Improving internal erosion resistance of silty sand using additives

Seepage-induced erosion, leading to piping, is one of the most common causes of failure for earth dykes, levees and dams. Various soil improvement (mixing) technologies can be employed to improve the internal erosion resistance of more troublesome soils. This paper describes the first steps in demonstrating nanoclay (montmorillonite) additive as a sustainable alternative to traditional soil additives for erosion-control applications. In this regard, the erodibility characteristics of standard Proctor (SP) compacted, very silty sand amended with 0·5–6% dry weight montmorillonite K10 (MK10) material was investigated at bench scale using the hole-erosion test (HET) apparatus. Parallel testing was performed on the same soil amended with 0·25–3% cement for comparison. Substantial erosion resistance improvements were achieved for as little as 0·5–1% MK10 content, comparable to cement addition, with the HET classification increasing from HET groups 1–2 for the highly erodible, compacted, very silty sand investigated to HET group 4 (moderately slow erosion) for the 1% MK10–soil mixture. Further investigations indicated the erosion resistance classification of the improved soil was not altered for under-compaction that achieved only 80% SP maximum dry density or for compaction at ± 2 percentage points from the identified SP optimum water content.