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Title: Numerical modelling of unsaturated tropical slopes
Authors: Mohd Taib, Aizat Bin
Issue Date: 2018
Publisher: Newcastle University
Abstract: Adapting to climate change is one of the greatest challenges facing engineers. Many studies have been conducted since the 1900s directed at predicting extreme weather events. Changes in global weather patterns, such as temperature and rainfall distributions, can have major economic and societal impacts. One example, addressed in this thesis, is the stability of natural slopes. In Southeast Asia, landslides are common due to the effect of abundant rainfall during the wet monsoon. The local climate in the region is characterised by annual wet and dry seasons, in which the cycle forms an unsaturated zone at the surface of the slopes. However, as a result of climate change, prolonged drying and heavy rainfall are observed that may exacerbate slope failure particularly in unsaturated soils. The prediction and mitigation of slope failures are consequently major challenges due to the complexity of the unsaturated behaviour of tropical soils subjected to irregular weather changes. This thesis develops a methodology to model unsaturated slope behaviour taking into account the effects of climate change. The approach includes groundwater flow, soil deformation and stability analyses using a finite element method and climate change predictions to incorporate future weather scenarios. The method was established by validating the groundwater flow analysis by involving a case study in Zaoyang, China. Subsequently, a more complex case study of a tropical unsaturated slope in Bukit Timah, Singapore was also considered to calibrate the soil-water characteristic curves (SWCC), a major controlling factor in unsaturated soils mechanics. The coupled flow-deformation analysis was undertaken on the validated case studies to predict soil displacement. In addition, a parametric study was conducted to critically analyse the effects of void ratio, saturated permeability, hysteretic SWCC, soil elasticity and rainfall intensity regarding slope behaviour. Finally, statistical analysis was performed to predict the impact of climate change on the rainfall distribution in Singapore up to the year 2100 by using the historical data from 1980 to 2010. Frequency analysis was adopted to estimate the rainfall return period. The results of the future extreme rainfall were compared to predictions by the Met Office in Singapore and the United Kingdom. The effects of climate change on slope behaviour was assessed by applying the predicted climate in the slope models. The outcomes reveal that the modelling approach is able to capture groundwater flow, slope deformation and safety factor accurately under extreme weather scenarios.
Description: PhD Thesis
Appears in Collections:School of Engineering

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