Evaluation of a Geosynthetic Capillary Break
One of the major issues in the successful decommissioning of any waste disposal system is to mitigate the spread of contaminants into the surrounding environment. In many instances this is achieved by reducing amounts of net percolation and/or oxygen diffusion into the underlying waste. An engineered cover system incorporating a capillary break is a common solution to this problem. However, traditional soil capillary breaks can often be impractical for large facilities where desirable construction materials are not readily available.
The primary objective of this research is to show the initial steps in the development of a new type of geosynthetic product, namely a geosynthetic capillary break (GCB). This new product, composed of a nonwoven geotextile coupled with a fine-grained rock flour, will function similar to, and has the possibility of replacing traditional, soil capillary breaks in many applications.
The specific objectives of this research are to: i) determine the pertinent material parameters of the materials used to evaluate the GCB; ii) examine one-dimensional column testing of a typical engineered soil cover system incorporating the GCB; and iii) model the cover systems to better understand current performance and predict long-term performance of the GCB.
The GCB was evaluated based on the objectives outlined above. The material characterization consisted of the selection of suitable materials for the GCB, as well as the determination of their unsaturated properties. The results indicate that a geotextile-rock flour combination will develop a capillary break within an engineered cover.
The one-dimensional column tests evaluated four cover systems. Soil thicknesses of 30 and 60 cm were utilized, with one column of each cover thickness incorporating the GCB. The columns were tested under both high evaporative fluxes and high infiltration rates over the course of 111 days. The measured results show that there is less moisture movement in columns that incorporate the GCB.
A coupled soil-atmospheric finite element model was then used to develop a predictive model for the cover systems. The model was calibrated to the measured results from the column testing to ensure consistency. The parameters obtained from this model were used to evaluate an engineered cover system incorporating the GCB for a minesite in Flin Flon, MB. The results from the predictive modeling show that moisture infiltration is reduced approximately 80% when comparing columns with the same cover thickness. Oxygen diffusion is also reduced by 20 to 25% with the inclusion of the GCB.
School:University of Saskatchewan
School Location:Canada - Saskatchewan
Source Type:Master's Thesis
Keywords:capillary break engineered soil cover geosynthetic
Date of Publication:09/15/2005