Investigation into microscopic mechanisms of anisotropic saturated permeability of undisturbed Q 2 loess
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ORIGINAL ARTICLE
Investigation into microscopic mechanisms of anisotropic saturated permeability of undisturbed Q2 loess Panpan Xu1,2 · Qiying Zhang1,2 · Hui Qian1,2 · Kai Hou1,2 Received: 8 April 2020 / Accepted: 25 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The anisotropic permeability of loess is an important engineering property. To explore the microscopic mechanisms of anisotropic saturated permeability of undisturbed loess, a series of laboratory tests, including constant-head saturated permeability test, particle size analysis, and scanning electron microscope imaging, were carried out for twelve Q 2 loess samples. The results show that with increasing burial depth, the saturated permeability decreases. Increasing the hydraulic gradient leads to an increase in permeability without changing the anisotropy of permeability. The spatial variability of the vertical permeability is more obvious than that in the horizontal direction. In addition, the permeability is negatively correlated with the clay particle content, and the uniformity coefficient of the particles. The area of the pores is the dominant factor controlling the permeability, especially the extra-large pores. Moreover, the direction and morphology of pores also affect the permeability of undisturbed loess. These findings are helpful for better understanding the water infiltration process in undisturbed loess and for investigating the stability of loess slopes. Keywords Undisturbed Q2 loess · Anisotropy · Permeability · Microscopic mechanism · Spatial variability
Introduction Loess is an aeolian deposit that formed during the Quaternary period and is widely distributed throughout the world, occupying 10% of the world’s land surface (Costantini et al. 2018; Luo et al. 2018; Shao et al. 2018; Wang et al. 2019b). China has one of the most widespread deposits of loess in the world, covering approximately 6.8% of its territory, and the loess is mainly distributed in the northwest of the country (Derbyshire 2001; Derbyshire et al. 2000; Gao et al. 2018) (Fig. 1). However, about one-third of the geological disasters in China occur on the Loess Plateau (Wang et al. 2020), such as landslides and ground settlement. In particular, the loess landslide disasters caused by atmospheric precipitation and artificial irrigation have attracted the extensive attention of many researchers (Leng et al. 2018; Xu et al. 2012; Zhang * Hui Qian [email protected] 1
School of Water and Environment, Chang’an University, Xi’an 710054, Shaanxi, China
Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region of the Ministry of Education, Chang’an University, Xi’an 710054, Shaanxi, China
2
and Liu 2010; Zhuang et al. 2018). The stability failure of slopes is controlled by many factors, such as soil structure, shear strength, and the chemical composition of pore water (Anthony and Agunwamba 2018; Kassou et al. 2020; Li and Leao 2018; Liang et al. 2018). These factors are closely related to hydraulic conduct
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