Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simul...Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simulation(DES) with standard SpalartAllmaras(SA) model. The Reynolds number is 4.0×105 in this calculation. The region is three-dimensional. Since the wind barrier and trains are almost invariable cross-sections, only 25 m along the track is modeled. The height of embankment ranges from 1 m to 5 m and the wind barrier is 3 m high. The results show that the wind speed changes obviously before the wind barrier on the horizontal plane, which is 4.5 m high above the track. The speed of wind reduces gradually while approaching the wind barrier. It reaches the minimum value at a distance about 5 m before the wind barrier, and increases dramatically afterwards. The speed of wind at this location is linear with the speed of far field. The train aerodynamic coefficients decrease sharply with the increment of the embankment height. And they take up the monotonicity. Meanwhile, when the height increases from 3 m to 5 m, they just change slightly. It is concluded that the optimum anemometer location is nearly 5 m in front of the wind barrier.展开更多
Tsunamis have a severe impact on marine coastal structures.Tsunami is generally simplified as solitary wave as they propagate,and the presence of the aftermath of Tsunami is similar to a second solitary wave.Waveform ...Tsunamis have a severe impact on marine coastal structures.Tsunami is generally simplified as solitary wave as they propagate,and the presence of the aftermath of Tsunami is similar to a second solitary wave.Waveform evolution occurs as solitary wave propagate down a gentle slope.This paper reveals the propagation of double solitary waves and slope climbing by numerical simulation where the prototype of the embankment is around Shantou city in the Guangdong Province,China.It not only enriches the theory of solitary wave,but also has important implications for the analysis of tsunami disaster mechanism and the hydrodynamic load characteristics of structures.Based on the average Navier-Stokes equation and the VOF approach,numerical simulation results are given,including changes in the velocity field of the climbing and falling process species.The results show that the double solitary waves produce a strong reflux effect,which results in the second solitary wave climbing significantly less than the height of the first solitary wave without the influence of the current.At the same time,double solitary waves can have a much stronger effect on the embankment.展开更多
This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment ...This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment section of Qinghai-Tibet highway,computational region for numerical analysis was defined.And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data.The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling.Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing.And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment.Raising embankment height can improve the thermal stability; however,the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing.Thus,to construct expressway with wide embankment in permafrost regions of Qinghai-Tibet Plateau,effective measures need to be considered to improve the thermal stability of underlying permafrost.展开更多
The construction of CKE road embankments is undertaken over soft soils, which include peats, organic soils, clays and sludge. The moisture content of peat is up to 700% and void ratio is up to 11.99. It＇s very easy f...The construction of CKE road embankments is undertaken over soft soils, which include peats, organic soils, clays and sludge. The moisture content of peat is up to 700% and void ratio is up to 11.99. It＇s very easy for the embankments of high moisture content, high void ratio and of the high compression nature to cause too much settlement and loss of stability. Embankment stability during construction and residual settlement of pavement during service period are two major challenges to be faced of the design and construction. This paper outlines the site investigation, laboratory tests and monitoring data in a few selected existing preloading areas, and presents the back-analysis results of the modified secondary compression indices of in-situ soft materials. It is found that the early monitoring data after primary settlement completion are a more reliable approach to estimate the residual settlements within a nominated duration.展开更多
基金Projects(51075401,U1334205)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0833)supported by the New Century Excellent Talents in University,China+2 种基金Project supported by the Scholarship Award for Excellent Innovative Doctoral Student granted by Central South University,ChinaProject(2012T002-E)supported by the Science and Technology Research and Development Program of Ministry of Railway,ChinaProject(14JJ1003)supported by the Natural Science Foundation of Hunan Province,China
文摘Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simulation(DES) with standard SpalartAllmaras(SA) model. The Reynolds number is 4.0×105 in this calculation. The region is three-dimensional. Since the wind barrier and trains are almost invariable cross-sections, only 25 m along the track is modeled. The height of embankment ranges from 1 m to 5 m and the wind barrier is 3 m high. The results show that the wind speed changes obviously before the wind barrier on the horizontal plane, which is 4.5 m high above the track. The speed of wind reduces gradually while approaching the wind barrier. It reaches the minimum value at a distance about 5 m before the wind barrier, and increases dramatically afterwards. The speed of wind at this location is linear with the speed of far field. The train aerodynamic coefficients decrease sharply with the increment of the embankment height. And they take up the monotonicity. Meanwhile, when the height increases from 3 m to 5 m, they just change slightly. It is concluded that the optimum anemometer location is nearly 5 m in front of the wind barrier.
基金supported by Comprehensive Geological Survey of Chaoshan Coastal Zone (No. DD20208013)
文摘Tsunamis have a severe impact on marine coastal structures.Tsunami is generally simplified as solitary wave as they propagate,and the presence of the aftermath of Tsunami is similar to a second solitary wave.Waveform evolution occurs as solitary wave propagate down a gentle slope.This paper reveals the propagation of double solitary waves and slope climbing by numerical simulation where the prototype of the embankment is around Shantou city in the Guangdong Province,China.It not only enriches the theory of solitary wave,but also has important implications for the analysis of tsunami disaster mechanism and the hydrodynamic load characteristics of structures.Based on the average Navier-Stokes equation and the VOF approach,numerical simulation results are given,including changes in the velocity field of the climbing and falling process species.The results show that the double solitary waves produce a strong reflux effect,which results in the second solitary wave climbing significantly less than the height of the first solitary wave without the influence of the current.At the same time,double solitary waves can have a much stronger effect on the embankment.
基金Project(2014BAG05B04)supported by the National Science and Technology Support Program,ChinaProject(51378006)supported by the National Natural Science Foundation of ChinaProject(2242015R30027)supported by the Excellent Young Teacher Program of Southeast University,China
文摘This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method(FEM).According to specific embankment section of Qinghai-Tibet highway,computational region for numerical analysis was defined.And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data.The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling.Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing.And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment.Raising embankment height can improve the thermal stability; however,the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing.Thus,to construct expressway with wide embankment in permafrost regions of Qinghai-Tibet Plateau,effective measures need to be considered to improve the thermal stability of underlying permafrost.
文摘The construction of CKE road embankments is undertaken over soft soils, which include peats, organic soils, clays and sludge. The moisture content of peat is up to 700% and void ratio is up to 11.99. It＇s very easy for the embankments of high moisture content, high void ratio and of the high compression nature to cause too much settlement and loss of stability. Embankment stability during construction and residual settlement of pavement during service period are two major challenges to be faced of the design and construction. This paper outlines the site investigation, laboratory tests and monitoring data in a few selected existing preloading areas, and presents the back-analysis results of the modified secondary compression indices of in-situ soft materials. It is found that the early monitoring data after primary settlement completion are a more reliable approach to estimate the residual settlements within a nominated duration.
