Experimental study on air permeability and microscopic mechanism of intact and remolded Malan loess, Loess Plateau, Chin
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REVIEW PAPER
Experimental study on air permeability and microscopic mechanism of intact and remolded Malan loess, Loess Plateau, China Jinyang Liu 1,2 & Xi’an Li 2 & Quan Xue 2 & Zeze Guo 2 Received: 14 July 2019 / Accepted: 17 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract As a natural foundation and fill material for construction in loess areas, there exists a significant impact on the stability of the engineering construction due to the permeation characteristics of the eolic sediment Malan loess. In this study, a series of air permeability tests were conducted for intact loess and remolded loess by using an improved air permeameter. We determined the influence of the water content, wetting and drying, dry density on the air permeability ka, and the use of microstructure models, scanning electron microscope (SEM) micrographs, and 3D super depth of field microscope micrographs to elucidate the microscopic mechanism of the air permeation. The results show that the air permeability ka of the remolded loess increased with the initial water content of remolding loess at dry density of ρd ≦ 1.6 g/cm3 increase, which is because of the formation of aggregates, and menisci water effect in loess; however, at dry density of ρd > 1.6 g/cm3, the air permeability started to decrease. The ka reduced remarkably as the water content of the intact and remolded loess increased during wetting process, and the air permeability during the drying process was always higher than the air permeability in the wetting process at the same water content. With the increase in the dry density, the air permeability of the remolded loess decreased; from a microstructural perspective, large and round pores tend to be small and elongated and irregular pores at high dry density. This paper will contribute to elucidating air permeability characteristics of loess and reducing the permeation risk in stability of the engineering construction in the Loess Plateau. Keywords Air permeability . Water content . Wetting and drying . Pore structure . Eolic sediment
Introduction At present, the single-ring method and double-ring method are commonly used to measure the hydraulic conductivity Kw of soils in situ, and the water permeameter is used in the * Xi’an Li [email protected] Jinyang Liu [email protected] Quan Xue [email protected] Zeze Guo [email protected] 1
School of Civil Engineering, Chongqing University, Chongqing 400045, China
2
School of Geological Engineering and Geomatics, Chang’an University, Xi’an 710054, Shaanxi, China
laboratory infiltration tests, but these methods often cannot meet actual engineering requirements because they consume time and effort; therefore, some researchers use the air permeability ka to replace hydraulic conductivity Kw (Neyshaboury et al. 2015) (Chief et al. 2008). The air permeability ka is a basic physical index used to measure the permeability of porous media. It can characterize the ability of air passing through the porous material under a pressure gradient and also indicate
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