British Columbia Mine Reclamation Symposium

Soilcover, a new computer model to aid in the design of soil cover systems for acid generating waste rock and tailings O'Kane, Mike; Wilson, G. Ward; Barbour, S. Lee


Evaluation of the flow of water across the soil atmosphere boundary is an essential component in the design of soil cover systems. The design of soil cover systems as oxygen barriers for the long term closure of sulphitic tailings and waste rock requires the accurate prediction of moisture fluxes between the cover surface and the atmosphere. SoilCover is a new software package which uses a theoretical method for predicting the exchange of water between the atmosphere and a soil surface. The theory is based on the well known principles of Darcy's Law and Pick's Law to describe the flow of liquid water and water vapour in the soil profile below the soil atmosphere boundary. A modified Penman formulation is used to compute the rate of evaporation to the atmosphere above the soil atmosphere boundary. SoilCover predicts the actual rate of evaporation from both saturated and unsaturated soil surfaces. The model accounts for atmospheric conditions, soil properties, and the effects of vegetation. In addition, SoilCover performs a water balance on the basis of infiltration, evapotranspiration, surface runoff, surface ponding, and the soil profile. The change in water content, suction, vapour pressure, temperature, and hydraulic conductivity with respect to time and depth within the soil profile are also calculated. SoilCover provides a one dimensional transient analysis which can be used interactively with other commercially available software packages for modelling groundwater flow in mine tailings and waste rock. The two dimensional flow system is modelled using the transient flux boundary conditions at the soil cover atmosphere boundary predicted by SoilCover.

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