The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Agus P Sasmito - One of the best experts on this subject based on the ideXlab platform.
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development of conjugate reduced order models for selective artificial Ground Freezing thermal and computational analysis
Applied Thermal Engineering, 2021Co-Authors: Ahmad F Zueter, Mahmoud A Alzoubi, Agus P SasmitoAbstract:Abstract Selective artificial Ground Freezing (S-AGF) applications usually extend to very deep levels (more than 400 meters); numerical modeling of such large AGF applications encounters two main issues: (i) Predicting the variable heat extraction capacity along the freeze-pipe depth and (ii) the extremely long computational time. In this paper, we develop novel semi-conjugate reduced-order models that accurately predict heat extraction along the freeze-pipe while substantially reducing the computational time. In regards to the thermal modeling novelty, the freeze-pipe boundary condition of S-AGF is mathematically derived considering the development of the coolant flow temperature and boundary layer. As for the computational novelty, fast semi-conjugate reduced-order algorithms are developed for S-AGF, with the optional incorporation of analytical solutions and spatial correction. The models are validated against experimental data and verified with established fully-conjugate models. The thermal results demonstrate that the phase transition front profile of the frozen Ground is primarily shaped by the thermal development of the flow. On the other hand, the computational results reveal that the computational time of the reduced-order algorithms is decreased by more than 99%, as compared with the established models. In short, our proposed reduced-order models are proven to be reliable and computationally efficient, which shows potential for practical field application.
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artificial Ground Freezing a review of thermal and hydraulic aspects
Tunnelling and Underground Space Technology, 2020Co-Authors: Mahmoud A Alzoubi, Ferri Hassani, Sebastien Poncet, Agus P SasmitoAbstract:Abstract The artificial Ground Freezing (AGF) is one of the most popular Ground-support methods. Driven by its reliability, compatibility with a wide range of Ground types, and low impact on the environment, the AGF became one of the most favorable geotechnical-support methods in various mining, civil, and environmental projects. Over the last few decades, there has been a growing interest in the AGF. Several studies have been conducted to investigate the complex phenomena associated with the AGF process. This paper provides a comprehensive overview of related publications that discuss the thermal and hydraulic characteristics of the AGF. It reviews the most common types of AGF systems, their basic configurations, and their main applications. It also examines a series of analytical, numerical, and experimental analyses undertaken to assess and quantify the heat transfer and fluid flow during the AGF process. Throughout the literature review, one can observe the significant improvement of the problem formulation during the last decades. Previously, the multi-phase heat transfer was formulated by solving the conduction energy equation. This approach, however, has been advanced to another level of complexity by considering the convective Groundwater flow. Currently, there are two common approaches to model the heat transfer of AGF problem: (i) the apparent heat capacity formulation, (ii) and the enthalpy-porosity formulation. It is concluded that the subject of AGF has received a lot of attention in the last decade, especially in environmental and civil applications. However, the number of experimental or analytical studies is very limited. Thus, there is a vast opportunity for research and development of the AGF.
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thermal and hydraulic analysis of selective artificial Ground Freezing using air insulation experiment and modeling
Computers and Geotechnics, 2020Co-Authors: Ahmad F Zueter, Aurelien Nierouquette, Mahmoud A Alzoubi, Agus P SasmitoAbstract:Abstract In some artificial Ground Freezing (AGF) applications of civil or mining projects, only particular parts of the Ground need to be frozen. Selective artificial Ground Freezing (S-AGF) is an AGF technique where a specific portion of the freeze pipe is insulated, usually by an air gap, to prevent any undesirable Ground Freezing. In this study, a laboratory scale experimental setup that mimics actual S-AGF systems has been established. The experimental rig is built in a fully controlled environment and equipped with advanced instrumentation. Additionally, a mathematical model coupling the flow of the coolant, air, and porous Ground is developed by solving the conservation equations of mass, momentum, and energy. The mathematical model is then validated against the experimental measurements of the Ground and outlet coolant temperatures. Moreover, the natural convection inside the air gap is further validated at higher Rayleigh numbers with an experimental study from the literature. The results indicate that the energy consumption of AGF plants can be significantly reduced by applying the S-AGF concept, as compared to convectional AGF systems. Also, it is found that the optimum air gap thickness, L opt , relates to the cavity height, H, and Rayleigh number, Ra H , as L opt ~ 2 HRa H - 1 / 4 .
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on the concept of the Freezing on demand fod in artificial Ground Freezing for long term applications
International Journal of Heat and Mass Transfer, 2019Co-Authors: Mahmoud A Alzoubi, Aurelien Nierouquette, Ferri Hassani, Seyed Ali Ghoreishimadiseh, Agus P SasmitoAbstract:Abstract The continuous mode of operation of artificial Ground Freezing (AGF) systems in long-term applications requires intensive energy consumption, which leads to immense operating and maintenance costs not to mention a large carbon footprint. Therefore, a reliable technique is needed to reduce energy consumption whilst maintaining sufficient structural stability and safe operation. This paper introduces and demonstrates a novel concept of the Freezing-on-demand (FoD) by means of experiment and mathematical model. A fully controlled laboratory scale experiment is conceived and developed to assess the feasibility of the FoD concept. A three-dimensional mathematical model has been derived, validated, and utilized to simulate the AGF under three operating scenarios: (i) continuous mode, (ii) time-based FoD, and (iii) temperature-based FoD. Each scenario examines the effect of several designs and operating parameters on the Ground’s response and energy consumption. The results suggest that the concept of the FoD could significantly reduce energy consumption by up to 46%, as compared to the conventional counterpart which shows its potential for practical applications.
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heat transfer analysis in artificial Ground Freezing under high seepage validation and heatlines visualization
International Journal of Thermal Sciences, 2019Co-Authors: Mahmoud A Alzoubi, Ali Madiseh, Ferri Hassani, Agus P SasmitoAbstract:Abstract The primary goal of artificial Ground Freezing (AGF) system is to create a hydraulic barrier encircling working areas and stall Groundwater seepage. This goal is achieved once a consolidated frozen wall is developed between the freeze pipes. Groundwater flow, however, has an undesirable effect on the formation and the growth rate of the frozen body - high water flow could hamper, totally, the establishment of a merged frozen wall between two freeze pipes. Therefore, it is of great interest to evolve a reliable prediction of the transient response of the Ground structure toward the AGF process under high seepage flow conditions. This work interprets the multiphase heat transfer that accompanying the development of a frozen body between two freeze pipes with and without the presence of the Groundwater seepage. A mathematical model has been derived, validated, and implemented to simulate the effect of the coolant's temperature, the spacing between two freeze pipes, and the seepage temperature on the closure time and the shape of the frozen body. The results are presented in terms of temperature fields, phase-change interface, velocity-streamlines, and heatlines. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.
Mahmoud A Alzoubi - One of the best experts on this subject based on the ideXlab platform.
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development of conjugate reduced order models for selective artificial Ground Freezing thermal and computational analysis
Applied Thermal Engineering, 2021Co-Authors: Ahmad F Zueter, Mahmoud A Alzoubi, Agus P SasmitoAbstract:Abstract Selective artificial Ground Freezing (S-AGF) applications usually extend to very deep levels (more than 400 meters); numerical modeling of such large AGF applications encounters two main issues: (i) Predicting the variable heat extraction capacity along the freeze-pipe depth and (ii) the extremely long computational time. In this paper, we develop novel semi-conjugate reduced-order models that accurately predict heat extraction along the freeze-pipe while substantially reducing the computational time. In regards to the thermal modeling novelty, the freeze-pipe boundary condition of S-AGF is mathematically derived considering the development of the coolant flow temperature and boundary layer. As for the computational novelty, fast semi-conjugate reduced-order algorithms are developed for S-AGF, with the optional incorporation of analytical solutions and spatial correction. The models are validated against experimental data and verified with established fully-conjugate models. The thermal results demonstrate that the phase transition front profile of the frozen Ground is primarily shaped by the thermal development of the flow. On the other hand, the computational results reveal that the computational time of the reduced-order algorithms is decreased by more than 99%, as compared with the established models. In short, our proposed reduced-order models are proven to be reliable and computationally efficient, which shows potential for practical field application.
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artificial Ground Freezing a review of thermal and hydraulic aspects
Tunnelling and Underground Space Technology, 2020Co-Authors: Mahmoud A Alzoubi, Ferri Hassani, Sebastien Poncet, Agus P SasmitoAbstract:Abstract The artificial Ground Freezing (AGF) is one of the most popular Ground-support methods. Driven by its reliability, compatibility with a wide range of Ground types, and low impact on the environment, the AGF became one of the most favorable geotechnical-support methods in various mining, civil, and environmental projects. Over the last few decades, there has been a growing interest in the AGF. Several studies have been conducted to investigate the complex phenomena associated with the AGF process. This paper provides a comprehensive overview of related publications that discuss the thermal and hydraulic characteristics of the AGF. It reviews the most common types of AGF systems, their basic configurations, and their main applications. It also examines a series of analytical, numerical, and experimental analyses undertaken to assess and quantify the heat transfer and fluid flow during the AGF process. Throughout the literature review, one can observe the significant improvement of the problem formulation during the last decades. Previously, the multi-phase heat transfer was formulated by solving the conduction energy equation. This approach, however, has been advanced to another level of complexity by considering the convective Groundwater flow. Currently, there are two common approaches to model the heat transfer of AGF problem: (i) the apparent heat capacity formulation, (ii) and the enthalpy-porosity formulation. It is concluded that the subject of AGF has received a lot of attention in the last decade, especially in environmental and civil applications. However, the number of experimental or analytical studies is very limited. Thus, there is a vast opportunity for research and development of the AGF.
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thermal and hydraulic analysis of selective artificial Ground Freezing using air insulation experiment and modeling
Computers and Geotechnics, 2020Co-Authors: Ahmad F Zueter, Aurelien Nierouquette, Mahmoud A Alzoubi, Agus P SasmitoAbstract:Abstract In some artificial Ground Freezing (AGF) applications of civil or mining projects, only particular parts of the Ground need to be frozen. Selective artificial Ground Freezing (S-AGF) is an AGF technique where a specific portion of the freeze pipe is insulated, usually by an air gap, to prevent any undesirable Ground Freezing. In this study, a laboratory scale experimental setup that mimics actual S-AGF systems has been established. The experimental rig is built in a fully controlled environment and equipped with advanced instrumentation. Additionally, a mathematical model coupling the flow of the coolant, air, and porous Ground is developed by solving the conservation equations of mass, momentum, and energy. The mathematical model is then validated against the experimental measurements of the Ground and outlet coolant temperatures. Moreover, the natural convection inside the air gap is further validated at higher Rayleigh numbers with an experimental study from the literature. The results indicate that the energy consumption of AGF plants can be significantly reduced by applying the S-AGF concept, as compared to convectional AGF systems. Also, it is found that the optimum air gap thickness, L opt , relates to the cavity height, H, and Rayleigh number, Ra H , as L opt ~ 2 HRa H - 1 / 4 .
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on the concept of the Freezing on demand fod in artificial Ground Freezing for long term applications
International Journal of Heat and Mass Transfer, 2019Co-Authors: Mahmoud A Alzoubi, Aurelien Nierouquette, Ferri Hassani, Seyed Ali Ghoreishimadiseh, Agus P SasmitoAbstract:Abstract The continuous mode of operation of artificial Ground Freezing (AGF) systems in long-term applications requires intensive energy consumption, which leads to immense operating and maintenance costs not to mention a large carbon footprint. Therefore, a reliable technique is needed to reduce energy consumption whilst maintaining sufficient structural stability and safe operation. This paper introduces and demonstrates a novel concept of the Freezing-on-demand (FoD) by means of experiment and mathematical model. A fully controlled laboratory scale experiment is conceived and developed to assess the feasibility of the FoD concept. A three-dimensional mathematical model has been derived, validated, and utilized to simulate the AGF under three operating scenarios: (i) continuous mode, (ii) time-based FoD, and (iii) temperature-based FoD. Each scenario examines the effect of several designs and operating parameters on the Ground’s response and energy consumption. The results suggest that the concept of the FoD could significantly reduce energy consumption by up to 46%, as compared to the conventional counterpart which shows its potential for practical applications.
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heat transfer analysis in artificial Ground Freezing under high seepage validation and heatlines visualization
International Journal of Thermal Sciences, 2019Co-Authors: Mahmoud A Alzoubi, Ali Madiseh, Ferri Hassani, Agus P SasmitoAbstract:Abstract The primary goal of artificial Ground Freezing (AGF) system is to create a hydraulic barrier encircling working areas and stall Groundwater seepage. This goal is achieved once a consolidated frozen wall is developed between the freeze pipes. Groundwater flow, however, has an undesirable effect on the formation and the growth rate of the frozen body - high water flow could hamper, totally, the establishment of a merged frozen wall between two freeze pipes. Therefore, it is of great interest to evolve a reliable prediction of the transient response of the Ground structure toward the AGF process under high seepage flow conditions. This work interprets the multiphase heat transfer that accompanying the development of a frozen body between two freeze pipes with and without the presence of the Groundwater seepage. A mathematical model has been derived, validated, and implemented to simulate the effect of the coolant's temperature, the spacing between two freeze pipes, and the seepage temperature on the closure time and the shape of the frozen body. The results are presented in terms of temperature fields, phase-change interface, velocity-streamlines, and heatlines. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.
Ferri Hassani - One of the best experts on this subject based on the ideXlab platform.
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artificial Ground Freezing a review of thermal and hydraulic aspects
Tunnelling and Underground Space Technology, 2020Co-Authors: Mahmoud A Alzoubi, Ferri Hassani, Sebastien Poncet, Agus P SasmitoAbstract:Abstract The artificial Ground Freezing (AGF) is one of the most popular Ground-support methods. Driven by its reliability, compatibility with a wide range of Ground types, and low impact on the environment, the AGF became one of the most favorable geotechnical-support methods in various mining, civil, and environmental projects. Over the last few decades, there has been a growing interest in the AGF. Several studies have been conducted to investigate the complex phenomena associated with the AGF process. This paper provides a comprehensive overview of related publications that discuss the thermal and hydraulic characteristics of the AGF. It reviews the most common types of AGF systems, their basic configurations, and their main applications. It also examines a series of analytical, numerical, and experimental analyses undertaken to assess and quantify the heat transfer and fluid flow during the AGF process. Throughout the literature review, one can observe the significant improvement of the problem formulation during the last decades. Previously, the multi-phase heat transfer was formulated by solving the conduction energy equation. This approach, however, has been advanced to another level of complexity by considering the convective Groundwater flow. Currently, there are two common approaches to model the heat transfer of AGF problem: (i) the apparent heat capacity formulation, (ii) and the enthalpy-porosity formulation. It is concluded that the subject of AGF has received a lot of attention in the last decade, especially in environmental and civil applications. However, the number of experimental or analytical studies is very limited. Thus, there is a vast opportunity for research and development of the AGF.
-
on the concept of the Freezing on demand fod in artificial Ground Freezing for long term applications
International Journal of Heat and Mass Transfer, 2019Co-Authors: Mahmoud A Alzoubi, Aurelien Nierouquette, Ferri Hassani, Seyed Ali Ghoreishimadiseh, Agus P SasmitoAbstract:Abstract The continuous mode of operation of artificial Ground Freezing (AGF) systems in long-term applications requires intensive energy consumption, which leads to immense operating and maintenance costs not to mention a large carbon footprint. Therefore, a reliable technique is needed to reduce energy consumption whilst maintaining sufficient structural stability and safe operation. This paper introduces and demonstrates a novel concept of the Freezing-on-demand (FoD) by means of experiment and mathematical model. A fully controlled laboratory scale experiment is conceived and developed to assess the feasibility of the FoD concept. A three-dimensional mathematical model has been derived, validated, and utilized to simulate the AGF under three operating scenarios: (i) continuous mode, (ii) time-based FoD, and (iii) temperature-based FoD. Each scenario examines the effect of several designs and operating parameters on the Ground’s response and energy consumption. The results suggest that the concept of the FoD could significantly reduce energy consumption by up to 46%, as compared to the conventional counterpart which shows its potential for practical applications.
-
heat transfer analysis in artificial Ground Freezing under high seepage validation and heatlines visualization
International Journal of Thermal Sciences, 2019Co-Authors: Mahmoud A Alzoubi, Ali Madiseh, Ferri Hassani, Agus P SasmitoAbstract:Abstract The primary goal of artificial Ground Freezing (AGF) system is to create a hydraulic barrier encircling working areas and stall Groundwater seepage. This goal is achieved once a consolidated frozen wall is developed between the freeze pipes. Groundwater flow, however, has an undesirable effect on the formation and the growth rate of the frozen body - high water flow could hamper, totally, the establishment of a merged frozen wall between two freeze pipes. Therefore, it is of great interest to evolve a reliable prediction of the transient response of the Ground structure toward the AGF process under high seepage flow conditions. This work interprets the multiphase heat transfer that accompanying the development of a frozen body between two freeze pipes with and without the presence of the Groundwater seepage. A mathematical model has been derived, validated, and implemented to simulate the effect of the coolant's temperature, the spacing between two freeze pipes, and the seepage temperature on the closure time and the shape of the frozen body. The results are presented in terms of temperature fields, phase-change interface, velocity-streamlines, and heatlines. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.
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Freezing on demand fod an energy saving technique for artificial Ground Freezing
Energy Procedia, 2019Co-Authors: Mahmoud A Alzoubi, Agus P Sasmito, Ali Madiseh, Ferri HassaniAbstract:Abstract The artificial Ground Freezing (AGF) systems are typically designed to operate continuously for two main reasons: (i) to maintain a certain thickness of the frozen barrier which strengthens the Ground’s structure, and (ii) to stop Groundwater seepage and sustain a safe operating environment within the working area. This non-stop procedure, in contrast, leads to massive energy consumption. Therefore, it is crucial to introduce new techniques that reduce the energy consumption, while ensuring desired Ground structure and safe operation. This paper discusses the concept of Freezing on demand (FoD) in terms of experiment and model validation. We built a laboratory-scale AGF rig to quantify the Ground’s behavior towards the FoD concept. We also developed a three-dimensional, conjugate-heat-transfer, mathematical model that simulates the transient AGF process with FoD technique. The model’s framework has been extended into in-situ geometry to examine the influence of the spacing between two pipes on the energy saving during the FoD process. The results show that the spacing has an inverse relationship with the drop in the energy consumption during the FoD. Undoubtedly, FoD concept gave a substantial drop in the energy consumption which could lead to the development of an energy-efficient AGF system.
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intermittent Freezing concept for energy saving in artificial Ground Freezing systems
Energy Procedia, 2017Co-Authors: Mahmoud A Alzoubi, Agus P Sasmito, Ali Madiseh, Ferri HassaniAbstract:Abstract The artificial Ground Freezing (AGF) system is widely used in underGround mines, shaft sinking, civil, and tunneling applications for stabilization of underGround structures, and for hydraulic sealing. This system, however, incurs intensive energy consumption that requires careful consideration of the design and operating parameters. This paper aims to introduce and demonstrate a novel concept of intermittent AGF system with the ultimate goal to reduce energy consumption while ensuring desired structural stability and hydraulic sealing. A validated two-dimensional model that considers conservation of mass, momentum, and energy is utilized to simulate the transient heat transfer between the Freezing pipes and the porous soil structure. The results show that a significant reduction of up to 40% in the energy consumption per year can be achieved by implementing such concept whilst maintaining frozen body at desired level. Clearly, this concept shows potential for practical application – of course further improvement and optimization is required.
Ali Madiseh - One of the best experts on this subject based on the ideXlab platform.
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heat transfer analysis in artificial Ground Freezing under high seepage validation and heatlines visualization
International Journal of Thermal Sciences, 2019Co-Authors: Mahmoud A Alzoubi, Ali Madiseh, Ferri Hassani, Agus P SasmitoAbstract:Abstract The primary goal of artificial Ground Freezing (AGF) system is to create a hydraulic barrier encircling working areas and stall Groundwater seepage. This goal is achieved once a consolidated frozen wall is developed between the freeze pipes. Groundwater flow, however, has an undesirable effect on the formation and the growth rate of the frozen body - high water flow could hamper, totally, the establishment of a merged frozen wall between two freeze pipes. Therefore, it is of great interest to evolve a reliable prediction of the transient response of the Ground structure toward the AGF process under high seepage flow conditions. This work interprets the multiphase heat transfer that accompanying the development of a frozen body between two freeze pipes with and without the presence of the Groundwater seepage. A mathematical model has been derived, validated, and implemented to simulate the effect of the coolant's temperature, the spacing between two freeze pipes, and the seepage temperature on the closure time and the shape of the frozen body. The results are presented in terms of temperature fields, phase-change interface, velocity-streamlines, and heatlines. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.
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Freezing on demand fod an energy saving technique for artificial Ground Freezing
Energy Procedia, 2019Co-Authors: Mahmoud A Alzoubi, Agus P Sasmito, Ali Madiseh, Ferri HassaniAbstract:Abstract The artificial Ground Freezing (AGF) systems are typically designed to operate continuously for two main reasons: (i) to maintain a certain thickness of the frozen barrier which strengthens the Ground’s structure, and (ii) to stop Groundwater seepage and sustain a safe operating environment within the working area. This non-stop procedure, in contrast, leads to massive energy consumption. Therefore, it is crucial to introduce new techniques that reduce the energy consumption, while ensuring desired Ground structure and safe operation. This paper discusses the concept of Freezing on demand (FoD) in terms of experiment and model validation. We built a laboratory-scale AGF rig to quantify the Ground’s behavior towards the FoD concept. We also developed a three-dimensional, conjugate-heat-transfer, mathematical model that simulates the transient AGF process with FoD technique. The model’s framework has been extended into in-situ geometry to examine the influence of the spacing between two pipes on the energy saving during the FoD process. The results show that the spacing has an inverse relationship with the drop in the energy consumption during the FoD. Undoubtedly, FoD concept gave a substantial drop in the energy consumption which could lead to the development of an energy-efficient AGF system.
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intermittent Freezing concept for energy saving in artificial Ground Freezing systems
Energy Procedia, 2017Co-Authors: Mahmoud A Alzoubi, Agus P Sasmito, Ali Madiseh, Ferri HassaniAbstract:Abstract The artificial Ground Freezing (AGF) system is widely used in underGround mines, shaft sinking, civil, and tunneling applications for stabilization of underGround structures, and for hydraulic sealing. This system, however, incurs intensive energy consumption that requires careful consideration of the design and operating parameters. This paper aims to introduce and demonstrate a novel concept of intermittent AGF system with the ultimate goal to reduce energy consumption while ensuring desired structural stability and hydraulic sealing. A validated two-dimensional model that considers conservation of mass, momentum, and energy is utilized to simulate the transient heat transfer between the Freezing pipes and the porous soil structure. The results show that a significant reduction of up to 40% in the energy consumption per year can be achieved by implementing such concept whilst maintaining frozen body at desired level. Clearly, this concept shows potential for practical application – of course further improvement and optimization is required.
Ahmed Rouabhi - One of the best experts on this subject based on the ideXlab platform.
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thermo hydro mechanical modeling of artificial Ground Freezing taking into account the salinity of the saturating fluid
Computers and Geotechnics, 2020Co-Authors: Haffsa Tounsi, Ahmed Rouabhi, Emad JahangirAbstract:Abstract The modeling of Artificial Ground Freezing in geotechnical engineering applications has two main objectives, the first is the prediction of the extent of the frozen zone around the cooling sources (Thermo-Hydraulic models) and the second is the prediction of the Ground’s deformations and the site stability (Thermo-Hydro-Mechanical models). Reliable predictions require the consideration of unfavorable hydro-geological conditions such as high seepage velocities, Ground heterogeneity and saline Groundwater that may negatively influence the performance of AGF. The influence of the saturating fluid salinity on the THM behavior of the Ground during Freezing is the less documented point among the three and is therefore the subject of this paper. To this end, a fully coupled THM model considering the salinity effect has been derived. The formalism is completely thermodynamically consistent and introduces some simplifying assumptions, especially to describe phase change terms (capillary pressure and latent heat), in order to achieve a mathematical formulation that can be easily handled by computation software. Stress-free Freezing laboratory tests carried out on specimens initially fully saturated with sodium chloride solutions at three different concentrations allowed to validate the proposed approach and to highlight some key mechanisms associated with the phase change of saline-saturated porous media.
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Thermo-Hydro-Mechanical Modeling of Artificial Ground Freezing: Application in Mining Engineering
Rock Mechanics and Rock Engineering, 2019Co-Authors: H. Tounsi, Ahmed Rouabhi, Michel Tijani, Fabien GuérinAbstract:For decades, artificial Ground Freezing (AGF) has been used as a temporary soil stabilization and waterproofing technique in multiple geotechnical engineering applications. Experience gained from AGF experiments indicates that the pore water expansion during Freezing and the resulting pressure have the potential to induce Ground movements in adjacent nonfrozen areas. This process was investigated in this paper using a comprehensive set of in situ temperature and displacement monitoring data collected in the Cigar Lake underGround mine, Canada. The data set allowed to investigate the mechanical impact of Freezing on a mine tunnel and prompted the need to derive a fully coupled thermo-hydro-mechanical model to predict Ground temperature and displacements. Thermodynamically consistent, the model developed for this study is based on a macroscopic continuum approach and uses simplifying assumptions to overcome the computational difficulties associated with the modeling of complex mining environments over a long period of time. This model was used to perform three-dimensional finite-element simulations of the Ground Freezing and excavation activities in the Cigar Lake mine, showing good agreement with field measurements.
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modeling heat and mass transfer during Ground Freezing taking into account the salinity of the saturating fluid
International Journal of Heat and Mass Transfer, 2018Co-Authors: Ahmed Rouabhi, Emad Jahangir, H. TounsiAbstract:Abstract In geotechnical engineering applications, the modeling of artificial Ground Freezing is primarily aimed at predicting the extent of frozen zone around the cooling sources. This modeling could be more or less complex not only according to the material’s texture and the hydro-geological context but also to the salt concentration of the saturating fluid. Through a thermodynamically consistent framework, a fully coupled heat and mass transfer formulation considering the salinity effect was derived. This formulation was intended to capture the most relevant phenomena of Ground Freezing encountered in geotechnical applications. Particular attention was given to the phase change problem where appropriate simplifying assumptions were made in order to make the proposed methodology easier to apply in field applications. The proposed approach was validated by means of Freezing-thawing laboratory tests, carried out on specimens initially fully saturated with sodium chloride solutions at various concentrations. Good agreement was obtained between the measured and predicted results.
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Thermo-hydraulic modeling of artificial Ground Freezing: Application to an underGround mine in fractured sandstone
Computers and Geotechnics, 2016Co-Authors: Manon Vitel, Ahmed Rouabhi, Michel Tijani, Frédéric GuérinAbstract:The difficult geological conditions of underGround mines in permeable and fractured rocks require the use of Ground support and inflow management methods. Artificial Ground Freezing offers the opportunity to reduce the permeability of the Ground and to consolidate it. However, the establishment of this technique can be made complicated by two phenomenas: the strong Ground heterogeneity, which renders delicate an overall Freezing prediction, and the potential presence of high seepage-flow velocities, which may have a negative impact on Freezing progress. The present article presents a coupled use of the thermo-hydraulic model and the freeze-pipe Ground model presented in Vitel et al. (2016, 2015) with an application to the Cigar Lake underGround mine in Northern Saskatchewan, Canada. The first model allows the estimation of the temperature and pressure distribution in the Ground during Freezing while the second model simulates the heat transfer between a freeze pipe and the surrounding Ground, which is useful to determine the boundary conditions of the thermo-hydraulic model. First, the article restates the governing equations of both models. Then, after the validation of the numerical results with respect to field measurements, a joint use of the models is proposed, in particular to (i) predict the Ground temperature evolution, (ii) study the impacts of the geological conditions on the Freezing progress and (iii) optimize the Freezing system design.
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Modeling heat and mass transfer during Ground Freezing subjected to high seepage velocities
Computers and Geotechnics, 2016Co-Authors: Manon Vitel, Ahmed Rouabhi, Michel Tijani, Frédéric GuérinAbstract:Natural or induced Groundwater flow may negatively influence the performance of artificial Ground Freezing: high water flow velocities can prevent frozen conditions from developing. Reliable models that take into consideration hydraulic mechanisms are then needed to predict the Ground Freezing development. For forty years, numerous thermo-hydraulic coupled numerical models have been developed. Some of these models have been validated against experimental data but only one has been tested under high water flow velocity conditions. This paper describes a coupled thermo-hydraulic numerical model completely thermodynamically consistent and designed to simulate artificial Ground Freezing of a saturated and non-deformable porous medium under seepage flow conditions. On some points, less restrictive assumptions than the ones usually used in the literature are considered. As for the constant-porosity assumption, its validity is verified. The model appears to be well validated against analytical solutions and a three-dimensional Ground Freezing experiment under high seepage flow velocity conditions. It is used to highlight key thermo-hydraulic mechanisms associated with phase change in a porous medium.
