Australian Research Council Centre of Excellence Geotechnical Science and Engineering

Soil, Water and Air Sampling and Monitoring Techniques

Sampling of Ground Water and Gas

The testing facility is equipped with a BAT ground water sampling and monitoring system. The system allows for quick, discrete sampling of both liquid and gas phases at specific depths. The sampling module can be inserted using the same apparatus used to push the cone penetrometers. The BAT module is applicable for use in both saturated and unsaturated soil profiles.

After pushing the sampling probe to the required test depth, the push rods are then retracted by 200mm to expose the sampling screen from behind the sealed shield. An evacuated sample vial is lowered through the hollow centre of the push rods until the vial makes contact with a double ended needle which connects the vial and the filter tip. Any number of vial samples can be taken and recovered from a single test depth, to ensure adequate sample size and representation, before pushing to a new test depth.

All elements of the BAT system, including the encapsulated samples, are hermetically sealed preventing loss of volatile components. A sealed shield protects the filter tip during delivery of the probe. This shield is retracted at the point of sampling to prevent cross contamination of samples during penetration.

Soil Pore Pressure Measurement

The BAT system can perform ground water pressure measurements. An electronic pressure transducer allows the BAT module to accurately measure both negative and positive ground water pressures at the position of the filter tip. Pressure measurements in the range from -10m to 150m can be determined to a resolution of 10mm of water column.

Soil Permeability Measurement

The BAT system allows for routine testing of in-situ permeability. Testing involves measuring the rate of flow into or out of a sample container. Flow rates are computed by monitoring the pressure change in the container and using Boyle’s law to convert the pressure change to a volumetric change. Analysis of the time-pressure record yields the coefficient of permeability.