Fiber Reinforcement for Waste Containment Soil Liners

The hydraulic properties of compacted clay liners can be adversely affected by desiccation cracking. Previous studies evaluated the use of soil additives (such as lime, cement, and sand) for crack reduction. Initial results indicated that soil shrinkage was reduced. However, in many cases, the additives resulted in an increased hydraulic conductivity and decrease in soil plasticity. As a result, there is an increasing interest in the use of fiber reinforcement, which has shown successful results in concrete and other material applications. The present investigation focused on the impact of fiber reinforcement on the development of desiccation cracks in compacted clay samples, as well as the impact of the fiber additives on soil workability, compaction characteristics and hydraulic conductivity. The results of this study indicate that, for the soils of this investigation, the optimum fiber content necessary to achieve maximum crack reduction and maximum dry density, while maintaining acceptable hydraulic conductivity, is between 0.4 and 0.5%. The observed crack reduction for this range of fiber content was approximately 50%, as compared to the unamended soil sample. The maximum observed crack reduction was approximately 90%, for a fiber content of 0.8%. Although the crack reduction could be increased further by increasing the fiber content, the sample hydraulic conductivity increased significantly and the practical limits of mixture workability were exceeded.