Estimation of Interface Parameter for One-Dimensional Consolidation with Continuous Drainage Boundary Conditions

In conventional consolidation theories, a boundary is simulated as either perfectly pervious or impervious, where the time-dependent drainage capacity at the boundary is ignored. Using the time-dependent impeded boundary condition, it is very difficult to derive solutions analytically. A continuous drainage boundary is proposed in this investigation to characterize the time-dependent drainage behavior at the boundary. The interface parameter is of physical significance, which depends on the properties of both the consolidating soil and the adjacent medium. In this study, two methods are developed to estimate the interface parameter. Back-analysis can be conducted to evaluate the interface parameter based on the variations of excess pore-water pressure from experimental or field measurements. Alternatively, an empirical approach is derived to correlate the interface parameter with the ratio of the coefficient of consolidation and the thickness ratio between adjacent media. The solution is further employed to analyze layered soils with a horizontal drain. It is found that both the plane of maximum excess pore-water pressure and the optimal position of horizontal drain move toward the boundary with a lower drainage capacity with time. A simplified design chart is finally presented to optimize the layout of the horizontal drain in layered clay-drain systems.