The design criterion for capillary barrier cover in multi-climate regions

The service performance of capillary barrier cover (CBC) under continuous rainfall is unclear, leading to a lack of the design criterion for CBC in humid regions. This study proposed a design criterion for CBC in multi-climate regions. First, the influence of fine layer thickness, initial water content and rainfall intensity on the performance of CBC under continuous rainfall was clarified through a soil column test. Subsequently, calculation models of effective water storage capacity and breakthrough time were derived based on test results. Finally, a design criterion for CBC in multi-climatic regions was proposed and verified. The main findings were as follows: (1) As expected, increasing the fine layer thickness and decreasing the initial water content enhanced the water storage capacity. Within the test range, the breakthrough time has a linearly positive, linearly negative, and negative power function relationship with the fine layer thickness, initial water content, and rainfall intensity, respectively. (2) The infiltration rate of CBC is controlled by saturated hydraulic conductivity under extremely continuous rainfall, and can be described by the equivalent infiltration rate. (3) The calculation results of the proposed water storage capacity and breakthrough time models are consistent with the test results, and the proposed design criterion is robust against various climates from drought to humidity. The research results can provide a reference for the design of CBC in multi-climate regions.