First saturation and resaturation of high capacity tensiometers with 1.5 MPa high air entry value (HAEV) ceramic filters

Mendes, J. and Gallipoli, D. and Toll, D.G. and Tarantino, A. (2018) First saturation and resaturation of high capacity tensiometers with 1.5 MPa high air entry value (HAEV) ceramic filters. In: PanAm Unsaturated Soils 2017. American Society of Civil Engineers (ASCE), Reston, Virginia, pp. 514-522. ISBN 9780784481684

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    Abstract

    High Capacity Tensiometers, or HCTs, are sensors that can measure negative pore water pressures (soil suctions) between -1.5 and -2 MPa. To achieve such measured values, HCTs first need to be fully saturated by water. For the first saturation of an initially dry HCT, the most common procedure involves application of vacuum followed by forced flooding by pressurised water. Instead, for the resaturation of a HCT that has cavitated (and is therefore still water flooded), only application of water pressure is necessary. Typically, the procedures for the first saturation and resaturation of HCTs can last days or weeks, which hinders adoption of these devices by the geotechnical industry. In this paper, faster procedures are presented for both first saturation and resaturation of HCTs built with 1.5 MPa air entry value filters. The duration of the first saturation can be reduced to less than 24 hours if high vacuum is first applied to the ceramic filter followed by water pressurisation at about twice the air entry value of the filter. Even more, resaturation of a cavitated HCT can be achieved in less than 10 minutes by simple water pressurisation of the ceramic filter. This is however true only if the HCT is not left to dry out to the atmosphere completely and is submerged in water just after cavitation.