Model for predicting soil suction via tensiometer cavitation curves: accounting for contact interface resistance and dynamic process of water flow

Accurate measurement of high soil matric suction is challenged by water cavitation in tensiometers, which produces cavitation curves instead of equilibrium data. Therefore, invert soil suction from cavitation curves is essential. In this study, we developed a modified tensiometer response model based on the Green–Ampt framework, which incorporates the time-dependent hydraulic processes at the ceramic cup–soil interface to represent the evolving contact resistance prior to complete hydraulic continuity. The model was validated against suction response curves measured by a T5x tensiometer in three soil types. Comparison with the Tsai's equation and Klute's equation demonstrates that the developed model incorporating contact interface resistance and water flow process provides superior soil suction prediction through tensiometer response curves. Furthermore, the developed model can successfully invert soil suction based on incomplete cavitation curves, attributed to its physically lag representation of the initial response. The predicted suction could even exceed the theoretical upper limit which determined by the air-entry value of the ceramic cup. The findings of this study provide theoretical support for improved accuracy in soil suction measurement and extended testing range of tensiometers.