Laboratory measurements of soil suction can be used to assess sample quality, desiccation and in situ stress. Soil suction can also be used to assess the effectiveness of different in situ compaction procedures.
Direct observations of large soil suctions can be made using suction probes. Suction probes are unique in their ability to make direct measurements over a wide range of soil suctions (e.g. up to 1800 kPa) and have been used extensively in both laboratory and field applications for a variety of clients and on a wide range of soil types throughout the world. Suction probes are widely acknowledged as a milestone in the measurement of soil suction and are actively contributing to a better understanding of the influence of suction on soil behaviour.
Measurements can be made on extruded samples or on soil whilst it is still inside a sample tube. In situ measurements can be made inside boreholes at shallow depths.
Soil samples are prepared and placed on a pedestal in which a suction probe is embedded. Each pedestal is then covered to prevent the sample drying.
Measurements can also be made whilst the soil is still inside the samples tube. This is useful for loose soils that are likely to lose their structure during extrusion.
Suction probes respond rapidly, with full equilibrium normally being reached within 24 hours. All of the recorded data is stored on a computer. Suction probes are calibrated using a UKAS accredited dead weight calibrator. Suction probes give better repeatability and are less operator dependent than other measurement techniques.