Discussion of “Physical and numerical study of lateral diversion by three-layer inclined capillary barrier covers under humid climatic conditions”

Abstract

The authors investigated the performance of an inclined threelayer cover with capillary barrier effect (CCBE) system comprising silt, sand, and gravel, subjected to a continuous heavy rainfall (Zhan et al. 2014). They compared numerical results and analytical solutions with respect to effective length of lateral diversion of the inclined three-layer CCBE system. The comparison indicated that the analytical solution proposed by Stormont (1996) is relatively conservative. It should be noted that Stormont’s (1996) analytical solution is only applicable to a two-layer CCBE system. In the discussers’ opinion, this analytical solution should be modified to consider capillary effects contributed by both the upper two layers (i.e., silt–sand) and lower two layers (i.e., sand–gravel) in the three-layer CCBE system. The three-layer (silt—sand–gravel) CCBE system investigated by the authors can be simplified as the sum of silt–sand and sandgravel capillary barriers, as shown in Fig. D1. The infiltrated rainwater is first drained laterally along the silt–sand interface to the tip point at which the hydraulic conductivity of the sand layer is equal to that of the silt layer. Subsequently, rainwater flows into the sand layer and is drained laterally along the sand–gravel interface to the tip point at which the hydraulic conductivity of the gravel layer is equal to that of the sand layer. The lateral diversion length of the three-layer CCBE system, Lthree-layer, should be calculated as