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Accueil du site → Doctorat → Australie → 2020 → Experimental study on the hydro mechanical behaviour of compacted loess-role of soil microstructure

University of Newcastle (2020)

Experimental study on the hydro mechanical behaviour of compacted loess-role of soil microstructure

Ge, Miaomiao

Titre : Experimental study on the hydro mechanical behaviour of compacted loess-role of soil microstructure

Auteur : Ge, Miaomiao

Université de soutenance : University of Newcastle

Grade : Doctor of Philosophy (PhD) in Geotechnical Engineering 2020

Résumé partiel
Loess is a loosely cemented silty soil, transported and deposited by wind, and formed in semi- arid continental climates. Loess in the Chinese Loess Plateau is famous all over the world for its continuity and high development. Loess is treated as problematic soil due to its collapsibility upon wetting. The predominance of loess deposits in northern China, together with the rapid expansion of urban areas, has led to the widespread use of loess in several infrastructure projects, mainly as a filling material. The long-term settlement, differential settlement and stability of loess fill slopes are the most urgent problems for those loess fill projects. However, these problems are highly correlated to the behaviour of unsaturated compacted loess under complex environmental actions. Therefore, study the hydro-mechanical behaviour of compacted loess is the primary task that is required to solve those engineering problems. In addition, soil behaviour is highly related to microstructure. Investigating soil microstructure change upon hydraulic coupling loading will help to reveal the mechanism of soil behaviour. Based on this, a comprehensive laboratory study, including one-dimensional and isotropic compression tests under constant water content conditions, one-dimensional compression tests under suction control conditions and gas permeability tests were conducted on compacted loess with modified testing equipment. These tests were combined with qualitative (Scanning Electron Microscopy, SEM) and quantitative (Mercury Intrusion Porosimetry, MIP) microstructure observation techniques to give additional insights into compacted loess behaviour, including compression, collapse and gas permeability. The main innovative works in this study are as follows : A series of one-dimensional and isotropic compression tests under constant water content conditions were carried out on compacted loess with modified one-dimensional oedometer and stress-path triaxial apparatus. Effects of the initial microstructure, stress level and loading history on the compressibility, collapse and stiffness of compacted loess were studied. The evolution of microstructure upon compression and wetting was investigated via MIP test and SEM analysis. The preliminary mechanism of compression, collapse and creep of unsaturated loess were revealed from both macro- and micro perspectives. Using the axis translation technique, a series of suction control tests were conducted to investigate the compressibility and wetting collapse of compacted loess

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