Abstract
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.
Highlights
IntroductionThe most common causes of failure for hydraulic earth structures (e.g. dykes, levees and dams) are internal erosion and piping induced by seepage flow, accounting for 46% of the 11 192 case-study embankment dam failures investigated by Foster et al (2000)
After overtopping, the most common causes of failure for hydraulic earth structures are internal erosion and piping induced by seepage flow, accounting for 46% of the 11 192 case-study embankment dam failures investigated by Foster et al (2000)
This paper presents hole-erosion test (HET) investigations on the use of commercial montmorillonite K10 (i.e. MK10) additive for achieving improvements in the hydraulic erosion resistance of standard Proctor (SP) compacted, very silty sand material
Summary
The most common causes of failure for hydraulic earth structures (e.g. dykes, levees and dams) are internal erosion and piping induced by seepage flow, accounting for 46% of the 11 192 case-study embankment dam failures investigated by Foster et al (2000). Preferential flow paths can develop within compacted earth-fill and (or) foundation materials on account of defects arising from hydraulic fracturing, cracking, plant roots and so on, with the resulting water flow detaching soil particles, leading to the formation and evolution of a continuous ‘pipe’ (piping) between the upstream and downstream sides Laboratory investigations, such as those performed using the hole-erosion test (HET) (after Wan and Fell, 2002, 2004a, 2004b), provide insights of the internal erosion (piping) characteristics of soil testspecimens in terms of quantifying their critical hydraulic shear stress (τc), coefficient of erosion (Ce) and erosion rate index (IHET) parameter values. The HET method simulates smallscale progressive internal erosion in the test specimen by causing erosive enlargement of a horizontal predrilled hole on account of internal flow through the hole under a controlled
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