Trial Pits & Boreholes

Trial pits and boreholes are the most common techniques used in ground investigations.

Trial Pits can be excavated either by hand or machine depending on project requiremenrts.

  • Machine excavated pits

    are a cost-effective way of making rapid assessment of the shallow ground and groundwater conditions across a wide area. Samples can be obtained and in-situ testing carried out, including:

    • Hand shear vane
    • In-situ density
    • CBR / plate bearing
    • Soakaway (to BRE Digest 365)
  • Hand excavated trial pits

    are used in sensitive locations to minimise the risk of damage to foundations or services.


Harrison Group uses a range of drilling techniques for investigation and monitoring purposes, on land and over water. Our site personnel have NVQ drilling qualifications, along with CSCS and PTS training, and all equipment complies with current health and safety requirements.

Boreholes allow soil and water samples to be taken for geotechnical and environmental testing. A range of in-situ tests can be carried out and instrumentation installed to monitor groundwater, leachate, gases and ground movement.

  • Cable percussive drilling

    is used for boreholes in superficial deposits such as clays, sands, gravels and weak rock.

  • Rotary drilling

    , using wheeled or tracked rigs, can penetrate very dense materials or rock. The technique allows continuous core samples to be taken for logging and testing.

  • Dynamic continuous (‘window’) sampling

    is a versatile method of drilling small diameter boreholes using hand-held, wheeled or tracked equipment, which is ideal for limited access locations.