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| Experimental study on water storage capacity and breakthrough time of capillary barrier cover |
| LI Xiaokang1，LI Xu1，WANG Fei1，2，LIU Aqiang1，LIU Li1，LIU Yan1 |
| (1. Key Laboratory of Urban Underground Engineering of Ministry of Education，Beijing Jiaotong University，Beijing 100044，China；2. Department of Higher Education Publication，China Water and Power Press，Beijing 100038，China)
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Abstract The capillary barrier cover is maturely used in arid and semi-arid areas，but its service performance and design criteria in humid areas are less studied. In order to clarify the service performance of the capillary barrier cover under continuous rainfall，the relationships between the water storage capacity and the breakthrough time of the capillary barrier cover with the rainfall intensity，the thickness and the initial moisture content of the fine-grained soil layer were studied through the soil column infiltration test. The test results show that：(1) Decreasing the initial water content and increasing the thickness of the fine-grained layer can increase the water storage capacity. (2) Within the range of test thickness and moisture content，the breakthrough time decreases linearly with decreasing the initial water content while with increasing the fine layer thickness，and has a negative power function relationship with the rainfall intensity. Near the saturated permeability coefficient，the breakthrough time changes from a rapid decrease to a slow decrease with increasing the rainfall intensity. (3) Under extreme continuous rainfall，the infiltration rate of the capillary barrier cover is first controlled by the rainfall intensity，and finally tends to saturated permeability coefficient. This process can be described by the equivalent infiltration rate，which is significantly affected by the rainfall intensity and the initial water content. Based on the test results，a practical water storage capacity model and a semi-empirical theoretical model of the breakthrough time were proposed. The calculation results of the models are consistent with the test results，which illustrates that the proposed models can be used as the basis for the design of the capillary barrier cover in continuous rainfall. The research results can provide references for the design and maintenance of capillary barrier cover in humid areas and extreme rainfall conditions.
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2022, Vol. 41 
