Effects of Short Polymeric Fibers on Crack Development in Clays

Many levees are constructed of clay soils which have a tendency to shrink and swell when subjected to periods of drying and wetting. Desiccation cracking occurs allowing percolation of rain water which may result in shallow surface slides. The purpose of this research was to assess the feasibility of using randomly distributed short polypropylene fibers to reduce the development of desiccation cracks in clay. Tests were conducted on laboratory prepared clays with a wide range of plasticity indices as well as natural clay samples. The fibers were effective in reducing the amount of desiccation cracking that occurs in clay samples. The fibers were effective in reducing the amount of desiccation cracking that occurs in clays subjected to drying. However, when subjected to wet/dry cycles, the fibers were not effective. The fibers increased the tensile strength of the clay and provided a ductile behavior that was not present in the samples without fibers. The fibers has no effect in reducing clay surface disintegration due to erosion. Limited testing with a grid-like fiber, with a bearing capacity failure in pullout as opposed to adhesion for the poly propylene fiber, indicated a modified fiber design could better interact with clays.