It has been proven that crushed rock layers used in roadbed construction in permafrost regions have a cooling effect. The main reason is the existence of large porosity of the rock layers. However, due to the strong w...It has been proven that crushed rock layers used in roadbed construction in permafrost regions have a cooling effect. The main reason is the existence of large porosity of the rock layers. However, due to the strong winds, cold and high radiation conditions on the Qinghai-Tibet Plateau(QTP), both wind-blown sand and/or weathered rock debris blockage might reduce the porosity of the rock layers, resulting in weakening the cooling effect of the crushed rock layer(CRL) in the crushed rock embankment(CRE) of the Qinghai-Tibet Railway(QTR) in the permafrost regions. Such a process might warm the underlying permafrost, and further lead to potential threat to the QTR's integrity and stability. The different porosities corresponding to the different equivalent rock diameters were measured in the laboratory using water saturation method, and an empirical exponential equation between porosity and equivalent rock diameter was proposed based on the measured experimental data and an important finding is observed in our and other experiments that the larger size crushed rock tends to lead to the larger porosity when arbitrarily packing. Numerical tests were carried out to study impacts of porosity on permafrost degradation and differential thaw depths between the sunny and shady shoulders. The results show that the decrease in porosity due to wind-blown sand or weathered rock debris clogging can worsen the permafrost degradation and lead to the asymmetric thermal regime. In the traditional embankment(without the CRL within it), the largest differential thaw depth can reach up to 3.1 m. The optimized porosity appears in a range from 34% to 42% corresponding to equivalent rock diameter from 10 to 20.5 cm. The CRE with the optimized porosities can make underlying permafrost stable and 0 ℃ isotherms symmetric in the coming 50 years, even under the condition that the climate warming can lead to permafrost degradation under the CRE and the traditional embankment. Some practical implications were proposed to benefit the future design, construction and maintenance of CRE in permafrost regions.展开更多
Aimed at the characteristics of permafrost temperature influencing the safety of Qinghai-Tibet Railway and its on-line testing system, comparing the achievement of permafrost study nationwide with those worldwide, an ...Aimed at the characteristics of permafrost temperature influencing the safety of Qinghai-Tibet Railway and its on-line testing system, comparing the achievement of permafrost study nationwide with those worldwide, an automatic testing system of permafrost temperature, containing a master computer and some slave computers, was designed. By choosing high-precise thermistors as temperature sensor, designing and positioning the depth and interval of testing sections, testing, keeping and sending permafrost temperature data at time over slave computers, and receiving, processing and analyzing the data of collecting permafrost temperature over master computer, the change of the permafrost temperature can be described and analyzed, which can provide information for permafrost railway engineering design. Moreover, by taking permafrost temperature testing in a certain section of Qinghai-Tibet Railway as an instance, the collected data of permafrost temperature were analyzed, and the effect of permafrost behavior was depicted under the railway, as well as, a BP model was set up to predict the permafrost characteristics. This testing system will provide information timely about the change of the permafrost to support the safety operation in Qinghai-Tibet Railway.展开更多
The Embankment with Crushed-Stone Slope Protection(ECSSP) in permafrost regions is an effective measure to cool subgrade and protect permafrost.It can mitigate the engineering hazards of the Qinghai-Tibet railway in t...The Embankment with Crushed-Stone Slope Protection(ECSSP) in permafrost regions is an effective measure to cool subgrade and protect permafrost.It can mitigate the engineering hazards of the Qinghai-Tibet railway in the permafrost regions. Considering the influence of the noctumal cold air during summer months in Qinghai-Tibet Plateau。展开更多
In the realm of high-speed railway bridge engineering,managing the intricacies of the track-bridge system model(TBSM)during seismic events remains a formidable challenge.This study pioneers an innovative approach by p...In the realm of high-speed railway bridge engineering,managing the intricacies of the track-bridge system model(TBSM)during seismic events remains a formidable challenge.This study pioneers an innovative approach by presenting a simplified bridge model(SBM)optimized for both computational efficiency and precise representation,a seminal contribution to the engineering design landscape.Central to this innovation is a novel model-updating methodology that synergistically melds artificial neural networks with an augmented particle swarm optimization.The neural networks adeptly map update parameters to seismic responses,while enhancements to the particle swarm algorithm’s inertial and learning weights lead to superior SBM parameter updates.Verification via a 4-span high-speed railway bridge revealed that the optimized SBM and TBSM exhibit a highly consistent structural natural period and seismic response,with errors controlled within 7%.Additionally,the computational efficiency improved by over 100%.Leveraging the peak displacement and shear force residuals from the seismic TBSM and SBM as optimization objectives,SBM parameters are adeptly revised.Furthermore,the incorporation of elastoplastic springs at the beam ends of the simplified model effectively captures the additional mass,stiffness,and constraint effects exerted by the track system on the bridge structure.展开更多
A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement ...A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement (among) the rail, the sleeper and the beam is taken into account. An example is presented and numerical results are compared. The results show that the additional longitudinal forces calculated with the new model are less than those of the previous, especially in the case of the flexible pier bridges. The new model is also suitable for the analysis of the additional longitudinal force transmission between rails and bridges of ballastless track with small resistance fasteners without taking the sleeper displacement into account, and compared with the ballast bridges, the ballastless bridges have a much stronger additional longitudinal force transmission between the continuously welded rails and the bridges.展开更多
The climate warming,which has an evident effect on the warm/ice-rich permafrost,should be considered in the engineering design of the Qinghai-Tibet Railway in permafrost areas.Based on the rule mentioned above,many de...The climate warming,which has an evident effect on the warm/ice-rich permafrost,should be considered in the engineering design of the Qinghai-Tibet Railway in permafrost areas.Based on the rule mentioned above,many design ideas and measures such as cooling embankment and controling of heat conduction,radiation and convection were proposed during the construction of the Qinghai-Tibet Railway to reduce the permafrost temperature and to reduce the impact of climate warming on the railway.These measures ensure the stability of the railway embankment in permafrost regions.展开更多
基金Project(2012CB026101)supported by the National Key Basic Research Program of China(973 Program)Project(41121061)supported by the Program for Innovative Research Group of Natural Science Foundation of China+2 种基金Project(143GKDA007)supported by the Science and Technology Major Project of the Gansu ProvinceProject(SKLFSE-ZY-16)supported by the State Key Laboratory of Frozen Soil Engineering,ChinaProject supported by the West Light Foundation of CAS for G.Y.Li
文摘It has been proven that crushed rock layers used in roadbed construction in permafrost regions have a cooling effect. The main reason is the existence of large porosity of the rock layers. However, due to the strong winds, cold and high radiation conditions on the Qinghai-Tibet Plateau(QTP), both wind-blown sand and/or weathered rock debris blockage might reduce the porosity of the rock layers, resulting in weakening the cooling effect of the crushed rock layer(CRL) in the crushed rock embankment(CRE) of the Qinghai-Tibet Railway(QTR) in the permafrost regions. Such a process might warm the underlying permafrost, and further lead to potential threat to the QTR's integrity and stability. The different porosities corresponding to the different equivalent rock diameters were measured in the laboratory using water saturation method, and an empirical exponential equation between porosity and equivalent rock diameter was proposed based on the measured experimental data and an important finding is observed in our and other experiments that the larger size crushed rock tends to lead to the larger porosity when arbitrarily packing. Numerical tests were carried out to study impacts of porosity on permafrost degradation and differential thaw depths between the sunny and shady shoulders. The results show that the decrease in porosity due to wind-blown sand or weathered rock debris clogging can worsen the permafrost degradation and lead to the asymmetric thermal regime. In the traditional embankment(without the CRL within it), the largest differential thaw depth can reach up to 3.1 m. The optimized porosity appears in a range from 34% to 42% corresponding to equivalent rock diameter from 10 to 20.5 cm. The CRE with the optimized porosities can make underlying permafrost stable and 0 ℃ isotherms symmetric in the coming 50 years, even under the condition that the climate warming can lead to permafrost degradation under the CRE and the traditional embankment. Some practical implications were proposed to benefit the future design, construction and maintenance of CRE in permafrost regions.
基金Project(2007XM036) supported by the Science and Technology of Beijing Jiaotong University, China
文摘Aimed at the characteristics of permafrost temperature influencing the safety of Qinghai-Tibet Railway and its on-line testing system, comparing the achievement of permafrost study nationwide with those worldwide, an automatic testing system of permafrost temperature, containing a master computer and some slave computers, was designed. By choosing high-precise thermistors as temperature sensor, designing and positioning the depth and interval of testing sections, testing, keeping and sending permafrost temperature data at time over slave computers, and receiving, processing and analyzing the data of collecting permafrost temperature over master computer, the change of the permafrost temperature can be described and analyzed, which can provide information for permafrost railway engineering design. Moreover, by taking permafrost temperature testing in a certain section of Qinghai-Tibet Railway as an instance, the collected data of permafrost temperature were analyzed, and the effect of permafrost behavior was depicted under the railway, as well as, a BP model was set up to predict the permafrost characteristics. This testing system will provide information timely about the change of the permafrost to support the safety operation in Qinghai-Tibet Railway.
文摘The Embankment with Crushed-Stone Slope Protection(ECSSP) in permafrost regions is an effective measure to cool subgrade and protect permafrost.It can mitigate the engineering hazards of the Qinghai-Tibet railway in the permafrost regions. Considering the influence of the noctumal cold air during summer months in Qinghai-Tibet Plateau。
基金Project(2022YFC3004304)supported by the National Key Research and Development Program of ChinaProjects(52078487,U1934207,52178180)supported by the National Natural Science Foundation of China+2 种基金Project(2022TJ-Y10)supported by the Hunan Province Science and Technology Talent Lifting Project,ChinaProject(2023QYJC006)supported by the Frontier Cross Research Project of Central South University,ChinaProject(SKL-IoTSC(UM)-2024-2026/ORP/GA08/2023)supported by the Science and Technology Development Fund and the State Key Laboratory of Internet of Things for Smart City(University of Macao),China。
文摘In the realm of high-speed railway bridge engineering,managing the intricacies of the track-bridge system model(TBSM)during seismic events remains a formidable challenge.This study pioneers an innovative approach by presenting a simplified bridge model(SBM)optimized for both computational efficiency and precise representation,a seminal contribution to the engineering design landscape.Central to this innovation is a novel model-updating methodology that synergistically melds artificial neural networks with an augmented particle swarm optimization.The neural networks adeptly map update parameters to seismic responses,while enhancements to the particle swarm algorithm’s inertial and learning weights lead to superior SBM parameter updates.Verification via a 4-span high-speed railway bridge revealed that the optimized SBM and TBSM exhibit a highly consistent structural natural period and seismic response,with errors controlled within 7%.Additionally,the computational efficiency improved by over 100%.Leveraging the peak displacement and shear force residuals from the seismic TBSM and SBM as optimization objectives,SBM parameters are adeptly revised.Furthermore,the incorporation of elastoplastic springs at the beam ends of the simplified model effectively captures the additional mass,stiffness,and constraint effects exerted by the track system on the bridge structure.
文摘A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement (among) the rail, the sleeper and the beam is taken into account. An example is presented and numerical results are compared. The results show that the additional longitudinal forces calculated with the new model are less than those of the previous, especially in the case of the flexible pier bridges. The new model is also suitable for the analysis of the additional longitudinal force transmission between rails and bridges of ballastless track with small resistance fasteners without taking the sleeper displacement into account, and compared with the ballast bridges, the ballastless bridges have a much stronger additional longitudinal force transmission between the continuously welded rails and the bridges.
基金This research was supported in part by the Outstanding Youth Foundation Project of the Natural Science Foundation of China(Grant No.40625004).The authors are grateful to Jiang Guanli for English editing of this article.
文摘The climate warming,which has an evident effect on the warm/ice-rich permafrost,should be considered in the engineering design of the Qinghai-Tibet Railway in permafrost areas.Based on the rule mentioned above,many design ideas and measures such as cooling embankment and controling of heat conduction,radiation and convection were proposed during the construction of the Qinghai-Tibet Railway to reduce the permafrost temperature and to reduce the impact of climate warming on the railway.These measures ensure the stability of the railway embankment in permafrost regions.
