Analysis of the Critical Hydraulic Condition of Subterranean Soil Erosion and Its Factors
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ORIGINAL PAPER
Analysis of the Critical Hydraulic Condition of Subterranean Soil Erosion and Its Factors Fuwei Jiang
. Zhengde Guan
Received: 2 October 2017 / Accepted: 6 July 2020 Ó Springer Nature Switzerland AG 2020
Abstract Subterranean soil erosion is a common form of soil failure that is caused by groundwater seepage. In this paper, we present a subterranean soil erosion model ideally supposed as pipe flow with four conditions. By using the theories of pipe flow, its critical expressions are derived, including the critical flow quantity (Qcr), the critical velocity (Vcr), and the hydraulic gradient (Icr). A simulating experiment is designed to test Qcr to calculate the other critical values. In a case study, 14 clay samples from Guiyang, Guizhou, China, are tested via a simulation experiment. As a result, the critical shear stress of samples is found to be 32.01 Pa. Furthermore, three critical values of suffusion, including Qcr, Vcr and Icr, are calculated with different diameters of soil pores by using the critical expressions. Analyzing the relationship among the values shows that the pore diameter and groundwater temperature influence the critical hydraulic condition of subterranean soil erosion. Keywords Subterranean soil erosion Pipe flow Hydraulic condition Pore diameter
F. Jiang (&) Guizhou Institute of Technology, Guiyang 550003, China e-mail: [email protected] F. Jiang Z. Guan Institute of Karst Geology, Chinese Academy of Geological Science, Guilin 541004, China
1 Introduction Soil erosion is a common form of soil failure caused by groundwater seepage. Present research on soil erosion focuses on superficial soil erosion (Markhi et al. 2019; Cuca and Agapiou 2018; Altieri et al. 2018; Fenta et al. 2016; Sobol et al. 2017; Elaloui et al. 2017). However, subterranean soil erosion has not been widely addressed, though it is common and widely distributed, especially in limestone regions (Gerstenhauer 1978; Keqiang and BinW 2004; Wang et al. 2014), and has not been considered in predictive models such as USLE, WEPP, and SIDASS (Wischmeier and Smith 1978; Lane and Nearing 1989; De et al. 2005). The hydraulic condition is the main factor leading to subterranean soil erosion. Generally, the hydraulic conductivity (K) and the hydraulic gradient (I) are two traditionally classic values used to assess subterranean soil erosion. However, K is difficult to detect with high accuracy owing to the large-pore system (Bouma and Wo¨sten 1979; Germann and Beven 1981), the effect of measuring scale (Messing and Jarvis 1995), freezing– thawing and drying–wetting cycles (Graham et al. 2001), overlying soil (Fox et al. 2000), chemical composition (Zhang and Norton 2002), and water content (Berilgen et al. 2006). It is also difficult to measure the functional relationship between K and the water level (H) (Bouma and Wo¨sten 1979; Germann and Beven 1981; Mualem 1976).
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Geotech Geol Eng
The hydraulic gradient, as described by the traditional Darcy’s law, is al
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