DEM analyses of one-dimensional compression and collapse behaviour of unsaturated structural loess |
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| Institution: | 1. State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, China Academy of Sciences, Lanzhou 730000, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, PR China;2. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;3. Ecole des Ponts ParisTech, Laboratoire Navier/CERMES, 6 et 8 avenue Blaise Pascal, 77455 Marne La Vallée, France;1. Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China;2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China;3. Laboratoire Navier/Géotechnique, Ecole des Ponts ParisTech, Université Paris Est, France;4. Department of Geological Engineering, Chang''an University, Xi''an 710054, China;5. Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education, Chang''an University, Xi''an 710054, China |
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| Abstract: | Natural loess is a kind of under-consolidated and unsaturated loose granulates (silts) with its microstructure characterized with large voids and inter-particle cementation. This paper presents a distinct element method (DEM) to investigate its macro- and micro-mechanical behaviour (compression and collapse behaviour) under one-dimensional (1D) compression condition. A relationship between bond strength in DEM model and initial water content is used to develop a bond contact model for loess. Then, DEM structural loess samples are prepared by the multi-layer under-compaction method, and cemented with the bond contact model. The effect of water content and void ratio on compression and collapse behaviour of loess is numerically investigated by simulating 1D compression and wetting tests on the DEM material. The DEM results agree qualitatively with available experimental observations in literatures. The wetting-induced deformation is independent of the sequence of wetting and loading under 1D compression condition. The macroscopic yielding and collapse behaviours are associated with bond breakage on microscopic scale. Moreover, bonds break in one of the two failure types in the simulations, i.e. tensile failure and shear failure (compression-shear failure and tension-shear failure), with bonds broken firstly mainly due to tension followed by shear when the samples are compressed, while mainly due to shear when the samples are wetted under a certain pressure. In addition, the contact orientations and deviator fabrics of contacts under 1D compression and wetting were also investigated. |
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| Keywords: | Loess soil Distinct element method One-dimensional compression Bond breakage Coefficient of collapsibility |
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