Wetting-Induced Collapse Behavior of Unsaturated and Structural Loess under Biaxial Tests Using Distinct Element Method
Publication: International Journal of Geomechanics
Volume 17, Issue 1
Abstract
Loess soils undergo collapse when the material is loaded and wetted, which leads to engineering problems and disasters. To understand better the collapse mechanisms that govern loess and loess-like deposits under complex stress paths, a distinct element model has been established. A contact model considering water content effect introduced for structural loess was used to cement contacted particles together to simulate unsaturated structural loess under biaxial compression conditions. The numerical structural loess was tested for different wetting and loading paths, i.e., loading-quick wetting (LWQ), loading-gradual wetting (LWG), and wetting-loading (WL) paths. The simulated macroscopic mechanical behavior agrees approximately quantitatively in terms of the deviatoric deformation and qualitatively regarding the volumetric deformation when compared with available experimental results. The tests under different mean stresses indicate the existence of initial, maximum, and terminating collapse stress states in a biaxial wetting test. The influence of the wetting procedure, i.e., gradual wetting or quick wetting, has a considerable effect on the mechanical performance for numerical samples. The axial strain of a sample during a loading-wetting (LW) path is larger than that of a sample in a WL path. The wetting-induced volumetric deformation corresponds with the failure of bonded contacts. The deviator fabrics (fabric anisotropy) of total, bonded, frictional, and broken bond contacts were also investigated.
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Acknowledgments
This work was funded by National Basic Research Program of China (Grants 2011CB013504 and 2014CB046901), China National Natural Science Foundation (Grant 51579178), the 111 project (Grant B14017), and State Key Laboratory of Disaster Reduction in Civil Engineering (Grant SLDRCE14-A-04). This support is greatly appreciated.
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Published In
International Journal of Geomechanics
Volume 17 • Issue 1 • January 2017
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Nov 4, 2014
Accepted: Mar 15, 2016
Published online: Apr 4, 2016
Discussion open until: Sep 4, 2016
Published in print: Jan 1, 2017
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