Bioremediation of Piping Erosion in Sand

This study aims to explore a remediation method in which organic soil is mixed with sand to increase the sand's resistance to piping erosion. Our preliminary experiments on internal erosion (piping and suffusion) of fibrous and amorphous peats (with organic contents of 23% and 32%, respectively) using rigid wall and flexible wall setups show that peat does not erode internally even when subjected to hydraulic gradients greater than those typically seen in the field. These initial investigations also suggest that mixing organic soils with erodible sand may reduce the potential for piping erosion. In this study, a mixture of green and manure compost, referred to as co-compost, is used as the source of organic soil. Hole-erosion tests are performed to quantify the erosion of a silty sand, the co-compost, and various ratios of sand—co-compost mixtures. The potential increase in consolidation settlement and reduction in shear strength and permeability due to the addition of organic matter are also investigated. Greater proportions of organic soil mixed with typical construction sand result in increased resistances to piping erosion. With the addition of organic matter to sand, consolidation settlement increases, undrained compression strength decreases, and permeability was reduced by two orders of magnitude.