Geotechnics Limited has invested in a variety of in-situ testing and specialist sampling equipment to supplement the standard range of site investigation rigs. This allows the company to offer a comprehensive service in most environments and sites.
We are able to use any of the following in-house resources...
The dynamic probe provides a rapid and cost-effective preliminary means of assessing ground conditions, particularly on sites with difficult access, limited headroom or slopes. Testing provides a vertical profile of blow count for successive penetrations of 0.1m and probing depths of 5 to 10m are routinely achieved and greater depths are possible in suitable strata.
Probing can be used before, as part of or after a main investigation to supplement the data obtained.
Piezometers can be installed with this equipment to allow long-term monitoring of groundwater levels. Similarly, gas monitoring tubes can be installed in or adjacent to contaminated sites where environmental considerations are of concern.
Windowless samples are taken using the dynamic probe apparatus or a hand-held percussive device, both of which drive steel tubes into the ground in 1m lengths. Samples are normally retrieved in the plastic liners, although traditionally, window sampling means samples are taken from a "window" in the side of the hole. The hole is not normally cased and progress depends on the nature of the strata penetrated. The portable kit can be carried by an individual and used in any headroom where the operative can function. Geotechnics has used this system on many railway projects. Standard penetration tests can be undertaken using the terrier rig, which can also install casing.
In-situ CBR and DCP Tests
In-situ California bearing ratio (CBR) equipment drives a plunger to penetrate soil at a given rate. The relationship between force and penetration is calculated and plotted graphically on the records and a comparison is made to the behaviour of a standard material to give the CBR of the tested soil at certain values of penetration.
The in-situ dynamic cone penetration (DCP) test comprises the measurement of increments of penetration of a 60° cone driven into the ground using an 8kg hammer falling a distance of 575mm. An indicative CBR value is obtained from a relationship between CBR and the DCP readings, as derived by the Transport Research Laboratory. This method can be used as a cost-effective preliminary assessment of a site where formation levels have not been determined.
In-situ Density Tests
These can be undertaken using sand replacement and core cutter techniques. Nuclear density and moisture content monitoring can be provided by arrangement.
Gas and Groundwater Monitoring
Routine gas monitoring of well installations, including methane, carbon dioxide, oxygen, barometric pressures, hydrogen sulphide and carbon monoxide are carried out using a range of in-house equipment at all regional offices.
Groundwater monitoring in standpipes or piezometers is undertaken using dip meters and the presence of hydrocarbons by interface meters.
Gas and groundwater sampling from wells is frequently undertaken for laboratory testing purposes.
Variable (falling and rising) head tests can be undertaken in boreholes or through standpipes/piezometers.
Packer permeability testing can be undertaken in boreholes using pneumatic packers.
Soakaway (infiltration) tests in trial pits can also be undertaken in accordance with BRE Digest 365. It should be noted that all permeability testing is time dependent and suitable allowance provided for testing in low permeability soils and rocks.
In-situ Water Testing
A range of in-situ surface water and groundwater quality tests for pH, electrical conductivity, temperature, redox tests and turbidity and dissolved oxygen are regularly undertaken.