UNSATURATED FLOW THROUGH SOLID WASTE LANDFILLS: MODEL AND SENSITIVITY ANALYSIS

: The movement of precipitation water infiltrating through the material (refuse) of solid waste landfills is examined via numerical solution of the equations of continuity, and motion (Darcy's Law). The solution of the equations is obtained by a fully implicit, finite-difference scheme. Both unsaturated and saturated surface conditions are considered, making the scheme suitable for real-time simulation of net precipitation and moisture redistribution events. A sensitivity analysis showed that for unsaturated surface conditions the solution is primarily affected by hydraulic conductivity and capillary diffusivity, and is relatively independent of the space and time steps. In addition, the precipitation averaging process is shown to be critical in the correct computation of moisture transport during the time period where the transition from unsaturated to saturated conditions occurs. The model presented herein is suitable for analysis of water movement through landfills, and the design of bottom collection systems.

[1]  C. Braester.  Moisture variation at the soil surface and the advance of the wetting front during infiltration at constant flux , 1973 .

[2]  Edward G. Nawy,et al.  Modeling for design of landfill bottom liners , 1984 .

[3]  Gaylon S. Campbell,et al.  A SIMPLE METHOD FOR DETERMINING UNSATURATED CONDUCTIVITY FROM MOISTURE RETENTION DATA , 1974 .

[4]  J. Philip.  THE THEORY OF INFILTRATION: 1. THE INFILTRATION EQUATION AND ITS SOLUTION , 1957 .

[5]  Edward G. Nawy,et al.  Moisture Transport in a Solid Waste Column , 1984 .

[6]  E. C. Childs,et al.  The permeability of porous materials , 1950, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[7]  Y. Mualem,et al.  Hydraulic conductivity of unsaturated porous media: Generalized macroscopic approach , 1978 .

[8]  W. Brutsaert.  The concise formulation of diffusive sorption of water in a dry soil , 1976 .

[9]  D. K. Babu.  Infiltration analysis and perturbation methods: 1. Absorption with exponential diffusivity , 1976 .

[10]  G. Hornberger,et al.  Empirical equations for some soil hydraulic properties , 1978 .

[11]  J. Parlange,et al.  A parameter‐efficient hydrologic infiltration model , 1978 .

[12]  J. Philip,et al.  THE THEORY OF INFILTRATION: 2. THE PROFILE OF INFINITY , 1957 .

[13]  W. R. Gardner.  SOME STEADY‐STATE SOLUTIONS OF THE UNSATURATED MOISTURE FLOW EQUATION WITH APPLICATION TO EVAPORATION FROM A WATER TABLE , 1958 .

[14]  L. Ahuja.  A Numerical and Similarity Analysis of Infiltration into Crusted Soils , 1973 .

[15]  R. J. Hanks,et al.  Numerical Solution of the Moisture Flow Equation for Infiltration into Layered Soils 1 , 1962 .

[16]  P. Dass,et al.  Leachate Production at Sanitary Landfill Sites , 1977 .

[17]  D. K. Babu.  Infiltration analysis and perturbation methods: 3. Vertical infiltration , 1976 .

[18]  Michel Vauclin,et al.  A note on estimating finite difference interblock hydraulic conductivity values for transient unsaturated flow problems , 1979 .

[19]  J. Rubin,et al.  Soil Water Relations During Rain Infiltration: I. Theory1, 2 , 1963 .

[20]  S. Irmay,et al.  On the hydraulic conductivity of unsaturated soils , 1954 .

[21]  David L. Freyberg,et al.  Infiltration under rapidly varying surface water depths , 1980 .