Interface Of Soil Layers Research Articles

Handling the water content discontinuity at the interface between layered soils within a numerical scheme

In general, the water content (θ) form of Richards’ equation is not used when modeling water flow through layered soil since θ is discontinuous across soil layers. Within the literature, there have been some examples of models developed for layered soils using the θ-form of Richards’ equation. However, these models usually rely on an approximation of the discontinuity at the soil layer interface. For the first time, we will develop an iterative scheme based on Newton’s method, to explicitly solve for θ at the interface between 2 soils within a numerical scheme. The numerical scheme used here is the Method of Lines (MoL); however, the principles of the iterative solution could be used in other numerical techniques. It will be shown that the iterative scheme is highly effective, converging within 1 to 2 iterations. To ensure the convergence behaviour holds, the numerical scheme will be tested on a fine-over-coarse and a coarse-over-fine soil with highly contrasting soil properties. For each case, the contrast between the soil types will be controlled artificially to extend and decrease the extent of the θ discontinuity. In addition, the numerical solution will be compared against a steady-state analytical solution and a numerical solution from the literature.

Using a finite element grid on corner points in flow models

One of the main functions of a multilayer cover liner is to prevent water from infiltrating into mine or other waste thereby preventing the occurrence of ground water pollution. In the past, numerical models have predominantly dealt with vertical infiltration or infiltration into sloping hillsides of infinite extent. The two layer model investigated in this paper has a more realistic shape which is piece-wise linear with a horizontal top, vertical bottom and a sloping section in-between. At the intersection of these segments are corner points where there are changes from sloping flow dynamics to either vertical or horizontal flow dynamics, depending on the corner point. The abrupt change in dynamics at the corner points can cause numerical problems especially when dealing with the boundary condition at the interface of two soils. This paper will deal with the corner point problem at the soil layer interface and, in particular, investigate the use of a finite element grid around the corner points.

The numerical solutions of Green's functions for transversely isotropic elastic strata

In this paper, a model of transversely isotropic elastic strata is used to simulate the soil layers situated on a half space. Instead of the half space, an artificial transmitting boundary is used to absorb the vibration energy. The displacement formulas at any soil layer interface under vertical or horizontal harmonic ring loads are obtained by using the thin layer element method. From these formulas, the explicit solutions of Green's functions—the displacement responses at any interface of these strata under vertical and horizon harmonic point loads—are derived. The examples show that the method presented in this paper is close to the theoretical method and the transversely isotropic property has evident influence on the Green's functions.