ORCID Profile
0000-0002-5318-3862
Current Organisation
University of South Australia
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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: Elsevier BV
Date: 03-2014
Publisher: Springer Netherlands
Date: 2013
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: 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: Informa UK Limited
Date: 21-01-2019
Publisher: Elsevier BV
Date: 09-2013
Publisher: Springer Singapore
Date: 2020
Publisher: Springer Science and Business Media LLC
Date: 03-12-2022
Publisher: American Society of Civil Engineers
Date: 21-02-2020
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: 04-09-2020
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: Thomas Telford Ltd.
Date: 06-2020
Abstract: This study investigated the non-linear void ratio–log(time) relationship during creep (secondary compression) under a range of loading history. Four long-duration creep tests on reconstituted clay soils from two different sites were performed. Data from tests reported in the literature (six long-duration creep tests on reconstituted marine deposits and three long-duration creep tests on undisturbed soil s les) were also used in this investigation. A creep coefficient function that depends on both the stress state and extent of creep is proposed. According to the function, the creep rate slows down with its progression.
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: American Society of Civil Engineers (ASCE)
Date: 07-2023
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 International Publishing
Date: 29-10-2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: Springer Science and Business Media LLC
Date: 13-10-2020
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: 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: MDPI AG
Date: 16-10-2023
Publisher: Informa UK Limited
Date: 15-07-2013
Publisher: American Society of Civil Engineers
Date: 21-03-2019
Publisher: Springer Science and Business Media LLC
Date: 11-2022
DOI: 10.1038/S41591-022-02047-Z
Abstract: Circulating tumor DNA (ctDNA) sequencing guides therapy decisions but has been studied mostly in small cohorts without sufficient follow-up to determine its influence on overall survival. We prospectively followed an international cohort of 1,127 patients with non-small-cell lung cancer and ctDNA-guided therapy. ctDNA detection was associated with shorter survival (hazard ratio (HR), 2.05 95% confidence interval (CI), 1.74-2.42 P < 0.001) independently of clinicopathologic features and metabolic tumor volume. Among the 722 (64%) patients with detectable ctDNA, 255 (23%) matched to targeted therapy by ctDNA sequencing had longer survival than those not treated with targeted therapy (HR, 0.63 95% CI, 0.52-0.76 P < 0.001). Genomic alterations in ctDNA not detected by time-matched tissue sequencing were found in 25% of the patients. These ctDNA-only alterations disproportionately featured subclonal drivers of resistance, including RICTOR and PIK3CA alterations, and were associated with short survival. Minimally invasive ctDNA profiling can identify heterogeneous drivers not captured in tissue sequencing and expand community access to life-prolonging therapy.
Publisher: American Society of Civil Engineers
Date: 21-03-2019
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 02-2021
Publisher: Informa UK Limited
Date: 09-2011
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: IOP Publishing
Date: 09-09-2015
Publisher: American Society of Civil Engineers
Date: 29-03-2012
Publisher: Canadian Science Publishing
Date: 03-2014
Abstract: Behaviour of two embedded piles subjected to passive loading due to construction of an embankment was modelled in this paper. The piles were installed at the berm section of an embankment in a later stage of its construction. The investigation was carried out using a combination of two- and three-dimensional analyses. The analysis results were compared with the field-measured values and they agreed well.
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: Canadian Science Publishing
Date: 02-2010
DOI: 10.1139/T09-087
Abstract: This paper presents modelling of the consolidation of foundation soil under a wide embankment constructed over soft soil. An elastic–viscoplastic (EVP) constitutive model is used to represent the foundation soil for the coupled finite element analysis (FEA). A unit-cell analysis is carried out to capture the maximum settlement and the development of excess pore-water pressure with time below the centreline of the embankment for a long period (9 years). A new function for capturing the varying nature of the creep or secondary compression coefficient is proposed and used in association with the EVP model. The input material parameters for this study were determined from extensive laboratory experiments except for the equivalent horizontal permeability, which was systematically estimated by using vertical permeability data obtained from one-dimensional consolidation tests and by back-analysing the first 12 months of field settlement data. Comparisons are made among the predictions obtained adopting an elastoplastic modified Cam clay model and the EVP model with constant and varying creep coefficients for the foundation soil and the corresponding field data. The predictions with the EVP model are found to be better than those with the elastoplastic model and the use of a varying creep coefficient for the EVP model seems to further improve its predicting ability.
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: 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: Springer International Publishing
Date: 28-10-2018
Publisher: Elsevier BV
Date: 11-2018
Publisher: Springer International Publishing
Date: 28-10-2018
Publisher: Canadian Science Publishing
Date: 05-2011
DOI: 10.1139/T10-104
Abstract: The consolidation of the soft foundation soil of a geogrid-reinforced embankment, improved with prefabricated vertical drains (PVDs), is modelled in this paper using two-dimensional (2D) plane strain coupled finite element (FE) analysis to predict long-term multiple behaviour characteristics (e.g., settlement, lateral displacement, excess pore-water pressure response, geosynthetic strain) of the embankment. Two sets of analyses were carried out with the foundation soil being modelled using relatively simple elastic–viscoplastic (EVP) models. A nonlinear creep function was used in association with them. The input material parameters were determined from extensive laboratory testing or were taken from reliable sources except for the horizontal permeability, which was systematically back-estimated using oedometer test data and the first year of field settlement data. The results from both analyses were compared with the long-term (up to 6 years) field-monitoring data and were found to be in good agreement with the field measurements.
Publisher: Springer International Publishing
Date: 28-10-2019
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Md Rajibul Karim.