Two‐dimensional Green–Ampt response of high‐capacity tensiometers and a conceptual pathway to correct dynamic water retention curve data

In the investigation of the relationship between measured soil suction and the rate of saturation change, an increase in response time prevents the tensiometer from instantaneously reacting to changes in suction. Solving this problem requires a tensiometer response model, which is based on the measured data from partial drainage and adsorption curve to obtain the potential actual suction related to the flow rate. Although several models have been developed for the calibration of low‐capacity tensiometers in recent decades, these models have not been effectively practiced on high‐capacity tensiometers. In this paper, we investigated the physics mechanism of tensiometer seepage, established a two‐dimensional infiltration equation based on the Green–Ampt model. Soil column experiments were conducted to investigate the applicability of the developed model for the curves obtained from Jingyang loess, Dingbian loess, and Maowusu sand. The results indicated that the developed model could fit the delayed stage and equilibrium stage of the response curves. Compared with Klute's equation and Tsai's equation, the proposed model had achieved an average reduction of 36.57%, 34.23% and 85.00%, 89.47% in the mean absolute error and root mean square error, respectively. This optimized improvement confirmed that the retention of L(t), introduction of R, and appropriate selection of K(hSW) together lead to better fitting performance. In addition, we found that the ceramic cup conductance (C) required consideration of the internal structure of the cup. This research contributes to refining infiltration theory of tensiometers and promoting the application of tensiometers in unsaturated soils.