ORCID Profile
0000-0001-6078-2559
Current Organisation
University of Technology Sydney
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Civil Engineering | Civil engineering | Civil Geotechnical Engineering | Civil geotechnical engineering |
Rail Infrastructure and Networks | Civil Construction Design
Publisher: MDPI AG
Date: 25-05-2023
DOI: 10.3390/SU15118603
Abstract: Enhancing the use of natural fibre for geotechnical purposes has attracted greater attention in the past decade, mainly because of the tangible benefits that this green approach would bring to our sustainable infrastructure developments. While this topic has been subjected to often sceptical review or discussions, they usually focus on narrow aspects such as soil reinforcement, resulting in a lack of thorough assessment over different aspects and applications. The current paper hence aims to not only provide a more balanced review between theoretical concepts and practical perspectives, but also to link different functions of natural fibre that would facilitate design effectiveness. Three major geotechnical purposes of natural fibre in terms of the practice are identified and discussed, i.e., (i) soil reinforcement (ii) enhanced drainage for soil consolidation and (iii) filtration, separation and erosion controls. In these distinct applications, natural fibres, despite being used in different forms such as geotextiles, drains and in idual fibres, often give significant contributions to improving soil structures, resulting in greater stabilization of the entire system. The key unique feature of natural fibres is their ability to generate biological bonding with soil media (i.e., biodegradation associated with reinforcement), while substantially improving the tensile strength of the soil structure, thus providing larger resistance to mud pumping, liquefaction, internal instability and erosion. Apart from successful findings and applications in practice, main challenges that are currently h ering the wider application of natural fibres will be addressed in this paper.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Springer Science and Business Media LLC
Date: 28-10-2023
DOI: 10.1007/S11440-022-01679-2
Abstract: The nonlinear variation of soil compressibility and permeability with void ratio (i.e., e -log σ ′ and e -log k ) has been included in the consolidation theory to accurately predict the behavior of soft soil stabilized by vertical drains. However, most current nonlinear consolidation models incorporating the coupled radial-vertical flow are based on some simplified assumptions, while including some features such as the complex implementation of multilayered computations, time-dependent loading and stress distribution with depth. This study hence introduces a novel approach where the spectral method is used to analyze the nonlinear consolidation behavior of multilayered soil associated with coupled vertical-radial drainage. In addition, time- and depth-dependent stress and soil properties at each soil layer are incorporated into the proposed model. Subsequently, the solution is verified against experimental and field data with comparison to previous analytical solutions. The results show greater accuracy of the proposed method in predicting in-situ soil behavior. A parametric study based on the proposed solution indicates that the ratio between the compression and permeability indices ( ω = C c /C k ) has a great impact on the consolidation rate, i.e., the greater the ω , the smaller the consolidation rate. Increasing the load increment ratio and the absolute difference between unity and ω (i.e., | ω − 1|) can exacerbate prediction error if the conventional simplified methods are used.
Publisher: Springer Science and Business Media LLC
Date: 14-02-2022
DOI: 10.1007/S11440-022-01477-W
Abstract: The influence of stress anisotropy ( K ) (i.e. the ratio between effective horizontal and vertical stresses) on the shear behaviour of soils has received significant attention in past studies, but how its influence depends on different values of the plasticity index (PI) has not been properly quantified. In this study, the results of a series of undrained triaxial tests on anisotropically consolidated soil at different values of K are reported , and together with past experimental data, the interactive roles of K and PI on the shear behaviour of soil are rigorously interpreted. The findings indicate that the peak shear strength increases with higher brittleness, whereas the peak excess pore pressure diminishes when the value of K decreases. Moreover, increasing the value of PI up to 35 tends to increase the peak shear strength, but beyond that the influence of PI seems marginal. Based on the findings of this study, empirical equations incorporating PI and K to estimate the undrained shear strength are proposed with acceptable accuracy.
Publisher: American Society of Civil Engineers (ASCE)
Date: 06-2018
Publisher: Springer Singapore
Date: 2019
Publisher: Canadian Science Publishing
Date: 2017
Abstract: Over many decades, natural fibre bundles have been widely used for drainage and filtration applications because of their favourable hydraulic conductivity and abundance in Asian countries. In recent times, natural (biodegradable) coir and jute drains, which are environmentally friendly, have been considered in lieu of conventional geosynthetic wick drains for soft clay consolidation in Australian coastal regions. However, there is a lack of a computational framework to predict the hydraulic behaviour of fibre drains on the basis of micromechanical (fabric) characteristics. Employing computational fluid dynamics (CFD) coupled with the discrete element method (DEM) to model the hydraulic behaviour of fibrous materials has shown promise in an earlier 2016 study by Nguyen and Indraratna, which considered an idealized parallel arrangement of fibres for simplicity. This paper aims to broaden the application of the coupled CFD–DEM technique to real fibres (coconut coir) considering both nontwisted and twisted fibre bundles that have more complex porous structure. The hydraulic conductivity determined from the numerical approach is validated with the experimental results, and also compared with the analytical prediction based on the conventional Kozeny–Carmen (KC) approach. The current study shows that the CFD–DEM technique can capture well the fluid flow characteristics of a nonuniform fibrous structure, including dense twisted coir bundles.
Publisher: Springer Science and Business Media LLC
Date: 08-11-2022
DOI: 10.1007/S11440-022-01736-W
Abstract: This study aims to examine the performance of artificial neural network (ANN) model based on 1137 datasets of super-large (1.0–2.5 m in equivalent diameter) and long (40.2–99 m) piles collected over 37 real projects in the past 10 years in Mekong Delta. Five key input parameters including the load, the displacement, the Standard Penetration Test value of the base soil, the distance between the loading point and pile toe, and the axial stiffness are identified via assessing the results of field load tests. Key innovations of this study are (i) use of large database to evaluate the effect that random selection of training and testing datasets can have on the predicted outcomes of ANN modelling, (ii) a simple approach using multiple learning rates to enhance training process, (iii) clarification of the role that the selected input factors can play in the base resistance, and (iv) new empirical relationships between the pile load and settlement. The results show that the random selection of training and testing datasets can affect significantly the predicted results, for ex le, the confidence of prediction can drop under 80% when an average R 2 0.85 is required. The analysis indicates predominant role of the displacement in governing the base resistance of piles, providing significant implication to practical designs.
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2021
Publisher: Elsevier BV
Date: 03-2020
Publisher: Canadian Science Publishing
Date: 07-2016
Abstract: Modelling fluid flow through fibrous porous materials has gained increasing attention from industry and research communities. Analytical and numerical methods are commonly used to predict the hydraulic characteristics of fibrous material during fluid flow, although to date most techniques have been conducted using the same assumption that the geometric features of fibres remain unchanged. In other words, the mutual interaction between fibre elements and fluid is ignored, which undermines the actual working condition of fibres. This paper therefore presents a potential numerical approach that is capable of capturing the behaviour of a fluid–solid system. In idual fibres are simulated by the discrete element method (DEM) coupled with the concept of computational fluid dynamics (CFD), whereby the information contained in each phase is constantly exchanged and updated with other phases. In comparison with conventional solutions, including the Kozeny–Carman (K–C) fluid flow principle and other valid studies, the results show an acceptable agreement in predicting the hydraulic conductivity of a fibrous system. Subjected to laminar longitudinal flow, fibre motion is also evaluated with respect to varying bond stiffness and flow velocity. The study indicates the potential of the proposed technique in modelling drainage and filtration that is based on the hydraulic behaviour of fibrous porous geomaterials.
Publisher: Thomas Telford Ltd.
Date: 12-2018
Abstract: Because of their distinct features such as biodegradability and favourable engineering properties, naturally occurring materials including jute and coconut fibres have been used increasingly in numerous geoengineering applications in recent years. However, these materials can sometimes decompose rapidly when subjected to adverse environmental conditions, resulting in severe degradation of their engineering characteristics and consequently causing damage to the design target. This paper presents a numerical approach where the finite-element method (FEM) is used to estimate the influence that the degradation of natural fibre drains can have on soil consolidation. A subroutine which can describe the reduction in drain discharge capacity over time is incorporated into the FEM model. Different cases including those varying the rate and time-dependent form of biodegradation are examined in this paper. The results of this investigation indicate that the dissipation of excess pore pressure can be h ered significantly if drains decay too early and speedily, particularly when the discharge capacity falls below 0·03 m 3 /d. Different rates of decay can impose different consolidation responses in the surrounding soft soil. Application of the proposed FEM to compare with laboratory data indicates an acceptable agreement between the predictions and the measurements.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Springer Science and Business Media LLC
Date: 28-05-2020
DOI: 10.1007/S40534-020-00210-1
Abstract: The rapid growth in railway infrastructure and the construction of high-speed heavy-haul rail network, especially on ground that is basically unsuitable, poses challenges for geotechnical engineers because a large part of the money invested in the development of railway lines is often spent on track maintenance. In fact around the world, the mud pumping of subgrade fines is one of the common reasons why track performance deteriorates and track stability is hindered. This article presents a series of laboratory tests to examine following aspects of mud pumping: (1) the mechanisms of subgrade fluidisation under undrained condition, (2) the effects of mud pumping on the engineering characteristics of ballast, and (3) the use of vertical drains to stabilize subgrade under cyclic loads. The undrained cyclic triaxial testing on vulnerable soft subgrade was performed by varying the cyclic stress ratio (CSR) from 0.2 to 1.0 and the loading frequency f from 1.0 to 5.0 Hz. It is seen from the test results that for a specimen compacted at an initial dry density of 1790 kg/m 3 , the top portion of the specimen fluidises at CSR = 0.5, irrespective of the applied loading frequency. Under cyclic railway loading, the internal redistribution of water at the top of the subgrade layer softens the soil and also reduces its stiffness. In response to these problems, this paper explains how the inclusion of vertical drains in soft subgrade will help to prevent mud pumping by alleviating the build-up of excess pore pressures under moving train loads.
Publisher: Elsevier BV
Date: 09-2016
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 07-2021
Publisher: Springer International Publishing
Date: 2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2019
Publisher: Canadian Science Publishing
Date: 11-2020
Abstract: A long-term issue that has h ered the efficient operation of heavy-haul tracks is the migration of fluidized fines from the shallow soft subgrade to the overlying ballast, i.e., mud pumping. This paper presents a series of undrained cyclic triaxial tests where realistic cyclic loading conditions were simulated at low confining pressure that is typical of shallow subgrade beneath a ballast track. Subgrade soil specimens with a low-plasticity index collected from a field site with recent history of mud pumping were tested at frequencies from 1.0 to 5.0 Hz and a cyclic stress ratio (CSR) from 0.1 to 1.0. The experimental results indicate that under adverse loading conditions of critical cyclic stress ratio (CSR c ) and frequency, there is upward migration of moisture and the finest particles towards the specimen top and this causes the uppermost part of the soil specimen to soften and fluidize. Conversely, a smaller value of CSR tends to maintain stability of the specimen despite the increasing number of loading cycles. It is noteworthy that for any given combination of CSR and frequency, the relative compaction has a significant influence on the cyclic behaviour of the soil and its potential for fluidization.
Publisher: Informa UK Limited
Date: 02-02-2021
Publisher: Thomas Telford Ltd.
Date: 08-2017
Abstract: Natural fibres such as jute and coir are emerging as distinct alternatives to synthetic geomaterials, and in recent years they have been used increasingly for drainage and filtration in field applications. However, these naturally occurring materials are extremely variable in micro-characteristics such as the size, uniformity and shape of their fibres, while there is a lack of studies addressing how these differences can affect the hydraulic behaviour of fibrous media. This paper offers a laboratory study of the influence of micro-features on the hydraulic conductivity of fibre drain. Non-twisted and twisted fibre drains made from jute and coir were subjected to hydraulic conductivity testing and micro-analyses. Experimental results show a considerable contribution of the size characteristics of fibre to the hydraulic behaviour of the drain. A less-rounded shape of fibre and a larger twisting angle of the drain can increase the fluid–fibre contact area and the corresponding tortuosity of flow, which significantly reduces the drain permeability. The way in which the Kozeny–Carmen analytical approach can be adopted to predict the permeability of a fibre drain is discussed based on the experimental results, considering various micro-factors including the size of fibre, uniformity and the associated porosity.
Publisher: MDPI AG
Date: 02-08-2023
DOI: 10.3390/SU151511884
Abstract: Sustainable construction has become increasingly crucial recently due to the massive negative impacts that construction, including various geotechnical activities, can have on the surrounding environment [...]
Start Date: 2021
End Date: 2022
Funder: University of Technology Sydney
View Funded ActivityStart Date: 2017
End Date: 2022
Funder: Australian Research Council
View Funded ActivityStart Date: 03-2023
End Date: 03-2026
Amount: $443,181.00
Funder: Australian Research Council
View Funded ActivityStart Date: 08-2017
End Date: 07-2022
Amount: $675,000.00
Funder: Australian Research Council
View Funded Activity