ORCID Profile
0000-0002-0638-4055
Current Organisation
University of South Australia: Adelaide, South Australia, AU
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Civil Engineering | Civil Geotechnical Engineering
Management of Solid Waste from Mineral Resource Activities |
Publisher: Elsevier BV
Date: 09-2013
Publisher: Elsevier BV
Date: 12-2021
Publisher: MDPI AG
Date: 10-11-2022
DOI: 10.3390/SU142214852
Abstract: The reuse of end-of-life (EOL) tyres as earth reinforcement materials in civil engineering projects have been studied for decades. Entire EOL tyres infilled with compacted soil can form segmental tyre encased soil elements (TESEs) with considerable load-bearing capacity. The TESEs can be used to construct structures like low-rise buildings, railway foundations and geotechnical structures. One of the most important aspects of TESE systems, i.e., the shearing interaction between neighbouring units is not yet well understood. In this study, thirty-six laboratory tests have been conducted to investigate the response of TESEs under intercourse shear actions. This was followed by a supply chain environment and economic analysis to investigate the acceptability of the system. The results revealed that the type of encased soil had more effect on the interface interactions between courses of TESEs compared to the TESEs’ construction pattern. It was also found that the frictional coefficient could be increased by either using coarse and angular aggregates as the encased soil or reducing the amount of the encased soil to form a high portion of rubber-to-rubber contact at the composite interface. Supply chain environment and economic analysis revealed that using entire tyres as construction materials has low CO2 emission and considerable economic benefits.
Publisher: American Society of Civil Engineers
Date: 23-03-2023
Publisher: American Society of Civil Engineers
Date: 17-03-2015
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2015
Publisher: Springer Science and Business Media LLC
Date: 11-08-2021
Publisher: Thomas Telford Ltd.
Date: 25-09-2023
Abstract: Urease enzymes from plants are directly utilised in enzyme induced calcite precipitation (EICP) to catalyse calcium carbonate (CaCO 3 ) precipitation between soil particles to improve their strength and stiffness. EICP does not require microbial culture and may be applicable for finer soils due to their smaller size. However, most studies on EICP utilise purified urease enzymes, which are often rare, expensive and limited to food-grade beans or seeds, making the technique less cost-effective. To find alternative and cheaper sources, crude urease extracts from erse plant species, particularly weeds and Australian native plants, were obtained, identified and characterised using a series of in vitro experiments. All selected plant species contain a considerable amount of urease enzyme, exhibiting different urease activity and CaCO 3 precipitation. EICP treatment by different crude extracts showed different levels of hydraulic conductivity, unconfined compressive strength (UCS), wind and raindrop erosion resistance. However, the crude extract from an Australian weed, matured Paddy melon seeds (M-PMS), had the highest specific activity of 8997U/mg and was further used for EICP treatment of six different soil types. The UCS of treated soils was influenced by the soil types. For similar CaCO 3 content, the strength and stiffness of the EICP-treated specimens were significantly influenced by the confining stress and degree of saturation in undrained triaxial conditions. Also, the mass loss, strength and average CaCO 3 decreased with increasing cycles of wetting-drying, freezing-thawing and elevated temperature. When compared with purified urease enzyme, M-PMS produced comparable strength and durability resistance for the treated s les.
Publisher: American Society of Civil Engineers
Date: 21-03-2019
Publisher: Elsevier BV
Date: 02-2023
DOI: 10.1016/J.JHAZMAT.2022.130417
Abstract: Biomineralization as an alternative to traditional remediation measures has been widely applied to remediate copper (Cu)-contaminated sites due to its environmental-friendly nature. Immobilizing Cu is, however, a challenging task as it inevitably causes inactivation of ureolytic bacteria. In the present work, a series of test tube experiments were conducted to derive the relationships of Cu immobilization efficiency versus pH conditions. The Cu speciation transformation that is invisible in the test tube experiments was investigated via numerical simulations. Apart from that, the one-dimensional soil column tests, accompanied by the X-ray diffraction (XRD) and Raman spectroscopy analysis, mainly aimed not only to investigate the variations of Cu immobilization efficiency with the depth but to reveal the underlying mechanisms affecting the Cu immobilization efficiency. The results of the test tube experiments highlight the necessity of narrowing pH ranges to as close as 7 by introducing an appropriate bacterial inoculation proportion. The coordination adsorption of Cu, while performing the one-dimensional soil column tests, is encouraged by alkaline environments, which differs from the test tube experiments where Cu
Publisher: Springer Singapore
Date: 2020
Publisher: American Society of Civil Engineers
Date: 29-03-2012
Publisher: Thomas Telford Ltd.
Date: 02-2017
Abstract: The behaviour of granular material was investigated by simulating an undrained triaxial compression test for three-dimensional assembly of ellipsoid particles over a wide range of void ratio, e, and mean confining stress, p′. The assembly was either isotropically consolidated or K 0 consolidated prior to undrained shearing up to 30% axial strain to reach steady-state conditions. A unique steady-state line was obtained, irrespective of the consolidation path. The micro-mechanical quantities, such as coordination number and von Mises fabric in terms of second invariant of deviatoric fabric, F vM , also reached steady-state values. The normalised anisotropic fabric variable, A, and the trace of the joint stress–fabric tensor, K F , evolved during undrained simulation and reached the steady-state value at the end of shearing. This forms a unique relationship in K F –p′–e space and the projection of this relationship in e–log(p′) space is the classical steady-state line. This underpins the concept of fabric evolution and steady-state fabric in anisotropic critical state theory. The relationships of state parameter, ψ, and stress ratio at instability, η IS = (q ′) IS , were dependent on consolidation path, and the difference was not related to coordination number, but to F vM . However, a new phenomenon was observed that stress ratio, η, at the end of K 0 consolidation and η IS may reach beyond the steady-state stress ratio, M. Experimental data are needed to verify this until then such behaviour should be regarded as unproven.
Publisher: CRC Press
Date: 10-05-2021
Publisher: Springer Science and Business Media LLC
Date: 03-12-2022
Publisher: Canadian Science Publishing
Date: 04-2009
DOI: 10.1139/T09-025
Publisher: American Society of Civil Engineers (ASCE)
Date: 2018
Publisher: MDPI AG
Date: 17-10-2021
DOI: 10.3390/EN14206760
Abstract: Expansive soils go through significant volume changes due to seasonal moisture variations resulting in ground movements. The ground movement related problems are likely to worsen in the future due to climate change. It is important to understand and incorporate likely future changes in design to ensure the resilience of structures built on such soils. However, there has been a limited amount of work quantifying the effect of climate change on expansive soils movement and related behaviour of structures. The Thornthwaite Moisture Index (TMI) is one of the commonly used climate classifiers in quantifying the effect of atmospheric boundary on soil behaviour. Using the long-term weather data and predicted future changes under different emission scenarios, a series of TMI maps are developed for South Australia. Potential changes in ground movement are then estimated for a selected area using a simplified methodology where the effect of future climate is captured through changes in TMI. Results indicate that South Australia is likely to face a significant reduction in TMI under all emission scenarios considered in this study. The changes in TMI will lead to a considerable increase in potential ground movement which will influence the behaviour of structures built on them and in some areas may lead to premature failure if not considered in the design.
Publisher: Springer Singapore
Date: 2021
Publisher: Springer Singapore
Date: 04-09-2020
Publisher: Elsevier BV
Date: 10-2019
Publisher: MDPI AG
Date: 24-11-2022
DOI: 10.3390/SU142315662
Abstract: Lightweight structures built on expansive soils are susceptible to damage caused by soil movement. Financial losses resulting from the improper design of structures on expansive soils can be significant. The interactions and failure mechanisms of different geotechnical structures constructed on such soils differ depending on the structure type, site characteristics, and climatic conditions, as the behaviour of expansive soils is influenced by moisture variations. Therefore, the performance of different geotechnical structures (e.g., lightweight footings for residential buildings) is expected to be adversely affected by climate change (especially rainfall and temperature change), as geotechnical structures are often designed to have a service life of 50–100 years. Some structures may even fail if the effect of climate change is not considered in the present design. This review aims to provide insights into problems associated with expansive soils that trigger the failure of lightweight structures, including current investigations and industry practices. This review recognises that although the soil moisture conditions govern expansive soil behaviour, limited studies have incorporated the effect of future climate changes. In addition, this review identifies the need to improve the current Australian design practice for residential footings through the inclusion of more site-specific investigations and expected climate changes.
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2017
Publisher: SAE International
Date: 11-04-2023
DOI: 10.4271/2023-01-0890
Abstract: class="section abstract" class="htmlview paragraph" Because of the negative impacts of pollutions on us and our surroundings, it is important to measure the magnitude of emissions in metropolitan areas where the emission concentrations are highest. The Mesoscale approach was used for probabilistic emission inventory. The traffic volume data for each road link were required and collected from the Victoria state road traffic authority for further calculation for different Euro standards in different vehicle categories. The pollutants studied in this paper are nitrogen oxides (NO sub X /sub ), carbon monoxide (CO), and particulate matter (PM), as transportation-induced emissions constitute the principal source of city pollution. This paper examined the deterministic modelling and stochastic modelling approaches for estimating on-road emissions. The Monte Carlo simulation approach was applied for stochastic modelling. Estimated emissions were calculated using a deterministic approach for various road links, which were 79,000 g/km Carbon Monoxide (CO) for light private vehicles for a particular road link, but when the emissions for the same link were calculated using stochastic modelling, the emission estimated were around 82,000 g/km Carbon Monoxide (CO). This paper also analyzed different scenarios and future scenarios. When a 21% growth (in the year 2030) in vehicle registration is expected, considering the current growth trend, a 17% increase in CO emission is estimated in all vehicle categories. Different scenarios were analyzed assuming 50% of euro 3 vehicles were replaced by euro 5 (by the year 2020), then there would be a 34% reduction in CO emission for the same road link, which is 31,191 g/km less. / /
Publisher: Elsevier BV
Date: 11-2021
Publisher: American Society of Civil Engineers
Date: 17-03-2015
Publisher: Frontiers Media SA
Date: 27-03-2023
DOI: 10.3389/FBIOE.2023.1146858
Abstract: Inappropriate irrigation could trigger migration of heavy metals into surrounding environments, causing their accumulation and a serious threat to human central nervous system. Traditional site remediation technologies are criticized because they are time-consuming and featured with high risk of secondary pollution. In the past few years, the microbial-induced carbonate precipitation (MICP) is considered as an alternative to traditional technologies due to its easy maneuverability. The enzyme-induced carbonate precipitate (EICP) has attracted attention because bacterial cultivation is not required prior to catalyzing urea hydrolysis. This study compared the performance of lead (Pb) and copper (Cu) remediation using MICP and EICP respectively. The effect of the degree of urea hydrolysis, mass and species of carbonate precipitation, and chemical and thermodynamic properties of carbonates on the remediation efficiency was investigated. Results indicated that ammonium ion (NH 4 + ) concentration reduced with the increase in lead ion (Pb 2+ ) or copper ion (Cu 2+ ) concentration, and for a given Pb 2+ or Cu 2+ concentration, it was much higher under MICP than EICP. Further, the remediation efficiency against Cu 2+ is approximately zero, which is way below that against Pb 2+ (approximately 100%). The Cu 2+ toxicity denatured and even inactivated the urease, reducing the degree of urea hydrolysis and the remediation efficiency. Moreover, the reduction in the remediation efficiency against Pb 2+ and Cu 2+ appeared to be due to the precipitations of cotunnite and atacamite respectively. Their chemical and thermodynamic properties were not as good as calcite, cerussite, phosgenite, and malachite. The findings shed light on the underlying mechanism affecting the remediation efficiency against Pb 2+ and Cu 2+ .
Publisher: Elsevier BV
Date: 06-2014
Publisher: Thomas Telford Ltd.
Date: 03-2021
Publisher: MDPI AG
Date: 30-05-2021
DOI: 10.3390/JCS5060146
Abstract: Different types of recycled plastic have been used in concrete and most studies have focused on the behaviour of a single type of plastic. However, separating plastic wastes increases the cost and time of processing. To tackle this problem, this research presents an experimental investigation to determine the effect of incorporating different combinations of three types of recycled plastic waste aggregates—Polyethylene terephthalate (PET), High Density Polyethylene (HDPE) and Polypropylene (PP)—at different replacement ratios of coarse aggregate on physical and mechanical properties of concrete. The combinations include two plastic types at 10% and 20% replacement ratios and three plastic types at 15% and 30% replacement ratios. The performance of the plastic concrete was assessed based on various physical and mechanical properties including workability, fresh and dry densities, air content, compressive, indirect tensile and flexural strengths, modulus of elasticity, stress-strain behaviour and ultrasonic pulse velocity. It is found that the workability of Mixed Recycled Plastic Concrete (MRPC) at a low replacement rate is independent of the type of plastic. The minimum reduction in the compressive strength, indirect tensile and modulus of elasticity were achieved by R3 (PET + PP) at 10% replacement, while R5 (HDPE + PP) at 10% replacement achieved the highest flexural strength and ultrasonic pulse velocity values. The findings suggest that the mixed recycled plastics have a good possibility to partially replace coarse aggregates in concrete which will benefit the plastics recycling community and environment. Furthermore, the study will provide guidance to the concrete industry concerning the effect of the implementation of unsorted mixed types of plastic as coarse aggregates in the production of concrete.
Publisher: American Society of Civil Engineers
Date: 11-03-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2023
Publisher: Elsevier BV
Date: 08-2021
Publisher: Thomas Telford Ltd.
Date: 10-2018
Publisher: Springer International Publishing
Date: 29-10-2019
Publisher: MDPI AG
Date: 15-11-2019
DOI: 10.3390/SU11226427
Abstract: Emissions modelling is an important tool for assessing the urban health status of any city, but often the assessments are affected by the uncertainty of the data used for the modelling. Therefore, a Monte Carlo simulation technique was used for a probabilistic emissions modelling of Dhaka City by simulating 20,000 scenarios for the highest and lowest values of traffic volume and speed profiles for each of the major road links. Only nitrogen oxide (NOx) emissions from on-road vehicles were considered, as vehicular sources are major contributors. Each dataset included two peak periods and an offpeak period of the day to cover the diurnal variation within each road link. Using the probability of the magnitude of emissions along with the corresponding health risk, a series of spatial urban health risk severity scenarios was generated for 2018 and 2024, suggesting that transportation and environmental planning is required for urban sustainability.
Publisher: CRC Press
Date: 04-09-2014
DOI: 10.1201/B17435-27
Publisher: Springer Science and Business Media LLC
Date: 15-08-2021
Publisher: MDPI AG
Date: 25-05-2020
DOI: 10.3390/SU12104313
Abstract: The mechanistic design of a concrete block pavement (CBP) can be very complicated and often requires the use of computer programs. This paper presents a new mechanistic-empirical method, which is implemented in a computer program (DesignPave) that calculates base course/sub-base thicknesses for a range of design inputs such as traffic load, interlocking properties, and material stiffness. A range of virgin and recycled unbound granular materials were also experimentally tested to characterize them for possible use as base course or sub-base materials. Combining the new mechanistic-empirical method and the range of base course/sub-base course materials (virgin and recycled aggregates), it was found that while a CBP containing recycled aggregates did not offer a significant direct financial benefit based on the characteristics or material costs, the associated environmental benefits were very high.
Publisher: American Society of Civil Engineers (ASCE)
Date: 2014
Publisher: MDPI AG
Date: 21-01-2022
DOI: 10.3390/SU14031230
Abstract: Kerb is an integral part of road infrastructure and performs several important functions, including providing stability to the edges of the road and providing effective drainage. Their performance can significantly influence the behaviour and service life of a road. The design conditions, construction materials and their sustainability can be important to assess from an asset management and sustainable construction point of view even though this area has been paid limited research attention in the past. This paper reviews the available literature on the design and construction considerations for kerbs and critically analyses them with a special focus on sustainable construction practice. The different materials commonly used around the world for the construction of kerb in terms of their properties, failure and available design guidelines have been discussed along with their management practice. Special situations, such as expansive soil movement and tree root-related problems, have also been considered, and the current guidelines for designing in such situations have also been discussed. A carbon footprint and sustainability analysis has been conducted on the current practice of using natural aggregate concrete and compared against several potential alternatives. The review of the design process indicated that the current practice relies on over-simplified design procedures and identified scopes for improvement, especially with the incorporation of mechanical behaviour of the material being used in construction. The carbon footprint and sustainability analysis indicated that the use of alternative materials could result in significant savings in the kerb construction industry’s carbon footprint.
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2013
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2018
Publisher: MDPI AG
Date: 16-10-2023
Publisher: American Society of Civil Engineers
Date: 21-03-2019
Publisher: Elsevier BV
Date: 04-2023
Publisher: American Society of Civil Engineers
Date: 21-03-2019
Publisher: Springer Science and Business Media LLC
Date: 10-10-2020
Publisher: Elsevier BV
Date: 08-2019
Publisher: Springer Science and Business Media LLC
Date: 10-12-2022
Publisher: Elsevier BV
Date: 2016
Publisher: American Society of Civil Engineers
Date: 18-07-2019
Publisher: WORLD SCIENTIFIC
Date: 05-2011
Publisher: Research Publishing Services
Date: 2013
Publisher: Springer International Publishing
Date: 11-2019
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 08-2023
Publisher: Springer International Publishing
Date: 11-2019
Publisher: MDPI AG
Date: 21-04-2022
DOI: 10.3390/SU14094970
Abstract: Permeable pavements allow rainfall and surface runoff to infiltrate through their surface, and this reduces urban flooding by increasing water management efficiency. The design of permeable pavements depends heavily on rainfall and soil conditions for a particular area. This study investigates the required base course thickness in different areas across Australia that can effectively reduce flood intensities. A detailed hydraulic analysis was conducted, considering the pavement materials, soil characteristics and rainfall intensities across Australia. The research also developed a relationship between base course thickness, rainfall intensity and soil classification, which can facilitate reasonable predictions of required design thickness for any location. The results showed a strong relationship between soil characteristics and pavement thickness, with clay soils requiring increased pavement thickness correlated with rainfall intensity. A spatial analysis was conducted, producing a tool for initial screening on the design requirements, before proceeding with a detailed design.
Publisher: Thomas Telford Ltd.
Date: 09-2021
Abstract: The discrete-element method (DEM) has gained popularity for developing a qualitative understanding of soil behaviour under a critical state soil mechanics (CSSM) framework. Most studies with a three-dimensional assembly of particles have used spheres as representative granular material to reduce computational demands. However, most granular materials – for ex le, sands – are not rounded, but possess features of angularity. Therefore, ellipsoid and cluster particles with different degrees of eccentricity were used in this study to evaluate the effect of the particle shape on the drained and undrained triaxial loading behaviour after isotropic and K 0 consolidation. The particle numerical properties and grain size distributions were kept the same for all specimens, irrespective of particle shape. The critical state data points for spheres and ellipsoids plotted on almost the same critical state line (CSL) in e–log(p′) space, whereas the CSLs of clusters plotted above them. Additionally, M lines shifted downward with increasing sphericity. It was also found that the stress ratio at the triggering of static liquefaction (η IS = q ′) in η IS –ψ space was affected by particle shape and consolidation path. The dilatancy (d = dε v p /dε q p ) was also affected by particle shape. It was found that dilatancy parameters for the SANISAND constitutive model are affected by particle shape, which may contribute to an improved understanding of particle shape in constitutive modelling.
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2023
Publisher: Canadian Science Publishing
Date: 10-2008
DOI: 10.1139/T08-064
Abstract: Void ratio has traditionally been used as a state variable for predicting the liquefaction behaviour of soils under the critical state soil mechanics framework. Recent publications show that void ratio may not be a good state variable for characterizing sand with fines. An alternative state variable referred to as the equivalent granular void ratio has been proposed to resolve this problem. To calculate this alternative state variable, a b parameter is needed. This b parameter represents the fraction of fines that actively participate in the force structure of the solid skeleton. However, predicting the value of b is problematic. Most, if not all, of the b values reported were determined by case-specific back-analysis, that is, the b value was selected so that a single correlation between equivalent granular void ratio and the measured steady state strength (or cyclic resistance) could be achieved. This paper examines the factors affecting the b value based on published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based on fines size and fines content. Published data appear to be in support of the proposed equation. A series of experiments were conducted on a specially designed sand–fines type to provide additional validation of the proposed equation and to reinforce the use of equivalent granular void ratio in a more generalized context.
Publisher: Springer Science and Business Media LLC
Date: 09-05-2022
Publisher: Thomas Telford Ltd.
Date: 05-2021
Abstract: The discrete-element method (DEM) was used to simulate constant-volume (undrained) triaxial compression tests for coarse particles (sand) mixed with non-plastic fines. Simulations were performed on granular mixtures with a range of fines contents (f c ) – namely, 0, 0·05, 0·10 and 0·20. The critical state and micromechanical responses of these mixtures were evaluated. The influence of f c on sand behaviour was captured when f c f thre , where f thre represents a threshold fines content, which corresponds to a transition from a fines-in-sand soil matrix to a sand-in-fines soil matrix. The DEM was utilised to assess the micromechanical participation of fines within the sand skeleton (matrix). Such evaluations led to assessing the performance of the equivalent granular void ratio (e*), the equivalent granular state parameter (ψ*) and ultimately their inherent parameter b, which represents the proportion of fines actively participating in the sand skeleton structure. It was observed that through capturing the stress partition of contact types within granular mixtures, a reasonable approximation of the active proportion of contacts within the sand matrix could be obtained. This led to a new DEM interpretation of the b parameter. The study therefore evaluated the concept and applicability of the equivalent state theory for sand–fines mixtures.
Publisher: MDPI AG
Date: 07-2022
DOI: 10.3390/PR10071306
Abstract: Pore water pressure changes due to soil-atmospheric boundary interaction can significantly influence soil behaviour and can negatively affect the safety and stability of geotechnical structures. For ex le, prolonged rainfall events can lead to increased pore water pressure and lower strength repeated cycles of pore water pressure changes can lead to degradation of strength. These effects are likely to become more severe in the future due to climate change in many parts of the world. To analyse the behaviour of soil subjected to atmospheric boundary interactions, several parameters are needed, and hydraulic conductivity is one of the more important and is difficult to determine. Hydraulic conductivity deduced from laboratory tests are often different from those from the field tests, sometimes by orders of magnitude. The problem becomes even more complicated when the soil state is unsaturated, where the hydraulic conductivity varies with the soil’s state of saturation. In this paper, a relatively simple alternative approach is presented for the estimation of the hydraulic conductivity of unsaturated soils. The method involved a systematic re-analysis of observed pore water pressure response in the field. Using a finite element software, the soil-atmospheric boundary interaction and related saturated/unsaturated seepage of an instrumented slope have been analysed, and results are compared with field measurements. The numerical model could capture the development of suction, positive pore water pressure and changes in water content with reasonable accuracy and demonstrated the usefulness of the hydraulic conductivity estimation method discussed in this paper.
Publisher: Elsevier BV
Date: 12-2016
Publisher: Springer Science and Business Media LLC
Date: 07-06-2023
DOI: 10.1007/S41101-023-00195-Y
Abstract: It is well accepted that moisture ingress in concrete reduces durability and life span of water assets. Condition assessment is an important tool to inform decision for maintenance, retrofit or replacement. However, the most significant challenge is to obtain accurate condition information, particularly when the inspection points are physically difficult to access or inaccessible. Therefore, a reliable and cost-effective monitoring (sensor) system, preferably real-time with ability to streaming online, would be a useful management tool, particularly for water utilities. This paper describes an approach to develop a distributed optical fibre humidly sensor for condition assessment and environmental monitoring both inside and outside of infrastructures, such as inside the concrete and surrounding soil. A new polyelectrolyte multilayer (PEM) coating with higher sensitive was evaluated for relative humidity measurement in soil and concrete, respectively. In this study, two simulated conditions, in concrete and soil, were conducted to evaluate the sensing concept with the development of appropriate measuring methodologies including fibre installation and protection. The optical fibre sensor setup in laboratory environment showed that optical sensor can detect and indicate voltage change with the variation of moisture contents in both soil and concrete. The test results indicate a good correlation between high levels of relative humidity/moisture and transmitted optical power. A simple relative humidity (RH) calibration can be used to convert signal to RH in percentage for soil and concrete measurements and the procedure used to imbed the fibre in both s les is effective. Nevertheless, the sensor measures soil humidity (not moisture content) therefore, further investigation is required to identify the consequence for the variation of the measured parameter.
Publisher: The Japanese Geotechnical Society
Date: 2015
DOI: 10.3208/JGSSP.OTH-09
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2013
Publisher: MDPI AG
Date: 22-02-2021
Abstract: Enzyme-induced carbonate precipitation (EICP) is a relatively new bio-cementation technique for ground improvement. In EICP, calcium carbonate (CaCO3) precipitation occurs via urea hydrolysis catalysed by the urease enzyme sourced from plants. EICP offers significant potential for innovative and sustainable engineering applications, including strengthening of soils, remediation of contaminants, enhancement of oil recovery through bio-plugging and other in situ field applications. Given the numerous potential applications of EICP, theoretical understanding of the rate and quantity of CaCO3 precipitation via the ureolytic chemical reaction is vital for optimising the process. For instance, in a typical EICP process, the rate and quantity of CaCO3 precipitation can depend significantly on the concentration, activity and kinetic properties of the enzyme used along with the reaction environment such as pH and temperature. This paper reviews the research and development of enzyme-catalysed reactions and its applications for enhancing CaCO3 precipitation in EICP. The paper also presents the assessment and estimation of kinetic parameters, such as the maximal reaction velocity (Vmax) and the Michaelis constant (Km), that are associated with applications in civil and geotechnical engineering. Various models for evaluating the kinetic reactions in EICP are presented and discussed, taking into account the influence of pH, temperature and inhibitors. It is shown that a good understanding of the kinetic properties of the urease enzyme can be useful in the development, optimisation and prediction of the rate of CaCO3 precipitation in EICP.
Publisher: Thomas Telford Ltd.
Date: 13-09-2022
Publisher: Thomas Telford Ltd.
Date: 05-2012
Publisher: American Society of Civil Engineers
Date: 09-10-2005
DOI: 10.1061/40787(166)15
Publisher: Springer International Publishing
Date: 28-10-2018
Publisher: Thomas Telford Ltd.
Date: 11-2014
Abstract: There have been significant advances in understanding of the effect of fines content, f c , on the mechanical response of sand with fines. The concepts of equivalent granular void ratio, e*, and equivalent granular state parameter, ψ*, which were developed for sands with fines, can be used in lieu of e and ψ to provide a unifying framework for characterising the undrained response of sands with low-plasticity fines, irrespective of f c . In addition, a recently developed constitutive model was able to capture the influence of both density, using e, and stress states on the stress–strain responses of clean sand under drained or undrained shearing with one set of parameters. This was achieved by rendering dilatancy and peak-failure stress ratio functions of ψ. The present work combines these two powerful unifying propositions, and by merely substituting e* and ψ* for e and ψ into the equations of the aforementioned model for clean sands, obtains a constitutive model for sand with fines that can capture the influence of f c , irrespective of density and stress states. The model-specific parameters were obtained from a few drained tests at a single fines content. Undrained responses for a range of f c and densities, with particular emphasis on liquefaction behaviour, were then predicted. For flow behaviour, the predictions agree well with experimental observations over a wide spectrum of initial conditions. The quality of the predictions reduces for limited flow behaviour. For non-flow behaviour, significant deviations were observed.
Publisher: Springer International Publishing
Date: 28-10-2018
Publisher: Springer International Publishing
Date: 28-10-2019
Publisher: MDPI AG
Date: 06-12-2022
DOI: 10.3390/SU142316282
Abstract: An increase in impermeable surface areas with urban development contributes to the rapid and large amount of surface runoff during rainfall. This often requires higher capacity stormwater collection systems, which can cause stress on the existing drainage system and this subsequently contributes to urban flooding. However, urban runoff can be reduced and managed for flood control and converted into a useful resource by harvesting and reusing the water. This can be achieved by switching from impermeable to permeable pavements. However, the amount of stormwater that can be harvested in a permeable pavement system depends on many factors, including rainfall, the water reuse demand and the materials used. This research aims to assess the requirements for permeable pavement design across Australia to balance demand, runoff reduction and construction requirements. A design approach employing the hydrological effects of the infiltration system was adopted for the analysis, along with a spatial analysis for a probabilistic prediction. A relationship was also established to predict a probable design thickness of pavement for various parameters. The research showed that in most Australian cities, for a 120 mm permeable pavement thickness, 40–80% of rainfall-runoff could be harvested, meeting about 10–15% of domestic water demand. The approach developed in this study can be useful for screening the potential of permeable pavements for water harvesting and for predicting spatially where a circular economic approach can be more efficient.
Publisher: American Society of Civil Engineers (ASCE)
Date: 02-2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2017
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: MDPI AG
Date: 10-08-2020
DOI: 10.32545/ENCYCLOPEDIA202008.0003.V1
Abstract: Microbial-induced calcite precipitation (MICP)& nbsp is a process that uses naturally occurring bacteria to bind soil particles together through calcium carbonate (CaCO3) precipitation. It is a promising new technology in the area of Civil Engineering with the potential to become a cost-effective, environmentally friendly, and sustainable solution to many problems such as ground improvement, liquefaction remediation, enhancing properties of concrete, and so forth.& nbsp
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: Springer Science and Business Media LLC
Date: 04-12-2013
Publisher: Springer International Publishing
Date: 28-10-2018
Publisher: Thomas Telford Ltd.
Date: 02-10-2023
Publisher: American Society of Civil Engineers
Date: 11-03-2011
Publisher: Thomas Telford Ltd.
Date: 12-2018
Abstract: The characteristic features of undrained responses of granular materials, for ex le, stress ratio at instability ( η IS ) and phase transformation ( η PT ) states and the critical state (CS) behaviour, are often influenced by the consolidation history. However, there are limited studies in the literature, and a consensus has not yet been reached. This study combined the triaxial test of yellow silty sand and the three-dimensional discrete element method (DEM) simulation of ellipsoid particles under a triaxial condition to evaluate the effect of isotropic and K 0 consolidations. Triaxial test data formed non-unique CS lines (CSLs) in the e–log(p′) space for isotropic and K 0 tests, whereas the CSL was unique for DEM simulations where e and p′ are the void ratio and mean effective stress, respectively. The micromechanical quantities, coordination number (C N ) and fabric anisotropy (F vM ) at the CS, also showed a unique relation with p′. The characteristic features, η IS and η PT , showed good correlation with the state parameter (ψ ) and the density indices. It was found that the η IS decreased with ψ, and the correlation was dependent on consolidation type. The micromechanical analysis suggested that F vM is a better parameter than C N to characterise the macromechanical behaviour. This study unambiguously supports the applicability of CS theory and provides insights into micromechanics of granular materials.
Publisher: Canadian Science Publishing
Date: 11-2013
Abstract: This paper presents experimental results on the effect of matric suction on the resilient modulus of four recycled unbound granular materials. The recycled materials were prepared at moisture contents ranging between 70% and 90% of optimum moisture content (OMC) and tested in a repeated load triaxial test (RLTT) apparatus under various stress regimes. Soil-water characteristic curves (SWCC) were established for each material by preparing s les at various moisture contents and measuring matric suction with filter papers. To obtain the wet end of the SWCC, further s les were conditioned on a tension plate at suctions controlled by the hanging water column method. Some published models for prediction of resilient modulus were applied to the experimental data, but the correlations were unsatisfactory generally, and so an improved model was sought. Subsequently, a model with four terms and six constants was developed, which followed the general power law. A single set of material constants was found for all recycled materials to provide satisfactory predictions of resilient modulus (R 2 = 0.88), over a wide range of stresses and moisture states.
Publisher: Canadian Science Publishing
Date: 03-2009
DOI: 10.1139/T08-122
Abstract: An experimental study was carried out to investigate the static liquefaction behaviour of sand with a small amount of plastic and nonplastic fines. Five series of tests were conducted in drained and undrained conditions. The drained test results indicate not only that the failure line coincides with the critical state, but also that the development of volumetric strain during shearing was not sensitive to the initial confining pressure. In both isotropically and anisotropically consolidated undrained tests, a so-called “reverse behaviour” was consistently observed. The results were also interpreted in the critical state framework. The critical and steady state (CS/SS) data were found to trace along the same curve in e–log( p′) space, irrespective of the stress history and effective stress paths. A comparison between the isotropic consolidation line (ICL) and critical state (CS) curve showed that a small amount of fines can significantly change the shape and position of the ICL relative to the CS curve. Furthermore, the soil behaviour manifested in both drained and undrained shearing led to the development of a modified state parameter.
Publisher: Elsevier BV
Date: 07-2023
Publisher: Informa UK Limited
Date: 12-04-2010
Publisher: Elsevier BV
Date: 07-2023
Publisher: Elsevier BV
Date: 2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2014
Publisher: Elsevier BV
Date: 03-2020
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2012
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: American Society of Civil Engineers
Date: 17-03-2022
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2019
Publisher: American Society of Civil Engineers
Date: 21-02-2020
Publisher: Springer Singapore
Date: 2021
Publisher: MDPI AG
Date: 06-12-2022
DOI: 10.3390/GEOSCIENCES12120449
Abstract: Soil liquefaction or instability, one of the most catastrophic phenomena, has attracted significant research attention in recent years. The main cause of soil liquefaction or instability is the reduction in the effective stress in the soil due to the build-up of pore water pressure. Such a phenomenon has often been thought to be related to the undrained shearing of saturated or nearly saturated sandy soils. Notwithstanding, many researchers also reported soil instability under a drained condition due to the reduction in lateral stress. This condition is often referred to as the constant shear drained (CSD) condition, and it is not uncommon in nature, especially in a soil slope. Even though several catastrophic dam failures have been attributed to CSD failure, the failure mechanisms in CSD conditions are not well understood, e.g., how the volumetric strain or effective stress changes at the triggering of flow deformation. Researchers often consider the soil fabric to be one of the contributors to soil behaviour and use this parameter to explain the failure mechanism of soil. However, the soil fabric is difficult to measure in conventional laboratory tests. Due to that reason, a numerical approach capable of capturing the soil fabric, the discrete element method (DEM), is used to investigate the CSD shearing mechanism. A series of simulations on 3D assemblies of ellipsoid particles was conducted. The DEM specimens exhibited instability behaviour when the effective stress paths nearly reached the critical state line. It can be clearly observed that the axial and volumetric strains changed suddenly when the stress states were close to the critical state line. Alongside these micromechanical observations, the study also presents deeper insights into soil behaviour by relating the macro-observations to the micromechanical aspect of the soil.
Publisher: Springer Science and Business Media LLC
Date: 2023
DOI: 10.1007/S11709-022-0850-0
Abstract: The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.
Publisher: Thomas Telford Ltd.
Date: 12-2020
Abstract: The overall effectiveness of bio-cementation techniques such as microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP) can be different due to different sources of urease enzyme and treatment approach used. This paper compares the behaviour of oven-dried MICP and EICP-treated sand from macro- and micro-mechanical point of view with the number of treatment cycles and average calcium carbonate (CaCO 3 ) content used as a comparison basis. The results indicate that in both processes, the calcium carbonate content increased with the number of treatment cycles and led to an improvement in strength (unconfined compressive and splitting tensile strength) and stiffness. For similar average calcium carbonate content, EICP-treated s les showed significantly higher splitting tensile strength (compared to MICP) even though a slightly smaller amount of precipitates were observed at particle contacts through scanning electron microscopy. This indicates, besides the average calcium carbonate content, its distribution along the height of the s le is likely to have a significant contribution towards the strength. X-ray powder diffraction and energy-dispersive X-ray spectroscopy analyses confirmed that precipitated calcium carbonate in both types of treatments were mainly calcite crystals with minor traces of aragonite.
Publisher: Springer Science and Business Media LLC
Date: 06-11-2011
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Society of Civil Engineers
Date: 23-03-2023
Publisher: Springer Science and Business Media LLC
Date: 13-10-2020
Publisher: Springer Science and Business Media LLC
Date: 23-11-2016
Publisher: American Society of Civil Engineers
Date: 23-03-2023
Publisher: Trans Tech Publications, Ltd.
Date: 12-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.629.433
Abstract: A stochastic analysis that incorporates spatial variability of material parameter of clay i.e. undrained shear strength, c within the finite element analysis was done. A smoother change of c between two neighbouring soil elements is expected than two elements at a distance apart, thus a spatial correlation length is used within the random field to describe the distance over which random values tend to be correlated. When the correlation lengths in horizontal and vertical directions are same, the soil elements can be described ‘isotropic’. Most of the previous studies investigated the effect of variation of c in terms of coefficient of variation, COV (standard deviation/mean) and the isotropic correlation length on bearing capacity. However, the correlation length of soil may not be isotropic as they may be deposited in layers i.e. correlation length in horizontal direction may be higher than that in vertical direction. Thus, this study investigated the effect of isotropic as well as anisotropic (in terms of correlation length) conditions and their lengths over a range of COV of c on the bearing capacity. The result of this study would help to understand the effect of soil anisotropy on bearing capacity.
Publisher: American Society of Civil Engineers (ASCE)
Date: 04-2019
Publisher: CRC Press
Date: 28-04-2023
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: Springer India
Date: 29-08-2015
Publisher: Elsevier BV
Date: 07-2021
Publisher: Springer Singapore
Date: 04-09-2020
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: American Society of Civil Engineers
Date: 24-02-2014
Publisher: Springer Science and Business Media LLC
Date: 08-2023
Publisher: Canadian Science Publishing
Date: 08-2012
DOI: 10.1139/T2012-045
Abstract: The underlying mechanism of static and cyclic liquefaction of loose contractant sandy soil is unstable behaviour associated with deviatoric strain-softening. Such unstable (strain-softening) behaviour has been referred to as static or cyclic instability depending on whether the loading condition is monotonic or cyclic. Past research into linkage between static instability and cyclic instability of sand with fines is based largely on comparing monotonic and one-way cyclic loading behaviour of specimens of the same void ratio and fines content. In this article, the authors attempt to link the condition that defines triggering of cyclic instability to that of static instability of specimens of different void ratios and fines contents. This is achieved by the proposed concept of equivalent granular state parameter. Two specimens are considered as equivalent if they have the same equivalent granular state parameters at the start of undrained shearing. The effective stress ratio at triggering of static instability can be used to predict impending cyclic instability of an equivalent specimen of different fines content and void ratio. This linkage between static and cyclic instability was evaluated for a wide range of fines contents, initial mean effective stresses, and types of cyclic loading. The last factor includes symmetrical and nonsymmetrical two-way cyclic loading.
Publisher: MDPI AG
Date: 24-08-2021
DOI: 10.3390/SU13179521
Abstract: Impact resistance, water transport properties and sodium sulphate attack are important criteria to determine the performance of concrete incorporating mixed types of recycled plastic waste. Nine mixes were designed with different combinations of the three plastic types Polyethylene terephthalate (PET), High density polyethylene (HDPE) and Polypropylene (PP). The plastic partially substituted the coarse aggregate (by volume) at various replacement ratios 10%, 15%, 20% and 30%. The impact resistance and water transport properties were evaluated for nine mixes while sodium sulphate attack test was performed for three mixes. The results showed that the addition of mixed recycled plastic in concrete improved the impact resistance. The highest impact resistance improvement was achieved by R8 (PET + HDPE + PP) at 30% replacement which was 4.5 times better than the control mix. Water absorption results indicated a slight increase in all plastic mixes while contradictory results were observed for sorptivity test. Analysis of sodium sulphate attack results showed that incorporating 30% mixed plastic reduced the sodium sulphate resistance slightly due to the collective effect of plastic entrapping of sulphate ions after 80 cycles. This study has shown some positive results relating to the impact performance of Mixed Recycled Plastic Concrete (MRPC) which enhances its use in a sustainable way.
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 03-2015
Publisher: WORLD SCIENTIFIC
Date: 05-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 06-2019
Publisher: Frontiers Media SA
Date: 18-07-2023
DOI: 10.3389/FEART.2023.1165685
Abstract: Heavy metals in landfill leachate are easily adsorbed by soil particles, causing serious threats to human health and surrounding environments. Mining and metallurgy activities are intensive in Northwest China, thereby enlarging threats. The aim of the present study is to enhance our knowledge about the linkage between the microstructural evolution of the loess soil induced by lead contamination and the macro air and liquid permeability properties. A series of air and liquid permeability tests on the uncontaminated and Pb-contaminated loess specimens were conducted. Their air and liquid permeability properties were evaluated on the basis of Darcy’s law and the soil–water retention curves, respectively. The microstructural evolution, when subjected to low and high Pb 2+ concentrations, was assessed using scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and zeta potential tests. The intrusion of Pb 2+ decreases the absolute zeta potential ζ, which in turn leads to a more distinct agglomerated structure and higher intrinsic permeability. Moreover, the dedolomitization and associated cerussite (PbCO 3 ) precipitation are deemed as the main cause of micropore clogging, whereas the corrosion of the cement between soil particles by H + shows a good correspondence to an increase in the number of mesopores. With the concentration of Pb 2+ increasing from 0 to 2,000 mg/kg, the proportion of micropores decreases from 37.9% to 15.1%, and the proportion of mesopores increases from 17.3% to 53.3%. In addition, the air entry value decreased from 19.5 to 12.8 kPa, indicating that the water retention behavior decreased. The findings highlight the impacts of lead contamination on the microstructure and macro permeability properties and give some design guideposts to heavy metal-contaminated site remediation.
Publisher: American Society of Civil Engineers (ASCE)
Date: 04-2014
Publisher: American Society of Civil Engineers
Date: 14-05-2008
DOI: 10.1061/40975(318)90
Publisher: Thomas Telford Ltd.
Date: 09-2021
Abstract: Enzyme-induced carbonate precipitation (EICP) is a bio-cementation technique and a sustainable method of ground improvement. This study examines the influence of the concentrations of substrates [S 0 ] and enzymes [E 0 ] as well as enzyme activity (A E ) on the calcium carbonate (CaCO 3 ) precipitation ratio (PR) using 130 test-tube experiments. It was found that the effect of enzyme concentration and activity on PR can be explained using a normalisation of [E s ] = [E 0 ] × A E , where [E s ] is the adjusted enzyme concentration. PR increased non-linearly with increasing [E s ]/[S 0 ] and reached 100% at a threshold [E s ]/[S 0 ] value of approximately 20 kU/mol. An exponential function was developed that could capture the relationship between PR and [E s ]/[S 0 ] with reasonable accuracy. This observation was further evaluated with data from the literature consisting of a further 100 test-tube experiments. EICP solutions consisting of [E s ]/[S 0 ] = 20 kU/mol were found to be optimum for soil treatment. The established function was later extended to predict strength gain as measured by the unconfined compressive strength (UCS) and the splitting tensile strength (STS) for EICP-treated soils and could predict the strength gain (UCS/STS) with reasonable accuracy. Results from scanning electron microscopy images, energy-dispersive X-ray spectroscopy and X-ray powder diffraction showed that the precipitated calcium carbonate in test tubes and treated soil was mostly calcite crystals with different morphologies, possibly due to the level of purity of the urease enzyme used.
Publisher: American Society of Civil Engineers
Date: 17-03-2022
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 04-2018
Publisher: American Society of Civil Engineers
Date: 23-03-2023
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 05-2022
Publisher: MDPI AG
Date: 04-08-2020
DOI: 10.3390/SU12156281
Abstract: Microbial-induced calcite precipitation (MICP) is a promising new technology in the area of Civil Engineering with potential to become a cost-effective, environmentally friendly and sustainable solution to many problems such as ground improvement, liquefaction remediation, enhancing properties of concrete and so forth. This paper reviews the research and developments over the past 25 years since the first reported application of MICP in 1995. Historical developments in the area, the biological processes involved, the behaviour of improved soils, developments in modelling the behaviour of treated soil and the challenges associated are discussed with a focus on the geotechnical aspects of the problem. The paper also presents an assessment of cost and environmental benefits tied with three application scenarios in pavement construction. It is understood for some applications that at this stage, MICP may not be a cost-effective or even environmentally friendly solution however, following the latest developments, MICP has the potential to become one.
Publisher: Thomas Telford Ltd.
Date: 21-09-2023
Abstract: Microbial or enzyme-induced calcium carbonate precipitation (MICP/EICP) are relatively new ground improvement technique. In this study, the mechanical behaviour of biotreated (MICP/ EICP) and untreated sands were investigated in light of the critical state soil mechanics framework using a series of direct simple shear (DSS) tests. A wide range of CaCO 3 content (C C ), initial void ratio after consolidation (e 0 ) and effective initial normal stress (σ′ N 0 ) was considered. The biotreated specimens showed improved shear strength and dilative tendency compared to untreated specimens with similar initial states. The ultimate state for the biotreated sand shifted towards a smaller void ratio (e) than e at the critical state of untreated sand at the same σ′ N in e–log σ′ N space. Compared to untreated sand, a significantly larger ultimate state stress ratio was achieved for the biotreated sand, particularly at high C C and low σ′ N 0 . The characteristic features of undrained behaviour, such as instability stress ratio, stress ratio at phase transformation and flow potential showed good relationships with modified initial state parameter, void ratio after biotreatment and C C . Bonding ratio, (τ/σ′ N ) bond was used to quantify the interparticle bonding. The peak value of (τ/σ′ N ) bond for the biotreated sand was significantly larger than zero, particularly at high C C and low σ′ N 0 , while the peak (τ/σ′ N ) bond for the untreated sand was negligible. It is also observed that the mobilisation and degradation of CaCO 3 bonds in biotreated sand during DSS shearing are influenced by both C C and σ′ N 0 .
Publisher: Informa UK Limited
Date: 09-2012
Publisher: Informa UK Limited
Date: 22-08-2008
Publisher: American Society of Civil Engineers
Date: 11-03-2011
Publisher: American Society of Civil Engineers
Date: 29-03-2012
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Elsevier BV
Date: 03-2015
Publisher: Frontiers Media SA
Date: 17-02-2023
DOI: 10.3389/FBUIL.2023.1117858
Abstract: Soil is a naturally heterogeneous material and can show significant spatial variation in strength and other properties. For silty and clayey soils, these variations are often more pronounced. Despite such variation, many past studies considered these soils as homogeneous and only considered a single set of soil parameters. This may lead to underestimation of the failure potential of geo-structure such as natural slopes, water retaining dams, retaining walls, etc. A finite element method considering soil variability should be an ideal tool to investigate the behaviour of these soils. This study adopted a 2D random finite element method to evaluate the effect of such variability on slope stability. The spatial variability was implemented by using the coefficient of variation ( COV ) and the spatial correlation length ( θ ) for cohesion. It was found that the soil slope with higher COV would have a higher chance of failure, whereas the soil slope with less COV might not show any failure. In addition, the soil with a higher θ , in general, show less potential of failure. In the literature, most studies considered an isotropic condition for the soil, i.e., θ in x and y directions are the same θ x = θ y , which is not realistic. Therefore, the soil anisotropy (i.e., θ x ≠ θ y ) was considered carefully in this study. It was found that the probability of failure for anisotropic soil might be significantly higher than the isotropic soil.
Publisher: MDPI AG
Date: 04-08-2020
DOI: 10.3390/SU12156284
Abstract: Particulate Matter (PM) pollution is generally considered as a prime indicator of urban air quality and is linked to human health hazards. As vehicles are a vital component of an urban setting, the risks of particulate pollution need to be assessed. An emission modelling is essential for that, and thus stochastic modelling approach involving Monte Carlo simulation technique was applied, aiming to reduce the uncertainty in emission modelling. The risks scenarios for the emissions were generated for 2019 (present state) and 2024 (future), integrating the probability of emissions and the associated AQI (Air Quality Index). Despite the vehicles being a minor source of PM in Dhaka (compared to the contribution from other sources), about one-third of the city is found under high risk due to the exhaust particulate pollution having the potentiality to cover more than 60% of the city in the coming years, affecting the urban public health sustainability. However, the extent of implementation of planning and management strategies can revert the scenarios for the city, which can plausibly reduce the risk from 80% to 50%, or even to a no-risk state.
Publisher: Springer Science and Business Media LLC
Date: 08-2021
Publisher: MDPI AG
Date: 06-12-2021
DOI: 10.3390/SU132313479
Abstract: Many roads that were initially designed for relatively low traffic volumes need re-surfacing or partial replacement of the unbound granular material to satisfy current traffic demand. Significant research efforts based on laboratory studies have been seen in the literature to characterize the suitability of virgin materials, which is relatively expensive and unsustainable. Therefore, the object of this study is the in situ recycling of existing materials in two road sections by improving their properties with a suitable additive. A hydrophobic synthetic polymer was chosen for two trials due to the high plasticity of fines of the in situ materials and a high chance of water intrusion in the low-lying plains in Adelaide. The extensive laboratory characterization shows that hydrophobicity is imparted in capillary rise tests, improved drainage in permeability tests, and greater matric suction at the same moisture content. Furthermore, the unconfined compressive strength was increased. The repeated loading triaxial testing showed higher stiffness and lowered permanent strain to withstand higher traffic volume. In general, in situ recycling is adaptable and considered to be cheaper and sustainable. The estimated current costs and carbon footprints are presented for re-construction and in situ recycling with dry powder polymer, or solely with lime, to help construction planning.
Location: Australia
Start Date: 2016
End Date: 2018
Funder: Australian Research Council
View Funded ActivityStart Date: 09-2017
End Date: 06-2023
Amount: $630,000.00
Funder: Australian Research Council
View Funded Activity