Erosion Mechanisms of Organic Soil and Bioabatement of Piping Erosion of Sand

This paper presents the findings of a preliminary research program that aimed to investigate the mechanisms governing the progression of piping erosion in organic soils and attempted to use the findings to reduce the severity of piping erosion of sand. The hypothesis was that the presence of organics within mineral soils results in a reduction in piping erosion progression. Erosion behaviors of the soils were quantified using a simple erosion test with a preformed hole to simulate an initial piping channel. The research was split into five test phases. In Phase 1, the influence of grain-size distribution was eliminated to develop a preliminary understanding of the role that organic matter plays in the erosion process. The results indicated that organic matter likely contributed to a reduction in piping erosion. The second phase excluded both grain-size distribution and individual particle shape as variables in the erosion process. The results further confirmed the connection between organic matter content and erosion resistance. The third phase revealed the positive correlation between the reduced piping erosion and increased organic matter content. The fourth phase investigated the quantitative relationship between certain biologically derived substances (polysaccharides and glomalin) and piping erosion reduction. The positive correlations that were preliminarily derived from this phase indicated that these substances likely play a major role in reducing piping erosion. The final phase comprised of introducing organic matter into mineral soil and quantifying the subsequent changes in geomechanic properties. The results suggested that the introduction of organic materials into mineral soil decreases strength, increases consolidation settlement, and reduces permeability.