- Title
- Experimental and numerical study of shear band propagation and the pre-failure behaviours of slope using transparent soil and discrete element method
- Creator
- Wei, Lanting
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Landslides can pose a significant threat to infrastructures and human activities. For a soil with softening behaviour, landslide is normally accompanied with shear band development along a potential slip surface; it reflects in the slope movement which can be monitored from the ground and used for failure-time forecasting. However, the movement-based forecasting method is predominantly estimated using field experience rather than a scientific knowledge of the shear band development. The need to mitigate losses from landslides raises questions about a proper understanding of shear band evolution and how it affects the pre-failure behaviour of slopes. This thesis aims to reveal the fundamental mechanism of landslide with a focus on shear band evolution. The aim of this study was achieved by a series of experimental studies using transparent soil technique and numerical simulations by discrete element method (DEM). This aim was achieved by the following three tasks: (1) a transparent soil technique is proposed, which allows the visualization of shear band inside slopes in the laboratory physical model tests; (2) the fundamental mechanism of landslides is experimentally and numerically disclosed under some commonly existed external and intrinsic factors, and the shear band evolution is revealed; (3) the deformation of landslides with different process of shear band evolution are investigated; as a result, the mechanism of the three-phase deformation that widely observed in the actual landslide events is explained. Little studies of shear band evolution were found using the laboratory physical model test because of the absence of an effective method for detecting a shear band inside natural soil that is opaque. In this thesis, a new type of transparent soil was developed that allows the observation of a shear band in the laboratory-scale model. The geotechnical properties of the proposed transparent soil have been tested, and the transparent soil has similar strength parameters and permeability to natural cohesive soil—particularly arenaceous soil. A new set of laboratory equipment was then designed for applying the proposed transparent soil in physical model tests of slope, and a post-analysis method (feature-tracking method) was applied to track the development of the shear band. A slope model test confirmed the successful implementation of this new transparent soil and proved its compatibility with image-based methods to simulate the shear band evolution in slopes. By applying the transparent soil technique in physical model tests, shear band evolution is clearly visualised inside slopes. Parameter tests were taken in slopes considering the intrinsic factors (e.g., the slope geometry, the existence of a pre-existing weak plane, and the distribution of weak plane) and external factor (e.g., the location of surcharge). The influence of the slip surface evolution on the slope bearing capacity and slope movement were further investigated by physical model tests. A numerical model was established using DEM method to study the role of shear band evolution on the mechanical behaviours of slopes. Started with an accurate numerical representation of the particle shape, particle distribution and mechanical properties of the transparent soil, a discrete element formulation for modelling the proposed transparent soil was presented. In particular, the relationship between the micro parameters and the macro response was quantitatively established by the response surface method, then the micro parameters of the numerical model were calibrated to match the mechanical behaviour of the transparent soil. By using the DEM model, all patterns of shear band evolution in physical model tests were successfully reproduced, and a quantitative comparison between the simulated results and the existing experimental data was conducted. The numerical model was used for analysing the mechanical behaviour of slopes with different shear band evolution, with an emphasis on the slope movement, stress distribution, energy consumption, void ratio and particle connection. Finally, the numerical model was extended to simulate the shear band evolution and slope movement in large-scale landslides. The shear band evolution was presented in slopes with pre-existing short scarps (represents tension crack and transverse crack in the slope body), discontinuous flaws and long weak planes (represents bedding plane and fault). As a result, some widely observed failure modes of landslide (e.g. the retrogressive failure, key-block failure, glide slide and slump slide) were reproduced; accordingly, the actual landslide events were analysed in some detail. The classic three-phase movement, which is a general phenomenon observed in the real world, has been analysed with shear band evolution.
- Subject
- landslide; shear band; transparent soil; slope movement; discrete element method
- Identifier
- http://hdl.handle.net/1959.13/1504718
- Identifier
- uon:55566
- Rights
- Copyright 2022 Lanting Wei
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT01 | Thesis | 15 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 376 KB | Adobe Acrobat PDF | View Details Download |