particularly important on sites where ground conditions may change over time, or where long-term monitoring is required to assess stability, groundwater behaviour or gas migration.
Boreholes for Subsidence Investigations
Boreholes are also a key element of subsidence investigations, where they are used to assess ground conditions beneath existing structures. In these cases, boreholes are typically drilled to depths ranging between 3 and 6 metres and are often carried out using hand augering techniques to suit restricted access environments.
Where ground conditions make hand drilling difficult, such as in granular soils, mechanical methods can be utilised to ensure the required depth is achieved. This flexibility allows investigations to proceed effectively regardless of site constraints, ensuring that sufficient information is obtained to support accurate assessment of ground movement and potential causes of subsidence.
In-situ testing may also be undertaken within these boreholes, with methods such as shear vane testing or Mackintosh probing used depending on the soil conditions encountered. These tests provide valuable insight into the strength and consistency of the subsoil, which is critical when assessing subsidence-related issues.