Journal
CATENA
Volume 173, Issue -, Pages 276-288Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.catena.2018.10.006
Keywords
Microstructure; SEM; Morphology properties; Image processing; Collapse; Shear strength
Funding
- Ministry of Science and Technology of China [2017YFD0800501]
- National Natural Science Foundation of China [41772323]
- Science and Technology Department of Shaanxi Provincial Government [2016KW-030]
- State Key Laboratory of Continental Dynamics [BJ14268]
- Education Department of Shaanxi Provincial Government [18JK0785]
- Key Laboratory for Geo-hazard in Loess Area [KLGLAMLR201502]
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A series of laboratory tests were conducted on intact specimens of two loess soils to characterize their collapsibility, shear strength, microstructure and mineralogy. In addition, microstructural observations were performed on the specimens after various mechanical tests (odometer-collapse tests and triaxial tests). The micrographs were processed using MATLAB program and the morphology properties of soil pores (including area, major axis length, eccentricity and orientation) were obtained. The micrographs and variations in distributions of the pore morphology properties were used to interpret the microstructural evolution of loess soils due to loading and wetting. Results of the study highlight that collapsible loess soils have an open structure, where clay coated silts and clay-silt aggregates functioning as fundamental units are connected to each other with a few cementations. Upon loading and wetting, disintegration of clay aggregates (cementations), breakdown of carbonate cementations and other bonding agents initiate the failure of soil structure. This is followed by particle movement and rearrangement, transforming the initial open structure into a closer one. The microstructural evolution is dependent on the stress level and stress path. With the increase in stress level, large-sized inter aggregate pores transform into small-sized infra-aggregate pores; the pores are flatter and still randomly orientated. Fissures with the size and connectivity related to the stress level may develop in the specimen under a triaxial stress state, depending on the stress path.
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