RSA Geotechnics carry out a range of in-situ testing and sampling techniques to supplement our site investigation services.
Groundwater and ground gas monitoring
Groundwater monitoring is carried out to obtain samples for laboratory testing or to monitor the water levels. The groundwater samples are recovered employing either a dedicated disposable hand held bailer or a mechanical down-hole submersible pump.
Gas monitoring is undertaken to determine the levels of methane, carbon dioxide, oxygen and other gases which can be generated by made ground or backfilled materials. The gas flow within the borehole is dependent on the atmospheric pressure at the time the readings are taken.
In-situ California bearing ratio (CBR) testing
The CBR test is typically undertaken for road, runways or car park pavement design to assess the strength of the sub-grade. The test involves driving a cylindrical plunger of a defined area into the soil at a uniform rate. This requires the use of a reaction load, (for example, a four wheel drive vehicle or mechanical excavator), to provide the force. Alternatively a profile of equivalent in-situ CBR can be measured using the dynamic cone penetrometer (DCP).
Plate bearing testing
Plate bearing tests involve jacking a plate of known dimensions against a reaction load, usually the underside of a track-driven excavator and recording the ground deformation. Separate tests are performed to assess the bearing capacity of the soil and the prediction of settlement characteristics. The modulus of sub-grade reaction can be measured and correlated with CBR which is useful for assessing gravelly material when a conventional CBR test is inappropriate.
Sand replacement density (SRD) testing
Sand replacement density tests are used to assess the in-situ density of the soil or compacted sub-base material. Unless otherwise specified the large pouring cylinder method is normally adopted. The tests are generally undertaken at ground level. In some circumstances the test may be carried out in shallow trial pits or trenches excavated up to approximately 1.0m deep; if the side walls of the excavation are prevented from collapse either by digging a safe angle or by shoring with timber or support systems.