In-situ Testing

Standard Penetration Test

SPT

The Standard Penetration Test is one of the most widely specified in-situ tests in UK ground investigation. A 63.5kg weight is dropped over a calibrated distance of 760mm, and the number of blows taken to drive the sampler over a set distance is recorded, giving a direct measure of the ground's resistance. Several of our rigs carry rig-mounted SPT hammers, which keeps the test consistent and takes the manual handling out of it.

Dynamic Probe Test

DPT

For a rapid, continuous profile of ground resistance, the Dynamic Probe Test drives a sacrificial cone into the ground - a 50kg weight over a calibrated distance of 500mm, again recording the blows taken over a set distance. It is a quick, cost-effective way to profile a site and target where further investigation is needed.

Undisturbed sampling

U100 & U70

Where the design needs samples that keep the ground's structure intact for laboratory testing, we take undisturbed U100 and U70 samples, using either thin-walled (class 1) or standard undisturbed sample barrels. Taken through the borehole as drilling proceeds, these preserve the soil as it sits so its strength and stiffness can be measured properly.

Specialist testing

A wider in-situ and hydrogeological suite

Alongside the tests carried out through our boreholes, we undertake a range of specialist in-situ and hydrogeological testing to suit the scheme:

• California Bearing Ratio (CBR) - the strength and load-bearing capacity of subgrade and pavement foundation materials, the primary input for flexible pavement and road thickness design.
• Plate load testing - in-situ bearing capacity and stiffness (deformation modulus) for shallow foundation, pavement and embankment design, and to verify formation acceptance.
• TRL Dynamic Cone Penetrometer (DCP) - rapid, low-cost strength profiling of subgrade and unbound pavement layers with depth, flagging weak zones and variability across a site.
• Lightweight Deflectometer (LWD) - quick, repeatable quality control of compaction and stiffness on fill, capping and subgrade during earthworks.
• Soakaway / infiltration testing (BRE Digest 365) - soil infiltration rates to confirm the ground suits soakaways or SuDS and to size those systems correctly for surface-water disposal.
• Packer (Lugeon) testing - the permeability and hydraulic character of jointed or fractured rock, informing grouting, dam, tunnel and groundwater-control design.
• Borehole permeability - falling, rising and constant head - the in-situ hydraulic conductivity of soils for dewatering, drainage and foundation design, and assessment of groundwater flow and contaminant migration.
• Peat probing - the depth, thickness and extent of peat and soft organic deposits, for earthworks volumes, ground-improvement design and foundation selection in peatland.

Methods and applicable standards - for example BS 1377, BS 5930, BRE Digest 365 and TRL Overseas Road Note 31 - are confirmed against the specific project requirements and site conditions.