Local moisture monitoring of unsaturated triaxial silty sample by a four-probe method based on van der Pauw configuration

• Published in: Acta geotechnica Vol. 18; no. 5; pp. 2813 - 2825
• Main Authors: Ma, Deliang, Xie, Yifei, Lan, Tianyang, Chang, Jianmei, Feng, Huaiping
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2023; Springer Nature B.V
• Subjects: Complex Fluids and Microfluidics; Configurations; Contact pressure; Electrical resistivity; Electrodes; Engineering; External pressure; Foundations; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Moisture content; Moisture effects; Monitoring; Research Paper; Soft and Granular Matter; Soil moisture; Soil Science & Conservation; Solid Mechanics; Temperature; Testing; Triaxial tests; Water content; Four-probe method; vdP configuration; Resistivity; Soil moisture monitoring; Unsaturated triaxial apparatus
• ISSN: 1861-1125; 1861-1133
• DOI: 10.1007/s11440-022-01719-x

The resistivity is a prevalent way to determine the soil moisture content in unsaturated triaxial test. However, the limited space of the unsaturated triaxial apparatus limits the configuration and sensor size. In the study, a novel local moisture monitoring in the unsaturated triaxial test is proposed by a novel four-probe method based on the concept of the van der Pauw configuration. The measurement system (automatic testing device, flexible printed electrodes) was designed, and external factors of contact pressure and temperature were investigated. Finally, the local moisture monitoring performance was verified. The obtained results indicated that electrodes required the 140 kPa prepressing process to contact fully, and 20 kPa minimal contact pressure was required to hold the contact state. Before testing resistivity, a constant temperature process for at least 1.5 h in the outer room helps improve the result reliability. The relative error of moisture monitoring was lower than 5% within 6 – 18% moisture content of the unsaturated triaxial sample, with high accuracy in the undrained unsaturated triaxial test.