Recent Submissions

  • Numerical analysis of shock interaction with a spherical bubble

    Onwuegbu, Solomon; Yang, Zhiyin; University of Derby (AIP Publishing, 2022-02-11)
    Two-dimensional and three-dimensional computational fluid dynamics studies of a spherical bubble impacted by a supersonic shock wave (Mach 1.25) have been performed to fully understand the complex process involved in shock–bubble interaction (SBI). The unsteady Reynolds-averaged Navier–Stokes computational approach with a coupled level set and volume of fluid method has been employed in the present study. The predicted velocities of refracted wave, transmitted wave, upstream interface, downstream interface, jet, and vortex ring agree very well with the relevant available experimental data. The predicted non-dimensional bubble and vortex velocities are also in much better agreement with the experiment data than values computed from a simple model of shock-induced Rayleigh–Taylor instability (the Richtmyer–Meshkov instability). Comprehensive flow visualization has been presented and analyzed to elucidate the SBI process from the beginning of bubble compression (continuous reflection and refraction of the acoustic wave fronts as well as the location of the incident, refracted and transmitted waves at the bubble compression stage) up to the formation of vortex rings as well as the production and distribution of vorticity. Furthermore, it is demonstrated that turbulence is generated with some small flow structures formed and more intensive mixing, i.e., turbulent mixing of helium with air starts to develop at the later stage of SBI.
  • Hydrogeophysical Characterization of Fractured Aquifers for Groundwater Exploration in the Federal District of Brazil

    Hussain, Yawar; Campos, José Eloi Guimarães; Borges, Welitom Rodrigues; Uagoda, Rogério Elias Soares; Hamza, Omar; Havenith, Hans-Balder; University of Liege, 4000 Liege, Belgium; University of Brasilia, Brasilia 70910-900, Brazil; University of Derby (MDPI AG, 2022-02-28)
    The present study applies a geophysical approach to the Federal district of Brazil, a challenging hydrogeologic setting that requires improved investigation to enhance groundwater prospecting to meet the rising water demand. The geophysical characterization of a complex hard-rock aquifer sub-system was conducted using direct current (DC) electrical resistivity tomography (ERT) integrated with surface geological information. With a total of twenty-seven ERT profiles, the resistivity acquisition was carried out using a dipole-dipole array of electrodes with an inter-electrode spacing of 10 m. Based on resistivity ranges, the interpretation of the inverted resistivity values indicated a ground profile consisting of upper dry soil, saprolite, weathered, and fresh bedrock. Along with this layered subsurface stratigraphy, the approach allowed us to map the presence of significant hydrogeological features sharp contrasting anomalies that may suggest structural controls separating high-resistivity (≥7000 Ω m) and low-resistivity (<7000 Ω m) conducting zones in the uppermost 10 m of the ground. The assumed impacts of these features on groundwater development are discussed in light of the Brasilia aquifer settings
  • Creep-Fatigue Behaviours of Sn-Ag-Cu Solder Joints in Microelectronics Applications

    Depiver, Joshua Adeniyi; Sabuj, Mallik; Amalu, Emeka H; Lu, Yiling; University of Derby (Taylor and Francis, 2021)
    Electronic manufacturing is one of the dynamic industries in the world in terms of leading in technological advancements. At the heart of electronic assembly lies the 'soldering technology' and the 'solder joints' between electronic components and substrate. During the operation of electronic products, solder joints experience harsh environmental conditions in terms of cyclic change of temperature and vibration and exposure to moisture and chemicals. Due to the cyclic application of loads and higher operational temperature, solder joints fail primarily through creep and fatigue failures. This paper presents the creep-fatigue behaviours of solder joints in a ball grid array (BGA), soldered on a printed circuit board (PCB). Using finite element (FE) simulation, the solder joints were subjected to thermal cycling and isothermal ageing. Accelerated thermal cycling (ATC) was carried out using a temperate range from 40℃ to 150℃, and isothermal ageing was done at -40,25,75 and 150℃ temperatures for 45 days (64,800 mins). The solders studied are lead-based eutectic Sn63Pb37 and lead-free SAC305, SAC387, SAC396 and SAC405. The results were analysed using the failure criterion of equivalent stress, strain rate, deformation rate, and the solders' strain energy density. The SAC405 and SAC396 are found to possess the least stress magnitude, strain rate, deformation rate, and strain energy density damage than the lead-based eutectic Sn63Pb37 solder; they have the highest fatigue lives based on the damage mechanisms. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. Furthermore, it proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.
  • Empowering digital supply chain transformation by utilizing Industry 4.0, Smart Factories, Standards, Smart Contracts and Blockchains

    Takhar, Sukhraj; University of Derby (2022-01-20)
    Companies that place products onto the marketplace, whether they are internally manufactured or sourced from a supply chain, are often faced with ever increasing demands for data from a diverse set of stakeholders, requiring a multitude of different data reporting needs to be identified and requested from suppliers, ranging from: the identification of raw materials; number of products in WIP state within facilities; finished stock levels in storage; demand needs from customers; numerous what-if scenarios; exposure analysis; safe use and disposal instructions; through to obligatory reporting data under chemical regulation to identify the presence of any hazardous chemicals on finished products; through to the emerging Environmental, Social, and Governance data reporting needs in order to gain access to future sources of funding. Blockchains are often mistakenly viewed as being solely related to recording transactional data related to some form of electronic payment mechanism. Smart contracts enable contracts between buyers and suppliers to create contract terms in an electronic manner and processed in an efficient and automated manner. This paper contributes to existing literature by identifying a research gap in transforming the currently diverse manually intensive data collection tasks, via digital technologies such as supply chain collection of reporting tasks embedded into smart contracts, with digital data flows supporting IPC-CFX and IPC technical standards, recording data collection requests and responses in real-time within a blockchain, which is then verified by applicable supply chain actors, to ensure data consistency, accuracy and verification. The proposed design enables companies to address existing state supply chain data collection tasks using as structured framework, enabling appropriate risks to be identified and managed accordingly in a more timely and consistent manner. The design may then be expanded in a consistent manner as new supply chain reporting needs arise.
  • Estimation of total groundwater reserves and delineation of weathered/fault zones for aquifer potential: A case study from the Federal District of Brazil

    Hussain, Yawar; Borges, Welitom; Uagoda, Rogerio; Moura, Cristiane; Maciel, Susanne; Hamza, Omar; Havenith, Hans-Balder; Liège University; University of Derby; University of Brasilia (Walter de Gruyter GmbH, 2021-08-18)
    In the Federal District of Brazil, groundwater extraction is challenged by fractured aquifers with difficulty in identification of hydraulic traps and significant uncertainty in the estimation of recharge potential. This study aims to optimize the demarcation of new locations of tubular wells by the aid of geophysical investigation. In the first stage of this study, the total exploitable amount of groundwater were calculated from the information of the physical environment and the existing wells. Second, electrical resistivity tomography (ERT) method was carried out on the selected sites – based on their surficial characteristics. The possible hydraulic traps (where groundwater might exist) were identified from the inversion of the resistivity measured by the dipole–dipole array and from the delineation of the resultant conducting zones (including the weathered rocks and fractures). Using this approach, we predicted the position and number of tubular wells required and ranked them according to their potential productivity. The study provides a promising framework for investigating groundwater in fractured aquifers.
  • Cure mechanism and kinetic prediction of biobased glass/polyfurfuryl alcohol prepreg by model-free kinetics

    Odiyi, D.C.; Sharif, T.; Choudhry, R.S.; Mallik, S.; University of Derby (Elsevier BV, 2022-12-26)
    This paper explains the cure reaction mechanisms of a novel bio-based glass/Polyfurfuryl prepreg using an experimental and numerical approach. It suggests optimized parameters of rapid curing for isothermal curing conditions. Dynamic scanning calorimetry (DSC) under non-isothermal conditions was used to determine parameters for the two model-free kinetic methods Friedman and Ozawa Flynn Wall. The average activation energy (88.9 ± 4.9 kJ/mol) was found to be higher than that reported for neat resin in literature. The validated models were used to gain insight into reaction mechanisms and were used to predict the evolution of reaction time under isothermal conditions for the PFA prepreg. This suggested that the curing time can be reduced to half by rapidly heating and maintaining isothermal conditions at 160°C, which provides faster curing using hot-press. In addition, dynamic mechanical analysis (DMA) was carried out to compare the manufacturer recommended cure cycle with the rapid cycle suggested.
  • Mechanical Properties and Failure Mechanisms of Novel Resin-infused Thermoplastic and Conventional Thermoset 3D Fabric Composites

    Shah, Syed Zulfiqar Hussain; Megat-Yusoff, Puteri Sri Melor; Karuppanan, Saravanan; Choudhry, Rizwan Saeed; Ahmad, Faiz; Sajid, Zubair; Universiti Teknologi Petronas, Perak, Malaysia; University of Derby (Springer Science and Business Media LLC, 2021-10-16)
    This paper presents an extensive comparison of the mechanical properties and failure mechanisms of a recently developed thermoplastic (Elium ®) 3D fabric-reinforced composite (3D-FRC) with the conventional thermoset (epoxy) 3D-FRC. Experiments involved tensile tests, compression tests, V-notch shear tests, and short beam shear tests for specimens produced through the vacuum-assisted resin infusion process in each case. These tests were used for the determination of in-plane elastic constants, failure strengths and for investigating the failure mechanisms. A micro-mechanical model validated against these experiments was used to predict the remaining orthotropic elastic constants. This work enhances our understanding of the mechanics of infusible thermoplastic 3D-FRC as a new class of emerging materials and provides useful data which substantiates that this unconventional thermoplastic resin is also easier to recycle, uses similar manufacturing processes and can be a suitable replacement for conventional thermoset resins.
  • Shape optimisation of cold roll formed sections considering effects of cold working

    Qadir, Sangar; Nguyen, Van Bac; Hajirasouliha, Iman; Ceranic, Boris; Tracada, Eleni; English, Martin; University of Derby; University of Sheffield; Hadley Industries plc (Elsevier, 2021-11-06)
    The design development of new cold roll formed sections can lead to a significant reduction in material costs if the sections are optimised for strength performance considering the effect of shapes and change of material properties by cold working during the manufacturing process. In this paper, the buckling and ultimate strengths of cold roll formed channel and zed sections with intermediate stiffeners under distortional bending were studied using experimentally validated Finite Element (FE) models. The section strength was optimised using FE modelling and optimisation based on Design Of Experiments (DOE) and response surface methodology. A nonlinear FE model was first developed for a referenced section subject to four-point bending tests and the section’s dimensions and material properties were defined as geometric parameters using the DOE technique. A response surface was then used to determine the influences of the stiffeners’ location, shape, size, and cold working at the section corners and stiffener bends during the manufacturing process. A multi-objective genetic algorithm method was deployed to obtain optimal shapes for the sections with maximum buckling and ultimate strengths while keeping the same amount of material used. The results revealed that the ultimate bending moment capacities could be enhanced up to 17% and 25% for the channel and zed sections, respectively. Including the cold working effect had considerable enhancement in the ultimate moment capacities, with a maximum increase of 5%. The results of this study clearly demonstrated an efficient and effective approach to optimise design for strength performance of cold roll formed sections.
  • Mechanical Engineering Design, Learning from the Past to Design a Better Future

    Sole, Martin; Barber, Patrick; Turner, Ian; The University of Derby (Loughborough University, 2021-11-07)
    The economic importance of design, and design engineers to the success of a company has led to the exponential growth in the demand for qualified design engineers. To fill this demand, colleges and universities provide the best training available so that, after graduation these engineers will provide significant input from the first day of work. We live in a time known as industry 4.0 or the 4th Industrial Revolution, where computer power rules and takes on greater tasks, freeing up time for the design engineer to design more and more complex designs. Sometimes, it is good to stop, and take a breath to review our practices and remind ourselves of things we may have forgotten. It is true that we can design complex mechanisms and systems, in times past many of these would not be possible. But can we learn or be reminded of good practice by taking a journey through some of the design methods from the past. This paper will travel back to the 2nd century BC and look at cutting edge water pump design and the importance of a good literature review. It will highlight a serious gap in knowledge when comparing full-time and part-time students in our modern age. Airship design will be reviewed, the R100, R38 and R101 to remind us of the need to cross check design calculations. Looking at the beauty of Concorde design will remind us of the requirement in any design of good planning and regular meetings. This journey will finish by looking at the design process of the Boeing 777 commercial airliner, one of the first designs to use Computer Aided Design (CAD) and Computer Aided Manufacture (CAM). The use of Design Build Teams (DBT) with cross-disciplinary experts who can reside anywhere in the world will be considered. The reviewed historical examples may at first glance appear happen-stance but are in fact linked, and demonstrate a continuing growth in the ability, knowledge, complexity, and techniques of engineering design. This step back in time will remind teachers of some basic principles when teaching design to future design engineers. Designs have become more complex in this modern age, but it would be incorrect to say that complex design did not exist in times past. Before the internet, aircraft were built, global communication systems existed, men went to the moon.
  • Experimental investigation on the quasi-static crush performance of resin-infused thermoplastic 3D fibre-reinforced composites

    Shah, S. Z. H; Megat-Yusoff, P.S.M; Choudhry, R.S; Sajid, Zubair; Din, I.U; Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak, Malaysia; University of Derby; National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan (Elsevier, 2021-09-01)
    This paper presents the quasi-static crush performance of newer resin-infused thermoplastic 3D fibre reinforced composites (FRC) under axial load. The main objective is to make an assessment of the energy absorption capability of novel 3D composites for improved energy absorbing applications. Flat specimens of resin-infused thermoplastic (TP) and thermoset (TS) 3D composites with three trigger angles, i.e., 15°, 30° and 45° were tested under quasi-static crush loads. The thermoplastic 3D-FRC at 45° trigger angle demonstrated 31% higher specific energy absorption (SEA), and 17% higher average crushing stress. This improved performance is attributed to higher fragmentation failure mechanisms, which absorbed more energy. These results elucidate that the resin-infused thermoplastic composites are suitable for higher energy absorption and lightweight design for automotive and sports applications.
  • Multiscale damage modelling of 3D woven composites under static and impact loads

    Shah, S. Z. H; Megat-Yusoff, P.S.M; Karuppanan, S; Choudhry, R.S; Sajid, Z; Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak 32610, Malaysia; University of Derby (Elsevier, 2021-09-24)
    A multiscale progressive damage modelling methodology for 3-dimensional (3D) woven composites is presented. The proposed methodology is generic and can be implemented in most finite element software to create a digital twin for simulation of damage response. It uses 3D solid element (reduced integration) representation of the part for global analysis, while the local damage response, as well as matrix nonlinearity is modelled using a mesoscale constitutive unit-cell model of 3D woven composite consisting of idealised regions of polymer matrix and impregnated yarns. The idealised unit-cell model is defined based on realistic input from X-ray tomography of the 3D woven composite part and the micro-level constituent properties of the matrix and fibres. The damage model has been validated using quasi-static tensile/compression tests as well as dynamic drop-weight impact tests for both thermoset (epoxy) and thermoplastic (Elium) 3D woven composites. These simulations successfully demonstrate the accuracy and efficiency of the model for both 3D-textile composites.
  • Influence of Yawed Wind Flow on the Blade Forces/Bending Moments and Blade Elastic Torsion for an Axial-Flow Wind Turbine

    Ahmadi, Mohammad H. B.; Yang, Zhiyin; University of Derby (American Society of Mechanical Engineers, 2021-09-16)
    Effects of yawed incoming flow on wind turbine blades forces and root bending moments (RBMs) are not fully understood. To advance our current understanding, numerical studies of a small-scale three-bladed horizontal axis wind turbine at TSR = 6.7 with yaw angles of zero and 45° have been carried out to examine the variations of blade and rotor loading due to the yawed incoming flow. An approach combining Large Eddy Simulation (LES) with Actuator Line Modelling (ALM) has been employed in the present study. The predicted phase-averaged blade forces reveal that the blade tangential force, in-plane RBM and power coefficient are much more sensitive to the upstream streamwise velocity variations and are much more strongly affected than the blade axial force, out-of-plane RBM and thrust coefficient. It also shows that for yawed incoming flows the blade axial force to the blade tangential force ratio fluctuates significantly during one rotor revolution, resulting in large variations of the blade elastic torsion and that the total blade force (magnitude and direction) undergoes a non-linear change in the circumferential and radial directions, which will likely lead to the reduction in the turbine operational life significantly, especially for long lightweight blades of large size wind turbines.
  • Regulating Product Sustainability

    Takhar, Raj; Takhar, Sukhraj; University of Derby (The Parliamentary Office of Science and Technology, 2021-06-10)
    Interview, written review and feedback on UK government proposals on the future of regulating product for sustainability.
  • Transforming product labels using digital technologies to enable enhanced traceability and management of hazardous chemicals

    Takhar, Sukhraj; Liyanage, Kapila; University of Derby (Inderscience, 2021-06-08)
    Manufacturers that produce, distribute or market physical products are likely to be impacted by numerous chemical and product regulations. Manufacturers must identify chemical substances which appear within mixtures, materials, formulations, raw materials, components, assemblies and finished products. This results in a very manual and resource intensive process of collection of chemical substances in products data, where definitions arise from internal, industry standards, supplier and customer requirements and often sourced from multiple supply chain actors. This paper contributes to existing literature by identifying a research gap in transforming current manual state data collection tasks via the utilisation of digital technologies, leveraging real-time data collection using smart labels to identify chemicals contained within products. The proposed design enables manufacturers to identify the use of chemicals consumed in a automated manner and enabling appropriate risks to be identified and managed accordingly. The design can be further expanded in the proposed collaborative data sharing network.
  • Realignment of Product Stewardship towards Chemical Regulations, the Circular Economy and Corporate Social Responsibility – a Delphi Study

    Liyanage, Kapila; Takhar, Sukhraj; University of Derby (Sepuluh Nopember Institute of Technology (ITS), 2021-07)
    Chemical regulations exist to limit and control the amount of hazardous chemical substances being used by industry. Increasing awareness of diminishing natural resources, increasing pollution, and reducing the amounts of harmful waste, has led towards increasing societal and regulatory pressure on industry to change from the traditional closed-loop manufacturing towards the adoption of sustainable materials and open-loop manufacturing systems as part of the Circular Economy. Corporate Social Responsibility (CSR) extends the relationship between industry and society. Product Stewardship (PS) provides a platform for organizations to assess impacts to manufacturing systems ensuring adequate measures are in place to understand, control or limit any impact(s) from manufacturing and using products. The research question answered in this paper relates to understanding the impacts on PS. This paper has been written based on a literature review and Delphi study. The outcomes from this paper will attempt to outline a framework for PS to align with Chemical Regulations, the Circular Economy and CSR.
  • Mechanical Engineering Design, Does the Past Hold the key to the Future?

    Sole, Martin; Ian, Turner; Barber, Patrick; University of Derby (The Design Society, 2021)
    Industry design of a complex product has always required a cross-disciplinary team of experts. Is it possible to mimic these teams in academia when training the design engineers of the future, and what disciplinary skills will they possess? The exceptional collaboration potential provided by the internet means industry experts can work as a team, and at the same time, reside anywhere in the world. What are the capabilities of teamwork when the team members may never see each other for real? Though a physical prototype is sometimes required, most prototypes are designed and created in the virtual world using 3D modelling. The model can be tested, checked for accuracy, have materials applied, and be created parametrically which allows the products geometry to be reset to different sizes by the designer. Collaboration, effective communication and 3D modelling make it possible to design intricate and complex designs remotely. While we rightly congratulate ourselves on the complexity of modern design and how clever we have become, we must not lose sight of past achievements. Design has become more complex in this modern age, but it would be incorrect to say that complex design did not exist in times past. Before the internet, aircraft were built, global communication systems existed, men went to the moon. What can we learn, if anything, by looking at the methods used to design complex products in the past? How can we apply what we learnt from the past to the future?
  • Design Education - A Reversed Method to Fill and Information and Knowledge Gap Between Full-Time and Part-Time Students

    Sole, Martin; Barber, Patrick; Ian, Turner; University of Derby (The Design Society, 2021-08)
    Teachers in schools, tutors in colleges, and lecturers in universities are all required to have specific teaching qualifications. As part of the qualification, it is normal to study tried and tested pedological theories. Some examples are Bloom’s Taxonomy, Constructivism, and Experiential Learning. This paper identifies a gap in the information and knowledge required of student design engineers studying on a full-time course, when compared to part-time students. To redress this gap, it is suggested that no new theories are required but just a new method of applying an old theory, the application of Bloom’s Taxonomy in reverse alongside reverse engineering. An example of applying this method to a class of design engineers in their final year of a BEng (Hons) Mechanical Engineering is provided.
  • The effect of fine droplets on laminar propagation speed of a strained acetone-methane flame: Experiment and simulations

    Fan, Luming; Tian, Bo; Chong, Cheng Tung; Jaafar, Mohammad Nazri Mohd; Tanno, Kenji; McGrath, Dante; Oliveira, Pedro M.de; Rogg, Bernd; Hochgreb, Simone; University of Derby; et al. (Elsevier, 2021-07-31)
    In this study, we investigate the effect of the presence of fuel droplets, their size and concentration, on stretched laminar flame speeds. We consider premixed strained methane/air mixtures, with the addition of small acetone droplets, and compare the flame velocity field behaviour to that of the fully vaporized mixture. An impinging stagnation flame configuration is used, to which a narrowly distributed polydisperse mist of acetone droplets is added. Total acetone molar concentrations between 9% and 20% per mole of methane are used, corresponding to 18.6% and 41.4% of the total fuel energy. The Sauter Mean Diameter (SMD) of acetone droplets is varied from 1.0 to 4.7 μm by carefully tuning the air flow rate passing through an atomizer. The droplet size distribution is characterized by a Phase Doppler Anamometry (PDA) system at the outlet of the burner. The flame propagation speed is measured using Particle Image Velocimetry (PIV) for overall equivalence ratios ranging from 0.8 to 1.4 at various strain rates, and the result is compared with a reference case in which acetone was fully vaporized. Unlike the fully vaporized flame, a two-stage reaction flame structure is observed for all droplet cases: a blue premixed flame front followed by a reddish luminous zone. Comparison of the results between gas-only and droplet-laden cases shows that the mean reference burning velocity of the mixture is significantly enhanced when droplets are present under rich cases, whereas the opposite is true for stoichiometric and lean cases. The mean droplet size also changes the relationship between flame speed and strain rate, especially for rich cases. The result suggests that with typical conditions found in laminar strained flames, even for the finest droplets that may have been vaporized before reaching the flame front, the resulting inhomogeneities may lead the flame to behaves differently from the well-premixed gaseous counterpart. Simulations at similar conditions are performed using a two-phase counterflow flame model to compare with experimental data. Model results of reference velocities do not compare well with observations, and the possible reasons for this behaviour are discussed, including the difficulties in determining the pre-vaporization process and thus the boundary conditions, as well as the fidelity of the current point-source based 1D model.
  • Thermal Fatigue Life of Ball Grid Array (BGA) Solder Joints Made From Different Alloy Compositions

    Depiver, Joshua Adeniyi; Sabuj, Mallik; Amalu, Emeka H; University of Derby; Teeside University (Elsevier, 2021-04-27)
    As temperature cycling drives fatigue failure of solder joints in electronic modules, characterisation of the thermal fatigue response of different solder alloy formulations in BGA solder joints functioning in mission-critical systems has become crucial. Four different lead-free and one eutectic lead-based solder alloys in BGA solder joints are characterised against their thermal fatigue lives (TFLs) to predict their mean-time-to-failure for preventive maintenance advice. Five finite elements (FE) models of the assemblies of the BGAs with the different solder alloy compositions are created with SolidWorks. The models are subjected to standard IEC 60749-25 temperature cycling in ANSYS mechanical package environment. Plastic strain, shear strain, plastic shear strain, and accumulated creep energy density responses of the solder joints are obtained and inputted into established life prediction models – Coffin Manson, Engelmaier, Solomon and Syed – to determine the lives of the models. SAC405 joints have the highest predicted TFL of circa 13.2 years, while SAC387 joints have the least life of circa 1.4 years. The predicted lives are inversely proportional to the magnitude of the areas of stress-strain hysteresis loops of the BGA solder joints. The prediction models are significantly not consistent in predicted magnitudes of TFLs across the solder joints. With circa 838% variation in the magnitudes of TFL predicted for Sn63Pb37, the damage parameters used in the models played a critical role and justifies that a combination of several failure modes drives solder joints damage. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. It proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.
  • Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

    Hussain, Yawar; Uagoda, Rogerio; Borges, Welitom; Prado, Renato; Hamza, Omar; Cárdenas-Soto, Martín; Havenith, Hans-Balder; Dou, Jie; Clemson University, Clemson, SC 29634, USA; University of Brasilia, Brasilia 70910-900, Brazil; et al. (MDPI, 2020-10-12)
    Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low-Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline.

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