A novel modeling method for the bimodal soil-water characteristic curve

This paper introduces a hypothesis to link the soil pore size distribution curve (PSDC) to the bimodal soil-water characteristic curve (SWCC). The relationships between the PSDC and the bimodal SWCC equations are discussed extending a novel modeling method using two equations; namely, the rigid equation and the simplified equation extending two well-known traditional unimodal SWCC equations from the literature. The calibration processes built for both the equations performance was evaluated for various types of soils. The results suggest that both the modified equations provide excellent comparisons with the measured data. The rigid equations provide comprehensive information about the macropores and the micropores of the bimodal SWCC; however, the simplified equations facilitate a flexible and simple curve-fitting process. The relationships between the proposed equations and the available methods for the bimodal SWCC from the literature are also discussed. In addition, a technique is developed based on regression analysis to estimate the key features for bimodal SWCC without bias. Similar to the unimodal SWCC equations the proposed equations are promising tools for predicting the properties of unsaturated soils; they are also valuable for use in numerical techniques for addressing complex nonlinear problems in engineering practice for unsaturated soils.

Automated summary

This study introduces two new equations to link soil pore structure to the soil-water characteristic curve, with one providing detailed information about bimodal SWCC and the other offering a flexible and simple curve-fitting process. A technique was also developed to estimate key features of bimodal SWCC without bias.