On the effect of compaction on the progression of concentrated leaks in cohesive soils
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SHORT COMMUNICATION
On the effect of compaction on the progression of concentrated leaks in cohesive soils Arman Khoshghalb1
•
Mohammad Nobarinia2 • Joshua Stockton1 • Farhoud Kalateh2
Received: 2 May 2019 / Accepted: 13 July 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The purpose of this study is to conduct hole erosion tests (HETs) to better understand the progression of concentrated leaks in compacted soils. While samples with high levels of compaction have been extensively tested for their erosion characteristics in the literature, soils at lower compaction levels have not yet been extensively assessed. This study aims to better understand the internal erosion behaviours of low-compacted soils during the progression of concentrated leaks. To this end, compaction tests are performed on various mixtures of Sydney sand and kaolin clay samples at different compaction moisture contents (i.e. moisture content at the time of compaction) and compaction efforts. Optimum moisture contents for different compaction efforts are subsequently determined. Samples for the HET are then prepared at various compaction densities and moisture contents to obtain their rate of erosion due to concentrated leaks. Results from testing show that if appropriate moisture contents are used, low-compacted samples do not necessarily show higher erodibility potential. The results can help in the determination of the most cost-effective, yet stable, materials for use in practice, for example in the core of embankment dams. Keywords Compaction Concentrated leak erosion Earth dams Hole erosion test Piping
1 Introduction Internal erosion process in cohesive soils occurs due to the internal movement of water and consequent hydraulic removal of the soil material by the flowing water. Internal erosion can progress to cause a concentrated leak which occurs when the internal flow destabilises soils by flowing through an open macropore and preferential flow paths or ‘pipes’ that are developed. Some events such as embankment dam failures are found to be primarily caused by internal erosion and can have significant consequences to areas downstream. Studies on internal seepage erosion date back to the early 1900s (e.g. [2, 3]). Over time, numerous experimental methods have been developed to study the erosion & Arman Khoshghalb [email protected] 1
School of Civil and Environmental Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
2
Faculty of Civil Engineering, University of Tabriz, Tabriz, East Azerbaijan Province, Iran
phenomenon in soils. Early experimental methods were mainly qualitative, such as the Crumb test [6] and pinhole test [24], which were mainly focused on the dispersivity of cohesive soils rather the erosion process caused by the shear stress applied by the flowing fluid. Improved techniques were developed subsequently for more accurate and quantitative assessment of internal erosion phenomenon due to concentrated leaks [1, 13, 15, 16,
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