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Recent publications in Engineering

Wheatley, Greg, and Rubel, Robiul Islam (2021) Analysis of conveyor drive power requirements in the mining industry. Acta logistica. (In Press)
This article presents the analysis of conveyor drive power requirements for three typical mining conveyors. One of the conveyors was found not to be able to start when fully loaded. The analysis indicates that two of the conveyors are adequately powered while one is underpowered. This was found to be primarily the result of the maximum tonnage of the two adequately powered conveyors being 1500 tonnes per hour (TPH) while the inadequately powered conveyor was classed with a maximum tonnage of 1800 TPH. It is recommended that the current draw for each motor when fully loaded be measured. This will be compared to the design. Further analysis was done to allow 2000 TPH on all conveyors. The required upgraded drive size is presented. This article does not address the structural adequacy of the supporting structure. Rather, only the capabilities of the conveyor belt and drives to transport the required TPH.

Vuppaladadiyam, Arun K., Antunes, Elsa, Sanchez, Paula Blanco, Duan, Huabo, and Zhao, Ming (2021) Influence of microalgae on synergism during co-pyrolysis with organic waste biomass: a thermogravimetric and kinetic analysis. Renewable Energy. (In Press)
The synergistic influence of microalgae on the two forms of organic waste biomasses, namely biomass wastes (BW) and its digested form (DBW), during co-pyrolysis was evaluated based on the thermal decomposition behaviour, gas yields, extent of thermal decomposition and reaction kinetics. The biomasses and their blends were co-pyrolysed at three different heating rates (10, 15 and 20C/min) in a thermogravimetric analyzer coupled with a mass spectrometer. Initial assessment, based on TG-DTG data, revealed that the thermal degradation can be divided into three zones (50-150C, 150-550C and 550-800C) for all the biomasses and their blends. The thermogravimetric data was used to evaluate the kinetic triplet, which include apparent activation energy (Ea), pre-exponential factor (A) and reaction mechanism, f(a). Semi-quantitative method was used to quantify the gas species, H2, CO2 and CO were dominant species, implying the water gas reactions and oxidation reactions were predominant. The synergistic influence of microalgae was clearly evident in terms of reaction kinetics, as noted in the reduction in the apparent activation energy and increase in the total gas yields. The obtained kinetic triplet and thermodynamic parameters are expected to facilitate the design and optimization of co-pyrolysis of microalgae with other forms of organic wastes.

Varsha, S.S.V., Vuppaladadiyam, Arun K., Shehzad, Farrukh, Ghaedi, Hosein, Murugavelh, S., Dong, Weiguo, and Antunes, Elsa (2021) Co-pyrolysis of microalgae and municipal solid waste: a thermogravimetric study to discern synergy during co-pyrolysis process. Journal of the Energy Institute, 94. pp. 29-38.
Synergism during the co-pyrolysis of microalgae (CC), municipal solid waste (MSW), and their blends(CC/MSW) (w/w %), 25/75 (CM-1), 50/50 (CM-2), and 75/25 (CM-3), was evaluated based on thermal decomposition pattern, evolved gases, rate and extent of thermal decomposition, and kinetic parameters. Three stages of devolatilization attributed to dehydration, devolatilization of major structural com-pounds of biomass and decomposition of solid residues were noticed during the co-pyrolysis of biomass samples. The main pyrolysis stages for CC, MSW, CM-1, CM-2 and CM-3 were 175e520, 151-523, 164-504,168-510, 160e501 °C, respectively. Microalgae, CC, appeared to be thermally resistant, while MSW is noticed to be thermally sensitive. The kinetics analysis was studied by deconvoluting the DTG profile into independent stages, followed by application of isoconversional methods to evaluate the activation energy and the pre-exponential factor. Furthermore, the reaction mechanism of each stage was determined by using the master plot method. The semi-quantitative method was used to evaluate the evolved gases and CO, CO2 and H2 were noticed to be the dominant gas species. The obtained thermal and kinetic data for co-pyrolysis of microalgae and MSW can serve are basis for scale-up and reactor design of pyrolysis process for similar kind of waste streams.

Islam, Md Anwarul, Jacob, Mohan V., and Antunes, Elsa (2021) A critical review on silver nanoparticles: from synthesis and applications to its mitigation through low-cost adsorption by biochar. Journal of Environmental Management, 281. 111918.
Silver nanoparticles are one of the most beneficial forms of heavy metals in nanotechnology applications. Due to its exceptional antimicrobial properties, low electrical and thermal resistance, and surface plasmon resonance, silver nanoparticles are used in a wide variety of products, including consumer goods, healthcare, catalysts, electronics, and analytical equipment. As the production and applications of silver nanoparticles containing products increase daily, the environmental pollution due to silver nanoparticles release is increasing and affecting especially the aqueous ecosystem. Silver nanoparticles can kill useful bacteria in soil and water, and bioaccumulate in living organisms even at low concentrations from 10−² to 10 μg/mL silver can show antibacterial effect. On the other hand, the maximum silver discharge limit into freshwater is 0.1 μg/L and 3.2 μg/L for Australia and the USA, respectively. To reduce its toxic consequences and meet the regulatory guidelines, it is crucial to remove silver nanoparticles from wastewater before it is discharged into other water streams. Several technologies are available to remove silver nanoparticles, but the adsorption process using low-cost adsorbents is a promising alternative to mitigate silver nanoparticle pollution in the bulk stage. As one of the low-cost adsorbents, biochar produced from the biomass waste could be a suitable adsorbent. This review focuses on collating the latest evidence on silver nanoparticle production, applications, environmental consequences, and cost-effective technological approaches for silver removal from wastewater.

Tuladhar, Rabin, Marshall, Amelia, and Sivakugan, Siva (2020) Use of recycled concrete aggregate for pavement construction. In: Pacheco-Torgal, Fernando, Ding, Yining, Colangelo, Francesco, and Tuladhar, Rabin, (eds.) Advances in Construction and Demolition Waste Recycling: Management, Processing and Environmental Assessment. Woodhead Publishing . Elsevier, Duxford, United Kingdom, pp. 181-197.
Construction and demolition (C&D) wastes comprise waste generated from construction, renovation, and demolition of buildings, roads, and other infrastructures, and excavation of land associated with construction activities (QDERM, 2011). C&D wastes include a wide range of different waste materials such as concrete, asphalt, bricks, tiles, timber, steel, and soil. In 2016/2017, 20.4 Mt of C&D wastes were produced in Australia, which accounts for more than 40% of Australia’s total annual waste (Pickin et al., 2018). Hydraulically bound materials are made by mixing aggregates and granular aggregates with cement as a binding material. On the other hand, unbound pavement materials consist of quarry materials, natural gravels, and recycled materials without the use of binding materials like cement. Unbound granular materials are the most commonly used material for base/subbase construction in Australia owing to their strength, ease in construction, and low cost. Traditionally, natural crushed rocks are used as granular unbound material for road base and subbase constructions. With the increasing scarcity of natural aggregates and the need to reduce the waste going into landfills, alternative sustainable materials such as recycled C&D wastes are increasingly being considered as a substitute for natural aggregates.

Bodhinayake, G.G., Ginger, J.D., and Henderson, D.J. (2020) Net cladding pressures on industrial building roofs. In: Lecture Notes in Civil Engineering (37) pp. 1077-1085. From: ACMSM25: 25th Australasian Conference on Mechanics of Structures and Materials, 4-7 December 2018, Brisbane, QLD, Australia.
The net wind pressure on roof cladding of metal clad buildings are critical for structural design. Large openings on the windward wall generate large positive internal pressure, which in combination with high external suction pressure produces large net negative pressure on the roof. Wind tunnel studies conducted on a 1:200 scale industrial building model and analytical methods were used to analyze combination effects of internal and external pressures on roof cladding. AS/NZS 1170.2 gives conservative net pressures on the windward roof edge of buildings, for quartering approach wind. The combination factor ( f_C= C_(p ̌,net)/(C_(p ̌e)- C_(p ̂i) )) varies depending on location of the cladding element and position and type of opening(s) in the envelope. The calculated f_C factors are 5% less than the combination factor in the AS/NZS 1170.2 for roof cladding of nominally sealed buildings while it is 5% to 10% less than the building with the large opening. Helmholtz resonance occurs in the building with large opening and internal pressure influences energy contained in the net pressure at the Helmholtz frequency. External suction pressures on windward roof edge and positive internal pressures in the building with large windward wall opening are negatively correlated whilst of external and internal pressures are positively correlated, in the nominally sealed building

Brice, Sara M., Phillips, Elissa J., Millett, Emma L., Hunter, Adam, and Philippa, Bronson (2020) Comparing inertial measurement units and marker-based biomechanical models during dynamic rotation of the torso. European Journal of Sport Science, 20 (6). pp. 767-775.
Inertial measurement units (IMUs) enable human movements to be captured in the field and are being used increasingly in high performance sport. One key metric that can be derived from IMUs are relative angles of body segments which are important for monitoring form in many sports. The purpose of this study was to a) examine the validity of relative angles derived from IMUs placed on the torso and pelvis; and b) determine optimal positioning for torso mounted sensors such that the IMU relative angles match closely with gold standard torso-pelvis and thorax-pelvis relative angle data derived from an optoelectronic camera system. Seventeen adult participants undertook a variety of motion tasks. Four IMUs were positioned on the torso and one was positioned on the pelvis between the posterior superior iliac spines. Reflective markers were positioned around each IMU and over torso and pelvis landmarks. Results showed that the IMUs are valid with the root mean square errors expressed as a percentage of the angle range (RMSE%) ranging between 1% and 7%. Comparison between the IMU relative angles and the torso-pelvis and thorax-pelvis relative angles showed there were moderate to large differences with RMSE% values ranging between 4% and 57%. IMUs are highly accurate at measuring orientation data; however, further work is needed to optimize positioning and modelling approaches so IMU relative angles align more closely with relative angles derived using traditional motion capture methods.

Kumar, Avishek, Al-Jumaili, Ahmed, Prasad, Karthika, Bazaka, Kateryna, Mulvey, Peter, Warner, Jeffrey, and Jacob, Mohan (2020) Pulse plasma deposition of Terpinen-4-ol: an insight into polymerization mechanism and enhanced antibacterial response of developed thin films. Plasma Chemistry and Plasma Processing, 40. pp. 339-355.
Antifouling/antibacterial coating derived from a sustainable natural resource for biomedical devices have shown promising outcomes, especially in the prevention of bacterial growth. Herein, pulse-plasma chemical vapour deposition is used to fabricate antimicrobial coatings from Terpinen-4-ol, a tea tree oil-based precursor. In this manuscript, during RF plasma polymerisation, pulsed plasma is used to retain the pristine monomer structure in the developed stable coating and thereby enhance its antibacterial activity. The developed films have tunable physical and chemical properties. Diverse film surface properties were obtained by varying the plasma deposition parameters, mainly the deposition mode (pulse and continuous wave) and duty cycle. The role of film wettability on degree of bacterial attachment has been elucidated. Overall, the number of viable bacteria on all the deposited coatings (25-30%) were reduced to half with respect to the control (56%).

Al Nahain, Abdullah, Ignjatovic, Vera, Monagle, Paul, Tsanaktsidis, John, Vamvounis, George, and Ferro, Vito (2020) Anticoagulant heparin mimetics via RAFT polymerization. Biomacromolecules, 21 (2). pp. 1009-1021.
Heparin, a sulfated polysaccharide derivedfrom animal sources, is the most commonly used parenteralanticoagulant drug, but it suffers from significant safety andsupply issues. Herein, we describe the preparation of heparinmimetic homo- and copolymers via the reversible addition−fragmentation chain transfer (RAFT) polymerization in waterof commercially available (non-carbohydrate) sulfonated andcarboxylated monomers. The anticoagulant activities of thepolymers were assessed by activated partial thromboplastintime (APTT), thrombin clotting time (TCT), and for the more promising polymers, thrombin generation, antifactor Xa, andantifactor IIa assays. Sulfonated homopolymers studied herein displayed low cytotoxicity and significant anticoagulant activity inAPTT, TCT, and thrombin generation assays. In addition, copolymers of sodium styrenesulfonate and acrylic acid [poly(SSS-co-AA)] displayed unprecedented antifactor IIa activity. This study demonstrates the potential of RAFT polymers as lternativeanticoagulants for biomedical applications.

Lal, Alvin, and Datta, Bithin (2020) Optimal pumping strategies for the management of coastal groundwater resources: application of Gaussian Process Regression metamodel-based simulation-optimization methodology. ISH Journal of Hydraulic Engineering. (In Press)
The present study utilizes a coupled simulation-optimization (S-O) methodology to develop a multi-objective management strategy for a coastal aquifer system. The aim of the multi-objective management model is to maximize pumping from freshwater wells (FWs) and minimize pumping from the barrier wells (BWs), while keeping salinity concentration in the aquifer within pre-specified limits (optimization constraint). To achieve computational feasibility of the management model, the numerical simulation model is substituted by the relatively new Gaussian Process Regression (GPR) metamodels. The GPR models are used to approximate coastal aquifer responses to variable transient pumping patterns from FWs and BWs. Prediction capabilities of the developed GPR metamodels are quantified using standard statistical parameters. Once trained and validated, the GPR metamodels are coupled to a multi-objective genetic algorithm optimization model and used to prescribe optimal groundwater pumping patterns. The outcomes of this study establishes the potential applicability of the GPR metamodel-based S-O model for developing sustainable coastal groundwater management strategies, which can utilize accurate and efficient prediction of management strategy impacts on the saltwater intrusion (SI) process when the optimal management policy development is based on the trained metamodel predictions. Once implemented, the developed strategy can help in controlling SI in coastal aquifer systems.

Lin, Wenxian, and Armfield, S.W. (2020) Prandtl number scalings for unsteady natural convection boundary-layer flow on an evenly heated vertical plate in a homogeneous Pr > 1 fluid. Numerical Heat Transfer, Part A: Applications, 77 (6). pp. 619-631.
Scalings for the thicknesses of the thermal and velocity boundary layers, the plate temperature, and the maximum vertical velocity in a homogeneous Pr > 1 fluid are validated against numerical results for unsteady natural convection boundary-layer flow on an evenly heated vertical plate. Results have been obtained for Rayleigh number and Prandtl number and the scaling relations are shown to provide a good description of the flow for both the initial conduction dominated, one-dimensional, unsteady phase and the fully developed convection dominated, two-dimensional, steady phase of the flow. Scaling constants have been obtained for all relations.

Huang, Tao, Yuan, Xiaojun, Yuan, Jinhong, and Xiang, Wei (2020) Optimization of data exchange in 5G vehicle-to-infrastructure edge networks. IEEE Transactions on Vehicular Technology. (In Press)
In recent years, intelligent transportation systems are a vital part of the development of smart cities. In intelligent transportation systems, it is necessary for each vehicle to know the states of all other running vehicles within a range, depends on the road speed limit. The states include location, travelling direction, speed, and possibly other useful information. Knowing the states of surrounding vehicles is critical in high-risk locations, such as traffic intersections and roundabouts. The development of 5G and its technologies, such as massive multiple-input multiple-output antenna, enables a new communication model, termed vehicle-to-infrastructure edge network (V2IEN), to achieve the above communication goal. In this paper, we study the optimization of the data throughput of the proposed V2IENs in 5G with the Time Division Duplex scheme. We show that due to the nature of information flow in the proposed V2IENs, the uplink and downlink traffic loads are asymmetric. This asymmetric characteristic allows maximizing the degrees of freedom of the V2IENs by optimizing the time-slot resources for uplink and downlink transmission. In this work, we present the sum-DoF capacity of the V2IENs with proof. We demonstrate that a significant DoF gain is achieved for the V2IENs by carefully allocate the system transmission time resources. We further propose an iterative algorithm for network sum-rate maximization via the optimization of the vehicle and base station precoders. Numerical results demonstrate that a careful design of the precoders at the base station and at the vehicles can considerably improve the V2IENs performance.

Sivakugan, Siva, Ameratunga, Jay, and Das, Braja M. (2020) Site characterisation for residential slabs and footings - Australian practice. International Journal of Geotechnical Engineering, 14 (2). pp. 130-133.
Expansive soils, known as reactive soils in Australia, pose serious threat to low-rise buildings, roadworks and other infrastructure. Expansive soils are encountered in all capital cities. The purpose of this technical note is to summarise the Australian practice of site classification, especially when expansive soils are present. The expected vertical movement at the ground level due to seasonal changes in moisture content is used as the basis for site classification. This is computed on the basis of the depth within which the moisture changes are expected and the maximum suction expected at the ground level.

Farooq, Muhammad Umar, Mujtaba, Hassan, Farooq, Khalid, Sivakugan, Nagaratnam, and Das, Braja M. (2020) Evaluation of stability and erosion characteristics of soil embankment slope reinforced with different natural additives. Iranian Journal of Science and Technology, Transactions of Civil Engineering. (In Press)
The top soil layer in an embankment slope is susceptible to erosion, and especially during rainfall it is highly vulnerable, offering the least resistance against erosion and loses strength drastically. The work reported herein summarizes an experimental study on the effects of blending rice husk (RH) and sawdust (SD) in clayey soil in mitigating erosion potential and increasing shear strength parameters of clayey soil used in earthen embankment. For this purpose, several different soil mixes were prepared with either RH or SD. The RH content was increased from 0 to 21% by weight in 3% increments, and SD content was increased from 0 to 7% in 1% increments. Unconfined compression and unconsolidated undrained (UU) triaxial tests were carried out on remolded soil samples mixed with varying RH and SD contents to measure the unconfined compressive strength (UCS) and shear strength parameters (c and ϕ). It was observed that with addition of 15% of RH, the UCS value increased from 121 to 287 kPa, whereas UCS increased from 121 to 407 kPa with 5% addition of SD. The UU triaxial test results revealed that the cohesion of improved soil increased by 2 times and 3 times and its ϕ improved by about 6° and 9° with addition of 15% RH and 5% SD, respectively. Both type of test results suggested that the maximum possible strength increase was achieved by 15% dosage of RH and 5% of SD. Further, soil erosion tests were also carried out using an erosion measuring laboratory setup. These test results also suggested the same dosages of RH and SD in the soil giving the least erosion of the improved soil. The soil erosion rate decreased from 32% in case of untreated soil to about 15% and 12% at optimum content of RH and SD, respectively. Based on this study, the use of SD may be preferred as compared with RH in mitigating soil erosion for its higher erosion resistance and strength characteristics.

Zhou, L., Armfield, S.W., Williamson, N., Kirkpatrick, M.P., and Lin, W. (2020) Natural convection in a cavity with time-varying thermal forcing on a sidewall. International Journal of Heat and Mass Transfer, 150. 119234.
Transient natural convection flow is investigated in a two-dimensional square enclosure, subjected to periodic heating and cooling on one sidewall. The thermal forcing applied on the heated sidewall varies with time as a sine wave around a zero mean at a frequency f , with all other walls adiabatic. The time- varying heating/cooling produces an alternating direction vertical natural convection boundary layer that entrains fluid from the cavity interior and discharges it alternatively at the top and bottom of the cavity. The behaviour of the flow is governed by three characteristic time scales, the forcing period, 1/ f , the development time for the boundary layer and the filling time of the cavity. For low forcing frequency the filling time is less than the forcing period and the time average stratification S is well approximated by S ∼f 4 / 5 . For high forcing frequency the forcing period is smaller than the boundary layer development time and S ∼f −2 . The maximum S occurs in a transition region, between the low and high frequency ranges. The maximum value of S increases with increasing Rayleigh number, approaching S ∼= 1 . 0 for the highest values of Rayleigh number considered.

Li, Qiong, Gao, Wenfeng, Lin, Wenxian, Liu, Tao, Zhang, Yonggang, Ding, Xiang, Huang, Xiaoqiao, and Liu, Wuming (2020) Experiment and simulation study on convective heat transfer of all-glass evacuated tube solar collector. Renewable Energy, 152. pp. 1129-1139.
Solar collector with horizontal double-row all-glass evacuated tubes has been extensively implemented in the solar water heating system engineering. The temperature distribution and stratification of horizontal double-row all-glass evacuated tube collector with 24 evacuated tubes have been studied. Validation of instantaneous efficiency under different declination angle qm were studied by means of experiments. Moreover, numerical simulations are carried out for four different declination angle qm (0/2/4/6). The results showed that the declination angle qm has significant effect on energy conversion efficiency, flow patterns and stratification inside evacuated tubes. When qm > 0, with the declination angle increased, the instantaneous efficiency also increased, nevertheless, the temperature stratification weakened and the heat loss coefficient demonstrated no significant change. Declination angle 6 allowed to achieve significant higher temperatures, nevertheless, along with inactive area at the bottom of evacuated tubes appears. If declination angle qm < 0, inversion phenomenon appears. With the increase of |qm|, more heat is trapped in the sealed end of the evacuated tube, which is not conducive to the flow heat transfer in evacuated tube solar collector.

Almasi, Milad, Karimi, Gholamreza, Ranjbar, Mahnaz, and Rahimi Azghadi, Mostafa (2020) New analogue stop-learning control module using astrocyte for neuromorphic learning. IET Circuits, Devices & Systems, 14 (1). pp. 100-106.
Learning algorithms and devices are an essential part of neural networks and neuromorphic architectures. Astrocyte, as an important element in the learning of neural networks, is believed to play a key role in long-term synaptic plasticity and memory. In addition, recent experimental observations indicate that astrocytes are active elements in learning in complex networks. In this study, the authors propose a new analogue astrocyte circuit that consumes fewer numbers of transistors compared to its previous counterparts. The authors then use this astrocyte to design a novel analogue circuit to implement a stop-learning mechanism in a spike-based learning algorithm and present its neuromorphic very large scale integration (VLSI) simulations. Experimental results demonstrate that the designed circuit can precisely implement the learning mechanisms shown by previous studies implementing spike-based learning rules without astrocyte. The proposed circuit proposes the first analogue stop-learning control algorithm that uses astrocytes. It has been designed and simulated in Taiwan semiconductor manufacturing company (TSMC) 0.35 μm complementary metal-oxide semiconductor (CMOS) technology.

Asgari, Hajar, Mazloom-Nezhad Maybodi, Babak, Payvand, Melika, and Rahimi Azghadi, Mostafa (2020) Low-energy and fast spiking neural network for context-dependent learning on FPGA. IEEE Transactions on Circuits and Systems Part 2: express briefs. (In Press)
Supervised, unsupervised, and reinforcement learning (RL) mechanisms are known as the most powerful learning paradigms empowering neuromorphic systems. These systems typically take advantage of unsupervised learning because they can learn the distribution of sensory information. However, to perform a task, not only is it important to have sensory information, but also it is required to have information about the context in which the system is operating. In this sense, reinforcement learning is very powerful for interacting with the environment while performing a context-dependent task. The predominant motivation for this research is to present a digital architecture for a spiking neural network (SNN) model with RL capability suitable for learning a context-dependent task. The proposed architecture is composed of hardware-friendly leaky integrate-and-firing (LIF) neurons and spike timing dependent plasticity (STDP)-based synapses implemented on a field programmable gate array (FPGA). Hardware synthesis and physical implementations show that the resulting circuits can faithfully reproduce the outcome of a learning task previously performed in both animal experimentation and computational modelings. Compared to the state-of-the-art neuromorphic FPGA circuits with context-dependent learning capability, our circuit fires 10.7 times fewer spikes, which accelerates learning 15 times, while requiring 16 times less energy. This is a significant step in achieving fast and low-energy SNNs with context-dependent learning ability on FPGAs.

Rahimi Azghadi, Mostafa, Chen, Ying-Chen, Eshraghian, Jason K., Chen, Jia, Lin, Chih-Yang, Amirsoleimani, Amirali, Mehonic, Adnan, Kenyon, Anthony J., Fowler, Burt, Lee, Jack C., and Chang, Yao-Feng (2020) CMOS and memristive hardware for neuromorphic computing. Advanced Intelligent Systems. (In Press)
The ever-increasing processing power demands of digital computers cannot continue to be fulfilled indefinitely unless there is a paradigm shift in computing. Neuromorphic computing, which takes inspiration from the highly parallel, low power, high speed, and noise-tolerant computing capabilities of the brain, may provide such a shift. To that end, various aspects of the brain, from its basic building blocks, such as neurons and synapses, to its massively parallel in-memory computing networks have been being studied by the huge neuroscience community. Concurrently, many researchers from across academia and industry have been studying materials, devices, circuits, and systems, to implement some of the functions of networks of neurons and synapses to develop bio-inspired (neuromorphic) computing platforms.

Madanayaka, Thushara Asela, and Sivakugan, Nagaratnam (2020) Validity of the method of fragments for seepage analysis in circular cofferdams. Geotechnical and Geological Engineering, 38. pp. 1547-1565.
The method of fragments (MoF) is a simple solution method for confined seepage problems. MoF based seepage solutions have been proposed and validated in the literature on cofferdams analyzed in the 2D Cartesian plane (i.e., double-walled cofferdams). More recently, this method has been extended by the authors for determining the flow rate and exit hydraulic gradient for axisymmetric cases (circular cofferdams). The accuracy of the MoF solutions for circular cofferdams relies on the assumption that the equipotential surface along the cofferdam perimeter at the tip of the cut-off wall is vertical. Therefore, in the first part of the paper, the validity of this assumption and the effect of any deviation on the seepage solutions for circular cofferdams were studied. For that, series of circular cofferdam geometries were studied using numerical simulations, and then the seepage solutions (flow rate and exit hydraulic gradient values) obtained were compared with corresponding MoF solutions. It shows that the MoF solutions are conservative in all the cases and also the error is limited to 10% for most of the cases. In the second part of the paper, an attempt is made to simplify the MoF solutions, further developing expressions for the form factors of the two fragments and the exit hydraulic gradient without relying on the graphical solutions proposed by the authors. The equations presented herein enable the MoF to be implemented in spreadsheet and hence be used as an effective tool for parametric studies.

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