Multilayered Capillary Barrier Systems: Analytical, Numerical, and Experimental Study

Capillary barrier systems (CBSs) are geotechnical structures that are used to limit rainwater infiltration into the underlying soil. The conventional layout of CBSs consists of a finer-grained layer overlying a coarser-grained layer. The use of multilayered CBSs (MCBs) consisting of multiple pairs of finer and coarser layers can be used to improve the water storage capacity (WSC), and hence the effectiveness, of these systems. Four column infiltration tests with a slow infiltration rate of 1.3×10−7 m/s were carried out and these demonstrated (1) that a significant gain in WSC can be achieved by using MCBs compared to conventional single CBSs (up to 40% in the specific tested cases); and (2) the existence of an optimum number of layers that maximizes the gain in WSC (three pairs of finer- and coarser-grained layers in the specific tested cases). Although values of WSC achieved if the finer layer material is relatively coarse will always be lower than those achieved if the finer layer material is finer, the difference can be reduced by the use of multilayered CBSs. A simple analytical method for the design of horizontal MCBs is proposed and then validated by comparison with the results of the column infiltration tests and rigorous FE analyses. A parametric analysis was undertaken to examine the effect of the number and thickness of layers, materials, and infiltration rate on the water storage capacity of horizontal MCBs.