The Experts below are selected from a list of 26322 Experts worldwide ranked by ideXlab platform
Long Jin - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical analyses of the thermo mechanical stability of an Embankment with shady and sunny slopes in a permafrost region
Applied Thermal Engineering, 2017Co-Authors: Mingyi Zhang, Wansheng Pei, Long JinAbstract:Abstract The hydro-thermo-mechanical state is important for Embankments in permafrost regions, especially for the Embankments with shady and sunny slopes. It is difficult to determine the state because the complex hydro-thermo-mechanical interaction usually occurs within the Embankments during freezing-thawing processes. To explore the thermo-mechanical stability of Embankments in permafrost regions, an in-situ experiment of highway with asphalt pavement was performed firstly. Based on the observed results, a mathematical model was developed to describe the hydro-thermo-mechanical process. Subsequently, the model was validated by the observed data. Finally, the long-term stability of the Embankment was analyzed and predicted with a climate warming rate of 0.052 °C/a. The results show that, (1) the asphalt pavement heat absorption effect and shady-sunny slope effect reduce the stability of the Embankment; (2) the deformation of the Embankment demonstrates the periodic freezing-thawing fluctuation and the long-term creep settlement characteristics; (3) the settlement is mainly caused by the freezing-thawing behavior of the active layer, the moving down of the permafrost table, and the warming of permafrost; (4) the shady-sunny slope effect induces the uneven settlement, and the settlement difference increases with operation time. The study will be helpful for the design and maintenance of Embankments in permafrost regions.
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damage analysis of the characteristics and development process of thermosyphon Embankment along the qinghai tibet highway
Cold Regions Science and Technology, 2017Co-Authors: Shuangjie Wang, Long Jin, Hui Peng, Jianbing ChenAbstract:Abstract To analyse the damage characteristics of thermosyphon Embankments in a permafrost region, the Qingshui River section along the Qinghai-Tibet Highway (QTH) was used as a case study in which a field investigation and drilling were performed. The field soils were sampled, and their water content, dry density and compaction degree were tested in the laboratory. Based on the measured temperature data of the thermosyphon Embankment, damage characteristics and possible associated causes were analysed. The major damage found in thermosyphon Embankments was a longitudinal crack, which developed 1.0 to 2.0 m away from the thermosyphon. In partial sections, waves and other damage also occurred. The damage was primarily attributed to the non-uniform temperature distribution, which resulted in a non-uniform distribution of the mechanical properties of the Embankment filling. Under a heavy traffic load, stress concentration phenomena occurred at the freezing-thawing interface that gradually developed into a longitudinal crack with increased highway operation. The Embankment damage history, rainfall seepage, ponding near the Embankment and freezing-thawing cycles further accelerated the development of damage along the thermosyphon Embankments. According to the characteristics and causes of thermosyphon Embankment damage, precisely computing the cooling efficiency of thermosyphon in the design stage is necessary to prevent freezing-thawing interface waves resulting from excessive cooling effectiveness, to reduce thermal erosion from ponding near the Embankment by improving Embankment drainage systems, and to set necessary structural measures at thermosyphon Embankments that can improve their strength.
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Thermo-mechanical stability analysis of cooling Embankment with crushed-rock interlayer on a sloping ground in permafrost regions
Applied Thermal Engineering, 2017Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long JinAbstract:Abstract Some Embankments of highways are inevitably built on slopes in permafrost regions. It is usually difficult to ensure the stability of the Embankments on sloping ground because of the asymmetric geotemperature and stress distribution. The crushed-rock layer is often layed in the slope areas to control the geotemperature. Cooling performance is focused to evaluate the thermal stability of crushed-rock Embankment, but the mechanics are poorly concerned. This study developed a thermo-mechanical model to evaluate the influence of the cooling effect of crushed-rock layer on the mechanical state of Embankment on sloping ground. Two Embankments are taken as examples according to the engineering practice in permafrost regions on the Qinghai-Tibet Plateau, i.e., the unprotected Embankment and the crushed-rock interlayer Embankment. To analyze the stability of sloping Embankments, the geotemperature, principal strain, deformation and safety factor in four typical seasons are simulated during operations. Numerical results indicate that the crushed-rock interlayer can effectively cool the sloping Embankment and its foundation. Meanwhile, the cooling effect of the porous layer can reduce the uneven settlements to improve the safety reverse of the Embankment. This study can also provide scientific basis and reference for the design of similar engineering structures in permafrost regions.
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thermal stability analysis of crushed rock Embankments on a slope in permafrost regions
Cold Regions Science and Technology, 2014Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long Jin, Jon HarborAbstract:Abstract Highways/railways often pass across slope areas and their Embankments are often built on the slopes in permafrost regions. It is difficult to ensure the thermal stability of the Embankments at the slopes due to the effect of slopes. To protect the underlying permafrost, the crushed-rock Embankments are often used in the slope areas. Therefore, it is very necessary to explore the thermal state of crushed-rock Embankments located on the slopes. In this study, we studied numerically the temperature characteristics of three kinds of crushed-rock Embankments located on a slope under global warming, i.e. crushed-rock interlay Embankment, crushed-rock interlayer-revetment Embankment and crushed-rock base Embankment. Numerical results indicate that the crushed-rock interlayer Embankment and the crushed-rock interlayer-revetment Embankment, located on a slope with a ratio of 1:3.73 (about 15° from the horizontal), cannot effectively eliminate the negative effect of climate warming and construction-induced warming, and the effect of slope is still obvious on the thermal stability of permafrost under the crushed-rock interlayer Embankment. However, the crushed-rock base Embankment can significantly reduce the temperature of underlying permafrost and keep the underlying permafrost table stable for a long term; furthermore, the ground temperatures under the long side slope are far lower than those under the short side slope, and this will be more advantageous to control the slide of the Embankment located on a slope and increase its stability. We also find that the three kinds of Embankments cannot all remove the thermal effects of construction from themselves in a short term. Generally speaking, the crushed-rock base Embankment structure can be very advantageous to the thermal stability of the Embankment on a slope.
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the thermal budget evaluation of the two phase closed thermosyphon Embankment of the qinghai tibet highway in permafrost regions
Cold Regions Science and Technology, 2014Co-Authors: Long Jin, Jianbing Peng, Yuanhong Dong, Zhiyun LiuAbstract:Abstract The two-phase closed thermosyphon (TPCT) is a passive high-performance thermal transfer device that can efficiently decrease the ground temperature. However, only a few studies focus on the quantization of working efficiency of thermosyphons. Thus, in this study, based on data obtained from an experimental TPCT Embankment on the Qinghai–Tibet Highway from 2004 to 2012, the ground temperature fields of the TPCT Embankment were obtained, and the horizontal and vertical ground temperature characteristics were analysed. The results showed that the TPCT Embankment exhibited better thermal stability than that of a traditional Embankment. The artificial permafrost table was elevated to or maintained at the original natural level due to the cooling effect of the TPCT. To quantitatively analyse the cooling effect of the TPCT Embankment, a thermal budget evaluation method is proposed. The calculated results revealed the dynamic working state of the thermosyphon during its service period. The annual average energy of the TPCT transferred in a year was generally determined to be between 1500 MJ and 2000 MJ. The results of this study could provide a method to evaluate the TPCT Embankments and provide technological support in designing the TPCT Embankments in permafrost regions.
Mingyi Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical analyses of the thermo mechanical stability of an Embankment with shady and sunny slopes in a permafrost region
Applied Thermal Engineering, 2017Co-Authors: Mingyi Zhang, Wansheng Pei, Long JinAbstract:Abstract The hydro-thermo-mechanical state is important for Embankments in permafrost regions, especially for the Embankments with shady and sunny slopes. It is difficult to determine the state because the complex hydro-thermo-mechanical interaction usually occurs within the Embankments during freezing-thawing processes. To explore the thermo-mechanical stability of Embankments in permafrost regions, an in-situ experiment of highway with asphalt pavement was performed firstly. Based on the observed results, a mathematical model was developed to describe the hydro-thermo-mechanical process. Subsequently, the model was validated by the observed data. Finally, the long-term stability of the Embankment was analyzed and predicted with a climate warming rate of 0.052 °C/a. The results show that, (1) the asphalt pavement heat absorption effect and shady-sunny slope effect reduce the stability of the Embankment; (2) the deformation of the Embankment demonstrates the periodic freezing-thawing fluctuation and the long-term creep settlement characteristics; (3) the settlement is mainly caused by the freezing-thawing behavior of the active layer, the moving down of the permafrost table, and the warming of permafrost; (4) the shady-sunny slope effect induces the uneven settlement, and the settlement difference increases with operation time. The study will be helpful for the design and maintenance of Embankments in permafrost regions.
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Thermo-mechanical stability analysis of cooling Embankment with crushed-rock interlayer on a sloping ground in permafrost regions
Applied Thermal Engineering, 2017Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long JinAbstract:Abstract Some Embankments of highways are inevitably built on slopes in permafrost regions. It is usually difficult to ensure the stability of the Embankments on sloping ground because of the asymmetric geotemperature and stress distribution. The crushed-rock layer is often layed in the slope areas to control the geotemperature. Cooling performance is focused to evaluate the thermal stability of crushed-rock Embankment, but the mechanics are poorly concerned. This study developed a thermo-mechanical model to evaluate the influence of the cooling effect of crushed-rock layer on the mechanical state of Embankment on sloping ground. Two Embankments are taken as examples according to the engineering practice in permafrost regions on the Qinghai-Tibet Plateau, i.e., the unprotected Embankment and the crushed-rock interlayer Embankment. To analyze the stability of sloping Embankments, the geotemperature, principal strain, deformation and safety factor in four typical seasons are simulated during operations. Numerical results indicate that the crushed-rock interlayer can effectively cool the sloping Embankment and its foundation. Meanwhile, the cooling effect of the porous layer can reduce the uneven settlements to improve the safety reverse of the Embankment. This study can also provide scientific basis and reference for the design of similar engineering structures in permafrost regions.
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a full scale field experiment to evaluate the cooling performance of a novel composite Embankment in permafrost regions
International Journal of Heat and Mass Transfer, 2016Co-Authors: Mingyi Zhang, Wansheng Pei, Yuanming Lai, Tao Zhao, Jianming ZhangAbstract:Abstract High-grade highways designed for large traffic volumes need wider Embankments than railways and low-grade highways. In permafrost regions, a wide and dark-colored asphalt pavement surface of high-grade highways may destabilize underlying permafrost if the Embankment is insufficiently cooled, especially under a warming climate. However, the Embankments with single commonly cooling technique, e.g. two-phase closed thermosyphon (TPCT) Embankment and crushed-rock Embankment cannot satisfy the cooling requirement of high-grade highways because of their limited cooling capacities. Here, we use a full-scale field experiment of a separated high-grade highway with double lanes each direction at Beiluhe in the Qinghai-Tibet Plateau to investigate the thermal characteristics of a novel composite Embankment combined with L-shaped TPCTs, crushed-rock revetments and insulation, as well as an unprotected Embankment (as a control). Experimental results indicate that the composite Embankment can effectively cool the underlying permafrost and raise the permafrost table under the separated high-grade highway with a wide and dark-colored pavement, whereas the unprotected Embankment cannot. This composite Embankment should be considered for application to separated high-grade highways with double lanes each direction in permafrost regions, such as the planned Qinghai-Tibet Expressway.
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evaluating the cooling performance of crushed rock interlayer Embankments with unperforated and perforated ventilation ducts in permafrost regions
Energy, 2015Co-Authors: Mingyi Zhang, Xiyin Zhang, Wansheng Pei, Yuanming LaiAbstract:The crushed-rock interlayer Embankment with ventilation ducts has been advocated to stabilize the permafrost stratum under expressways in permafrost regions. This Embankment must render better cooling effect than railway Embankments because the expressway surface is wider and hotter. To this purpose, the walls of the ventilation ducts need to be perforated. This study evaluates the cooling performance of the rushed-rock interlayer Embankments with unperforated and perforated ventilation ducts along an expressway in permafrost regions of the Qinghai-Tibet Plateau. A three-dimensional numerical model is developed based on heat and mass transfer theories. The model includes the coupled heat transfer between air and ventilation duct wall, the air convective heat transfer in crushed-rock layer, and the heat conduction with phase change in soil layers. The numerical results indicate that if the ventilation ducts are perforated and embedded at the top of the crushed-rock interlayer, the cooling effect of the Embankment can be greatly enhanced. A good cooling performance can still be achieved even if the centerline spacing of the perforated ventilation ducts is enlarged to 4 m to facilitate the construction. The crushed-rock interlayer Embankment with perforated ventilation ducts is a better candidate structure for expressways in permafrost regions of the Qinghai-Tibet Plateau.
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thermal stability analysis of crushed rock Embankments on a slope in permafrost regions
Cold Regions Science and Technology, 2014Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long Jin, Jon HarborAbstract:Abstract Highways/railways often pass across slope areas and their Embankments are often built on the slopes in permafrost regions. It is difficult to ensure the thermal stability of the Embankments at the slopes due to the effect of slopes. To protect the underlying permafrost, the crushed-rock Embankments are often used in the slope areas. Therefore, it is very necessary to explore the thermal state of crushed-rock Embankments located on the slopes. In this study, we studied numerically the temperature characteristics of three kinds of crushed-rock Embankments located on a slope under global warming, i.e. crushed-rock interlay Embankment, crushed-rock interlayer-revetment Embankment and crushed-rock base Embankment. Numerical results indicate that the crushed-rock interlayer Embankment and the crushed-rock interlayer-revetment Embankment, located on a slope with a ratio of 1:3.73 (about 15° from the horizontal), cannot effectively eliminate the negative effect of climate warming and construction-induced warming, and the effect of slope is still obvious on the thermal stability of permafrost under the crushed-rock interlayer Embankment. However, the crushed-rock base Embankment can significantly reduce the temperature of underlying permafrost and keep the underlying permafrost table stable for a long term; furthermore, the ground temperatures under the long side slope are far lower than those under the short side slope, and this will be more advantageous to control the slide of the Embankment located on a slope and increase its stability. We also find that the three kinds of Embankments cannot all remove the thermal effects of construction from themselves in a short term. Generally speaking, the crushed-rock base Embankment structure can be very advantageous to the thermal stability of the Embankment on a slope.
Wansheng Pei - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical analyses of the thermo mechanical stability of an Embankment with shady and sunny slopes in a permafrost region
Applied Thermal Engineering, 2017Co-Authors: Mingyi Zhang, Wansheng Pei, Long JinAbstract:Abstract The hydro-thermo-mechanical state is important for Embankments in permafrost regions, especially for the Embankments with shady and sunny slopes. It is difficult to determine the state because the complex hydro-thermo-mechanical interaction usually occurs within the Embankments during freezing-thawing processes. To explore the thermo-mechanical stability of Embankments in permafrost regions, an in-situ experiment of highway with asphalt pavement was performed firstly. Based on the observed results, a mathematical model was developed to describe the hydro-thermo-mechanical process. Subsequently, the model was validated by the observed data. Finally, the long-term stability of the Embankment was analyzed and predicted with a climate warming rate of 0.052 °C/a. The results show that, (1) the asphalt pavement heat absorption effect and shady-sunny slope effect reduce the stability of the Embankment; (2) the deformation of the Embankment demonstrates the periodic freezing-thawing fluctuation and the long-term creep settlement characteristics; (3) the settlement is mainly caused by the freezing-thawing behavior of the active layer, the moving down of the permafrost table, and the warming of permafrost; (4) the shady-sunny slope effect induces the uneven settlement, and the settlement difference increases with operation time. The study will be helpful for the design and maintenance of Embankments in permafrost regions.
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Thermo-mechanical stability analysis of cooling Embankment with crushed-rock interlayer on a sloping ground in permafrost regions
Applied Thermal Engineering, 2017Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long JinAbstract:Abstract Some Embankments of highways are inevitably built on slopes in permafrost regions. It is usually difficult to ensure the stability of the Embankments on sloping ground because of the asymmetric geotemperature and stress distribution. The crushed-rock layer is often layed in the slope areas to control the geotemperature. Cooling performance is focused to evaluate the thermal stability of crushed-rock Embankment, but the mechanics are poorly concerned. This study developed a thermo-mechanical model to evaluate the influence of the cooling effect of crushed-rock layer on the mechanical state of Embankment on sloping ground. Two Embankments are taken as examples according to the engineering practice in permafrost regions on the Qinghai-Tibet Plateau, i.e., the unprotected Embankment and the crushed-rock interlayer Embankment. To analyze the stability of sloping Embankments, the geotemperature, principal strain, deformation and safety factor in four typical seasons are simulated during operations. Numerical results indicate that the crushed-rock interlayer can effectively cool the sloping Embankment and its foundation. Meanwhile, the cooling effect of the porous layer can reduce the uneven settlements to improve the safety reverse of the Embankment. This study can also provide scientific basis and reference for the design of similar engineering structures in permafrost regions.
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a full scale field experiment to evaluate the cooling performance of a novel composite Embankment in permafrost regions
International Journal of Heat and Mass Transfer, 2016Co-Authors: Mingyi Zhang, Wansheng Pei, Yuanming Lai, Tao Zhao, Jianming ZhangAbstract:Abstract High-grade highways designed for large traffic volumes need wider Embankments than railways and low-grade highways. In permafrost regions, a wide and dark-colored asphalt pavement surface of high-grade highways may destabilize underlying permafrost if the Embankment is insufficiently cooled, especially under a warming climate. However, the Embankments with single commonly cooling technique, e.g. two-phase closed thermosyphon (TPCT) Embankment and crushed-rock Embankment cannot satisfy the cooling requirement of high-grade highways because of their limited cooling capacities. Here, we use a full-scale field experiment of a separated high-grade highway with double lanes each direction at Beiluhe in the Qinghai-Tibet Plateau to investigate the thermal characteristics of a novel composite Embankment combined with L-shaped TPCTs, crushed-rock revetments and insulation, as well as an unprotected Embankment (as a control). Experimental results indicate that the composite Embankment can effectively cool the underlying permafrost and raise the permafrost table under the separated high-grade highway with a wide and dark-colored pavement, whereas the unprotected Embankment cannot. This composite Embankment should be considered for application to separated high-grade highways with double lanes each direction in permafrost regions, such as the planned Qinghai-Tibet Expressway.
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evaluating the cooling performance of crushed rock interlayer Embankments with unperforated and perforated ventilation ducts in permafrost regions
Energy, 2015Co-Authors: Mingyi Zhang, Xiyin Zhang, Wansheng Pei, Yuanming LaiAbstract:The crushed-rock interlayer Embankment with ventilation ducts has been advocated to stabilize the permafrost stratum under expressways in permafrost regions. This Embankment must render better cooling effect than railway Embankments because the expressway surface is wider and hotter. To this purpose, the walls of the ventilation ducts need to be perforated. This study evaluates the cooling performance of the rushed-rock interlayer Embankments with unperforated and perforated ventilation ducts along an expressway in permafrost regions of the Qinghai-Tibet Plateau. A three-dimensional numerical model is developed based on heat and mass transfer theories. The model includes the coupled heat transfer between air and ventilation duct wall, the air convective heat transfer in crushed-rock layer, and the heat conduction with phase change in soil layers. The numerical results indicate that if the ventilation ducts are perforated and embedded at the top of the crushed-rock interlayer, the cooling effect of the Embankment can be greatly enhanced. A good cooling performance can still be achieved even if the centerline spacing of the perforated ventilation ducts is enlarged to 4 m to facilitate the construction. The crushed-rock interlayer Embankment with perforated ventilation ducts is a better candidate structure for expressways in permafrost regions of the Qinghai-Tibet Plateau.
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thermal stability analysis of crushed rock Embankments on a slope in permafrost regions
Cold Regions Science and Technology, 2014Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long Jin, Jon HarborAbstract:Abstract Highways/railways often pass across slope areas and their Embankments are often built on the slopes in permafrost regions. It is difficult to ensure the thermal stability of the Embankments at the slopes due to the effect of slopes. To protect the underlying permafrost, the crushed-rock Embankments are often used in the slope areas. Therefore, it is very necessary to explore the thermal state of crushed-rock Embankments located on the slopes. In this study, we studied numerically the temperature characteristics of three kinds of crushed-rock Embankments located on a slope under global warming, i.e. crushed-rock interlay Embankment, crushed-rock interlayer-revetment Embankment and crushed-rock base Embankment. Numerical results indicate that the crushed-rock interlayer Embankment and the crushed-rock interlayer-revetment Embankment, located on a slope with a ratio of 1:3.73 (about 15° from the horizontal), cannot effectively eliminate the negative effect of climate warming and construction-induced warming, and the effect of slope is still obvious on the thermal stability of permafrost under the crushed-rock interlayer Embankment. However, the crushed-rock base Embankment can significantly reduce the temperature of underlying permafrost and keep the underlying permafrost table stable for a long term; furthermore, the ground temperatures under the long side slope are far lower than those under the short side slope, and this will be more advantageous to control the slide of the Embankment located on a slope and increase its stability. We also find that the three kinds of Embankments cannot all remove the thermal effects of construction from themselves in a short term. Generally speaking, the crushed-rock base Embankment structure can be very advantageous to the thermal stability of the Embankment on a slope.
Yuanming Lai - One of the best experts on this subject based on the ideXlab platform.
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Thermo-mechanical stability analysis of cooling Embankment with crushed-rock interlayer on a sloping ground in permafrost regions
Applied Thermal Engineering, 2017Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long JinAbstract:Abstract Some Embankments of highways are inevitably built on slopes in permafrost regions. It is usually difficult to ensure the stability of the Embankments on sloping ground because of the asymmetric geotemperature and stress distribution. The crushed-rock layer is often layed in the slope areas to control the geotemperature. Cooling performance is focused to evaluate the thermal stability of crushed-rock Embankment, but the mechanics are poorly concerned. This study developed a thermo-mechanical model to evaluate the influence of the cooling effect of crushed-rock layer on the mechanical state of Embankment on sloping ground. Two Embankments are taken as examples according to the engineering practice in permafrost regions on the Qinghai-Tibet Plateau, i.e., the unprotected Embankment and the crushed-rock interlayer Embankment. To analyze the stability of sloping Embankments, the geotemperature, principal strain, deformation and safety factor in four typical seasons are simulated during operations. Numerical results indicate that the crushed-rock interlayer can effectively cool the sloping Embankment and its foundation. Meanwhile, the cooling effect of the porous layer can reduce the uneven settlements to improve the safety reverse of the Embankment. This study can also provide scientific basis and reference for the design of similar engineering structures in permafrost regions.
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a full scale field experiment to evaluate the cooling performance of a novel composite Embankment in permafrost regions
International Journal of Heat and Mass Transfer, 2016Co-Authors: Mingyi Zhang, Wansheng Pei, Yuanming Lai, Tao Zhao, Jianming ZhangAbstract:Abstract High-grade highways designed for large traffic volumes need wider Embankments than railways and low-grade highways. In permafrost regions, a wide and dark-colored asphalt pavement surface of high-grade highways may destabilize underlying permafrost if the Embankment is insufficiently cooled, especially under a warming climate. However, the Embankments with single commonly cooling technique, e.g. two-phase closed thermosyphon (TPCT) Embankment and crushed-rock Embankment cannot satisfy the cooling requirement of high-grade highways because of their limited cooling capacities. Here, we use a full-scale field experiment of a separated high-grade highway with double lanes each direction at Beiluhe in the Qinghai-Tibet Plateau to investigate the thermal characteristics of a novel composite Embankment combined with L-shaped TPCTs, crushed-rock revetments and insulation, as well as an unprotected Embankment (as a control). Experimental results indicate that the composite Embankment can effectively cool the underlying permafrost and raise the permafrost table under the separated high-grade highway with a wide and dark-colored pavement, whereas the unprotected Embankment cannot. This composite Embankment should be considered for application to separated high-grade highways with double lanes each direction in permafrost regions, such as the planned Qinghai-Tibet Expressway.
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evaluating the cooling performance of crushed rock interlayer Embankments with unperforated and perforated ventilation ducts in permafrost regions
Energy, 2015Co-Authors: Mingyi Zhang, Xiyin Zhang, Wansheng Pei, Yuanming LaiAbstract:The crushed-rock interlayer Embankment with ventilation ducts has been advocated to stabilize the permafrost stratum under expressways in permafrost regions. This Embankment must render better cooling effect than railway Embankments because the expressway surface is wider and hotter. To this purpose, the walls of the ventilation ducts need to be perforated. This study evaluates the cooling performance of the rushed-rock interlayer Embankments with unperforated and perforated ventilation ducts along an expressway in permafrost regions of the Qinghai-Tibet Plateau. A three-dimensional numerical model is developed based on heat and mass transfer theories. The model includes the coupled heat transfer between air and ventilation duct wall, the air convective heat transfer in crushed-rock layer, and the heat conduction with phase change in soil layers. The numerical results indicate that if the ventilation ducts are perforated and embedded at the top of the crushed-rock interlayer, the cooling effect of the Embankment can be greatly enhanced. A good cooling performance can still be achieved even if the centerline spacing of the perforated ventilation ducts is enlarged to 4 m to facilitate the construction. The crushed-rock interlayer Embankment with perforated ventilation ducts is a better candidate structure for expressways in permafrost regions of the Qinghai-Tibet Plateau.
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thermal stability analysis of crushed rock Embankments on a slope in permafrost regions
Cold Regions Science and Technology, 2014Co-Authors: Wansheng Pei, Mingyi Zhang, Yuanming Lai, Long Jin, Jon HarborAbstract:Abstract Highways/railways often pass across slope areas and their Embankments are often built on the slopes in permafrost regions. It is difficult to ensure the thermal stability of the Embankments at the slopes due to the effect of slopes. To protect the underlying permafrost, the crushed-rock Embankments are often used in the slope areas. Therefore, it is very necessary to explore the thermal state of crushed-rock Embankments located on the slopes. In this study, we studied numerically the temperature characteristics of three kinds of crushed-rock Embankments located on a slope under global warming, i.e. crushed-rock interlay Embankment, crushed-rock interlayer-revetment Embankment and crushed-rock base Embankment. Numerical results indicate that the crushed-rock interlayer Embankment and the crushed-rock interlayer-revetment Embankment, located on a slope with a ratio of 1:3.73 (about 15° from the horizontal), cannot effectively eliminate the negative effect of climate warming and construction-induced warming, and the effect of slope is still obvious on the thermal stability of permafrost under the crushed-rock interlayer Embankment. However, the crushed-rock base Embankment can significantly reduce the temperature of underlying permafrost and keep the underlying permafrost table stable for a long term; furthermore, the ground temperatures under the long side slope are far lower than those under the short side slope, and this will be more advantageous to control the slide of the Embankment located on a slope and increase its stability. We also find that the three kinds of Embankments cannot all remove the thermal effects of construction from themselves in a short term. Generally speaking, the crushed-rock base Embankment structure can be very advantageous to the thermal stability of the Embankment on a slope.
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nonlinear thermal analysis for qing tibet railway Embankments in cold regions
Journal of Cold Regions Engineering, 2003Co-Authors: Yuanming Lai, Fujun NiuAbstract:Heat convection in ballast mass in railway Embankments is a problem of heat convection in porous media. In order to calculate the temperature distribution of the Qing-Tibet railway Embankment from the governing equations used to study forced convection for incompressible fluids porous media, detailed finite-element formulas for heat convection in porous media are derived using Galerkin’s method. The temperature distributions on central lines of the traditional railway Embankment, the ripped-rock Embankment, and the ripped-rock revetment Embankment that were constructed on July 15, 2002 have been analyzed and compared on July 15, October 15 in the 24th year after construction, and January 15 in the 25th year after construction under the climatic and geological conditions on the Qing-Tibet Railway. The calculated results indicate that the traditional railway Embankment will raise the permafrost temperature under the Embankment base and make the permafrost Embankment thermally unstable. The ripped-rock emban...
Jie Han - One of the best experts on this subject based on the ideXlab platform.
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spring based trapdoor tests investigating soil arching stability in Embankment fill under localized surface loading
Journal of Geotechnical and Geoenvironmental Engineering, 2021Co-Authors: Mahdi Alnaddaf, Jie HanAbstract:AbstractPile-supported (PS) Embankments have been used increasingly to support highways and railways on soft subsoils. In addition to the self-weight of the Embankment, this Embankment system is of...
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displacements of column supported Embankments over soft clay after widening considering soil consolidation and column layout numerical analysis
Soils and Foundations, 2014Co-Authors: Walid El Kamash, Jie Han, F AsceAbstract:The common challenges for constructing Embankments on soft clay include low bearing capacity, large total and differential settlements, and slope instability. Different techniques have been adopted to improve soft clay, such as the use of foundation columns including stone columns, deep mixed columns, and vibro-concrete columns, etc. Due to increased traffic volume, column-supported Embankments may be widened to accommodate the traffic capacity need. Adding a new Embankment to an existing Embankment generates additional stresses and deformations under not only the widened portion but also the existing Embankment. Differential settlements between and within the existing Embankment and the widened portion may cause pavement distresses. Limited research has been conducted so far to investigate widening of column-supported Embankments. In this study, a two-dimensional finite difference numerical method was adopted. This numerical method was first verified against field data and then used for the analysis of widened column-supported Embankments over soft clay. The modified Cam-Clay model was used to model the soil under the existing Embankment and the widened portion. Mechanically and hydraulically coupled numerical models were created to consider the consolidation of the foundation soil under the existing Embankment and the widened portion. Different layouts of foundation columns under the existing Embankment and the widened portion were investigated. The numerical results presented in this paper include the vertical and horizontal displacements, the maximum settlements, the transverse gradient changes, and the stress concentration ratios, which depended on column spacing. The columns installed under the connection side slope were most effective in reducing the total and differential settlements, horizontal displacement, and transverse gradient change of the widened Embankment.
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dem analysis of stresses and deformations of geogrid reinforced Embankments over piles
International Journal of Geomechanics, 2012Co-Authors: Jie Han, Anil Bhandari, Fei WangAbstract:AbstractThe geosynthetic-reinforced pile-supported Embankment is one of the favorable ground improvement techniques used in the construction of earth structures over a compressible soil when limited construction time is available and limited deformation is permissible. Various methods are available for the design of the geosynthetic-reinforced platform based on various load transfer mechanisms from the Embankment to the piles and the compressible soil. The existence of the geosynthetic layer makes the mechanisms more complex. This study focuses on the behavior of geogrid-reinforced Embankments over piles compared with the behavior of unreinforced Embankments. The numerical simulations of the unreinforced and reinforced pile-supported Embankments were conducted using the discrete element method (DEM). The Embankment fill was simulated using unbonded graded aggregates of diameters ranging from 9.2 to 20.8 mm and the geogrid was simulated using bonded particles. This study investigated the changes of vertica...
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coupled mechanical and hydraulic modeling of geosynthetic reinforced column supported Embankments
Journal of Geotechnical and Geoenvironmental Engineering, 2009Co-Authors: Jie Huang, Jie Han, Sadik OztoprakAbstract:Geosynthetic-reinforced column-supported (GRCS) Embankments have increasingly been used in the recent years for accelerated construction. Numerical analyses have been conducted to improve understanding and knowledge of this complicated Embankment system. However, most studies so far have been focused on its short-term or long-term behavior by assuming an undrained or drained condition, which does not consider water flow in saturated soft soil (i.e., consolidation). As a result, very limited attention has been paid to a settlement-time relationship especially postconstruction settlement, which is critical to performance of pavements on Embankments or connection between approach Embankments and bridge abutments. To investigate the time-dependent behavior, coupled two-dimensional mechanical and hydraulic numerical modeling was conducted in this study to analyze a well-instrumented geotextile-reinforced deep mixed column-supported Embankment in Hertsby, Finland. In the mechanical modeling, soils and DM columns were modeled as elastic-plastic materials and a geotextile layer was modeled using cable elements. In the hydraulic modeling, water flow was modeled to simulate generation and dissipation of excess pore water pressures during and after the construction of the Embankment. The numerical results with or without modeling water flow were compared with the field data. In addition, parametric studies were conducted to further examine the effects of geosynthetic stiffness, column modulus, and average staged construction rate on the postconstruction settlement and the tension in the geosynthetic reinforcement.
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numerical analysis of foundation columns to support widening of Embankments
Computers and Geotechnics, 2007Co-Authors: Jie Han, Sadik Oztoprak, Robert L Parsons, Jie HuangAbstract:Abstract Increased traffic volume has made it necessary to increase highway capacities by widening Embankments and pavements. Adding a new Embankment to an existing Embankment induces additional stresses and deformations beneath the widened and existing portions of the Embankment. Differential settlement may develop between and within the new and existing portions of the Embankment, especially over soft soils. This differential settlement often causes pavement distress, such as longitudinal cracks or the drop-off (or sinking) of pavement sections. Different techniques have been adopted to remedy these problems, including the use of foundation columns, such as deep mixed columns, vibro-concrete columns, stone columns, and aggregate piers. However, design procedures for foundation columns constructed for this purpose are not well developed. The analyses of eight cases of column-supported widened Embankments and two untreated foundations are presented in this paper. The factors considered include the consolidation of foundation soils under existing Embankments and the spacing, region, and modulus of foundation columns. Two-dimensional finite difference software was used after the calibration of the model against a field case study and numerical analyses were conducted to investigate stresses and deformations of the widened Embankments over soft soil with or without the remediation of foundation columns. The results presented in this paper include the vertical and the horizontal displacements, the maximum settlements, the transverse gradient change, and the distribution of the additional stresses induced by the widening. Recommendations are made for the design of foundation columns to remedy roadway pavement failure due to widening of Embankments.