Modeling dependence among suction, moisture, and cracking of a novel biochar synthesized from weed species

Water hyacinth (WH), an invasive weed species, has found its utility in the synthesis of biochar (BC). BC is further being explored for geoenvironmental applications such as landfill covers, green infrastructure, etc. The soil-water retention curve (SWRC) and crack potential are two of the key inputs required for modeling the unsaturated soil behavior in these projects. However, the impact of BC on SWRC and crack potential and the dependence among these two properties have not been studied extensively. In this article, initially, the impact of BC synthesized from WH as a soil additive is studied in terms of SWRC (volumetric water content, θ_w and suction, ψ) and crack intensity factor (CIF). It is found that an addition of 5-10 % BC can increase the water retention capacity by 41 % and reduce the crack potential by 50 %. Thereafter, the joint distribution of SWRC and CIF is established using a trivariate copula approach. Based on the minimum Akaike Information Criterion (AIC), uniform distribution for CIF and θ_w and gamma distribution for ψ are found to be appropriate. For modeling the dependence structure, two commonly used elliptical copulas, namely, Gaussian and “t” are explored. The results indicate that the t copula provides a better fit than the Gaussian copula and can successfully be used to model the highly nonlinear dependence structure between SWRC and CIF.