Highly Organic Fill for Levee Stability Berms

Abstract

Earth berms constructed of cohesive fill are often used to improve the stability of levees. In some parts of the United States, many of the locally available cohesive soils contain high organic content (>9 %), which has historically prevented their use for stability berms. This study investigated the compaction characteristics, undrained strength, and erodibility of eight samples of clay from Louisiana with organic content ranging from 1.7 % to 29 % to evaluate their potential use for stability berms. The target total unit weight of 15.7 kN/m3 was found to be difficult to attain for soils with organic content above about 9 %. The desired minimum undrained strength of 19.2 kPa was easily attained for all of the organic content at water content up to 6 % wet of optimum. The erosion resistance, measured using the jet erosion test, stayed the same or increased as the organic content of the fill increased. Based on these test results, soils with organic content in excess of 9 % are suitable for use as stability berm fill, provided that a lower total unit weight can be used in design.