Internal Erosion Failure of Uniform Sands under Confinement and Constricted Seepage Exit

Kuang-Tsung Chang,Han-Yu Wu,Kevin Zeh-Zon Lee

doi:10.3390/w12092417

Kuang-Tsung Chang, Han-Yu Wu + Show 1 more

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https://doi.org/10.3390/w12092417

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Abstract

Seepage water may move soil particles and cause internal erosion of soils, leading to sinkholes and the collapse of embankments and slopes. To account for the effects of confinement and constricted seepage exit, a test apparatus was developed to study the internal erosion of granular soils under various confining pressures, particle sizes, and sizes of the seepage exit opening. As indicated in the literature, the behavior of internal erosion has been largely studied by laboratory experiments and field investigations, and mechanical models that help describe the failure mechanism of internal erosion are less prevalent. A hydro-mechanical model that incorporates the fluid drag force and the shear strength of soil was therefore developed for quantifying the internal erosion experiments conducted in this study. The experimental results showed that the greater the confining pressure or the particle size, the greater the critical velocity; the greater the seepage exit opening, the smaller the critical velocity. The critical velocity predicted by the proposed hydro-mechanic model compares reasonably well with the experimental data. In addition to the confining pressure, particle size, and size of the seepage exit opening, the proposed model also showed that the friction angle and porosity of the soil are factors influencing the critical velocity, which is consistent with the experimental findings of this study.

Highlights

The detachment and transport of soil particles due to seepage-induced internal erosion have been attributed to the failures of embankment dams and foundations of buildings
When the confining pressure is without confinement, the erosion tests with confinement conducted in this study showed much more significant, such as in the foundation near the centerline of an embankment dam where a defect higher critical hydraulic gradients; Figure 12 shows the variation of the critical hydraulic gradient exists, a higher critical hydraulic gradient would be required to initiate an internal erosion failure
A test apparatus consisted of a high head cell, a specimen cell, and a confining cell was developed in this study

Summary

Introduction

The detachment and transport of soil particles due to seepage-induced internal erosion have been attributed to the failures of embankment dams and foundations of buildings. Three modes of internal erosion behavior have been identified: (1) backward erosion piping, (2) concentrated leak erosion, and (3) suffusion [2]. Richards and Reddy [2] mentioned that backward erosion piping occurs with seepage through intergranular flow in which a pipe develops progressively toward the upstream source of the seepage, and the concentrated leak erosion occurs along soil–structure openings or cracks through an embankment. Hillslope failure can be induced by seepage erosion; small-scale model tests and numerical analyses were performed by Crosta and di Prisco [3], and they found that the slope failure of a fluvial terrace was caused by the concentrated groundwater flow

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