Towards the development on new high capacity tensiometers capable of measuring soil matric suction beyond 3 MPa

Abstract

High capacity tensiometers (HCT) are the only type of sensors in existence that can measure soil matric suction directly and are regarded to be the most accurate and reliable technique for the study of suction evolution in unsaturated soils. The measurement with HCTs is possible due to their design, composed of ceramic filter with a specific air entry value (AEV), small water reservoir, and pressure transducer. Where, the AEV of the ceramic filter, more precisely the largest pore size within the ceramic, plays the most important role in controlling the measuring range of HCTs. Specifically, decreasing the largest pore size within the ceramic results in an increase in the measuring range. In this work, a new development in HCTs is presented whereby the ceramic filter in HCTs was replaced from the typically used 1.5 MPa AEV ceramic filter with a new alumina ceramic filter with an estimated AEV of 3.5 MPa. To assess the performance of the new ceramic filter, similar designed HCTs were assembled with the Soilmoisture Equipment Corp. 1.5 MPa AEV and the new alumina ceramic filters. Early results show that the maximum measuring matric suction range is beyond 3 MPa for HCTs assembled with the new alumina ceramic filter.