The following is the first draft of an academic paper. Please help me polish the language.
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title: Experimental study on 3D geometric characteristics of the pipe of dike backward erosion piping
Abstract: The geometric dimensions of pipe formed during backward erosion piping (BEP) are of great significance for understanding the mechanism of BEP and numerical simulations. At present, relevant research mainly focuses on the two-dimensional morphology of pipes, and there is a shortage of sufficient understanding of three-dimensional (3D) characteristics of the pipe. To study the 3D geometric characteristics of the pipe, this paper measures and analyzes the 3D size of the pipe using gypsum injection method and 3D laser scanning method, and the variations in pipe depth, width, ratio of width to depth are investigated in detail. A mathematical model for pipes size is established, and the influence of the roughness of cover plate as well as the compactness of sand on the 3D geometry of pipe is clarified. It is found that the cross-section of the pipe is approximately rectangular, with the horizontal scale being much larger than the vertical scale. As the length of the pipe increases, the depth and width of the pipe gradually decrease, and the relationship of the pipe depth and width with the pipe length could be fitted by linear functions. The roughness of cover plate has a significant impact on the size of pipe, and a smooth cover plate caused a certain deviation in experimental results of the pipe size.
Keywords: Dikes; Backward erosion piping; Pipe; 3D Geometric Characteristics
1 Introduction
Backward erosion piping (BEP) is an internal erosion mechanism that can destabilize dikes and embankments founded on a granular aquifer covered by a cohesive layer. [1] BEP occurs when a concentrated seepage flow towards a local disruption of the downstream top layer. This paper focuses specifically on the type of BEP that occurs in the granular foundation of dikes consisting of uniform sands, and covered by a cohesive layer. With the development of BEP, shallow pipes in the upstream direction below the cohesive layer would be formed. When a pipe reaches the upstream water level, the flow through the pipe increases significantly, causing severe erosion, which may lead to the collapse of embankment. [2-5].
The pipe dimensions of the pipe have a significant influence on the results of the hydraulic analyses of water and sediment flow through the pipe and groundwater flow towards the pipe [6]. Moreover, the correct estimation of pipe dimensions is important in numerical simulations of pressure distribution in the pipe and upstream of the pipe [7], which is in turn important for the correct understanding of the piping process. Hanses [8] analyzed the pipe dimensions and concluded that the pipe width near the tip was constant with experimental methods. Van Beek et al. [9] studied pipe depth by evaluating the volume of sand that was ejected to the surface, and they found that the average depth remained constant during lengthening. Moreover, the variation of pipe widths in relation with the grain size was studied [10]. Vandenboer et al. [11,12] demonstrated that backward erosion piping should be treated as a three dimensional phenomenon rather than a two dimensional problem in terms of pipe development. However, the existing research on pipe dimensions is mainly two-dimensional study. [13-15]. Akrami [13] proves that the two-dimensional study of the pipe in a line (pipe depth along the pipe length) cannot show conclusive results about the pipe geometry and the erosion mechanism. The pipe therefore should be studied in three dimensions rather than two dimensions.>