Wenhao Jiang

Heavy rainfall is a common natural phenomenon. Regarding the issue of water infiltration in an infinite vegetated slope (consisting of rooted and unrooted layers) under the heavy rainfall condition, the infiltration process is divided into two stages— before and after the slope surface reaches saturation—and the corresponding analytical solutions are acquired through several mathematical approaches. Then the proposed solutions are effectively verified by two comparisons. Finally, based on the factor of safety ( F s ), the effects of key factors on the slope’s shallow stability are quantitatively investigated, and some novel findings are obtained. For example, an increased heavy rainfall rate reduces the F s , but this effect exhibits a tendency of increasing and then decreasing. An increase in transpiration rate enhances the infinite vegetated slope’s whole stability, while its influence will be declined after the heavy rainfall infiltration. The increased root tensile strength improves the F s within the rooted layer, but does not affect the unrooted layer’s stability. Moreover, compared with the “exponential” root shape, the F s within the unrooted layer is slightly lower in the case of the “uniform” root shape. Overall, the findings provide useful insights into infiltration mechanisms and shallow stability of infinite vegetated slopes under heavy rainfalls.

Vegetated landfill covers (VLC) are extensively applied to block rainwater infiltration and reduce the leachate generation. However, the associated analytical works remain limited. This study, for the first time to our best knowledge, develops analytical solutions for transient infiltration of water in the VLC (consisting of rooted and unrooted layers) under a time-varying rainfall scenario, incorporating the natural evaporation effect. Then, key expressions of an analytical solution under several common rainfall patterns are presented. On this basis, the obtained solutions are validated through two comparisons. Finally, the conducted application study finds that, among the five rainfall patterns with equal total rainfall, the “prepeak” rainfall pattern induces the largest cumulative bottom percolation C Q b . An increase in evaporation rate decreases the C Q b , and such effect gradually grows over time. Among different initial water content forms, the form with a larger bottom water content will lead to a larger C Q b , but this impact mainly occurs in the early stage of the rainfall event. For four classic root architectures considered, the VLC is most effective in blocking bottom water percolation with the uniform root architecture, while it is least effective with the exponential root architecture. Further, the VLC’s effectiveness in blocking bottom water percolation has been observed to become stronger with the increase of rooted layer thickness and transpiration rate, and such function is more effective than that of a soil-based landfill cover with no root. Overall, this analytical investigation can take into account the combined effects of time-varying rainfall feature and natural evaporation and contribute to guiding the application and design of VLCs.

Both temperature change and consolidation behavior affect the transport of organic contaminants in compacted clay liners (CCL) at the bottom zones of landfills, but the mechanisms of their ...

Contaminant transport in soil-water systems is a central issue in groundwater protection and hydrological risk assessment. This study develops concise analytical solutions for two-dimensional contaminant transport in infinite and finite domains. The infinite-domain solution is formulated for direct concentration prediction, whereas the finite-domain solutions account for Dirichlet and Neumann right-boundary conditions. The solutions explicitly include advection, molecular diffusion, mechanical dispersion, adsorption, and first-order degradation, and avoid numerical Laplace inversion. They are verified through comparisons with existing analytical solutions, finite-difference simulations, and mutually consistent limiting cases. The applicability of the infinite-domain solution to finite hydrological domains is then quantified by defining regions where prediction errors are negligible. Results show that the infinite-domain solution overestimates concentrations when the finite right boundary is Dirichlet, but underestimates concentrations when it is Neumann. Prediction errors increase with horizontal distance and decrease as domain thickness increases. A landfill leachate example demonstrates how the solution can estimate contamination scope and migration distance. The proposed solutions provide benchmark tools for hydrological solute transport modelling and preliminary assessment of soil and groundwater contamination.