Numerical Investigation of Stress Concentration Phenomenon in Piled Embankment under Moving Train Loads

2012 ◽  
Vol 193-194 ◽  
pp. 980-983
Author(s):  
Pham Ngoc Thach ◽  
Gang Qiang Kong
Keyword(s):  
Stress Concentration ◽  
High Speed ◽  
Numerical Study ◽  
Soft Soil ◽  
Explicit Finite Element ◽  
Ground System ◽  
Piled Embankment ◽  
Moving Train ◽  
Stiff Soil ◽  
Concentration Phenomenon

A numerical study is performed to investigate the stress concentration phenomenon in a piled embankment during high-speed train passage. In the numerical simulation, the loading of a moving train is first represented in the model as a series of time-varying equivalent concentrated forces vertically acting on the ballast surface, and the explicit finite element method (FEM) is then used to analyze the ballast-embankment-ground system subjected to the equivalent forces. The study shows that owing to the very high stiffness of the piles relative to the soft soil, a majority of the wave energy, which is generated by the passage of wheel axles, is concentrated to the improving piles and transferred down to the stiff soil stratum. By this stress concentration phenomenon, the soft soil surrounding the piles is subjected to less stress, and thus preventing undesirable dynamic effects that could be induced in the soft soil.

Numerical Study on the Stress Concentration Phenomenon in the Membranes of PEMFCs in an Assembled State

2020 ◽  
Vol 146 (5) ◽  
pp. 04020053
Author(s):  
Hui Kang ◽  
Zhi-Gang Zhan ◽  
Xiao-Fan Yang ◽  
Zhi-Bo Zhang ◽  
Jin-Rong Shi ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Numerical Study ◽  
Concentration Phenomenon

scholarly journals Experimental and Numerical Study of the Dynamic Response of XCC Pile–Raft Foundation under High-Speed Train Loads

2021 ◽  
Vol 11 (19) ◽  
pp. 9260
Author(s):  
Qiang Fu ◽  
Jie Yuan
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Large Scale ◽  
Numerical Study ◽  
Soft Soil ◽  
Composite Foundation ◽  
Scale Model ◽  
Vibration Velocity ◽  
Wheel Load ◽  
Foundation Soil

A series of dynamic large-scale model tests and three-dimensional finite element analyses were conducted to investigate the dynamic response of track embankment and XCC pile-raft composite foundation in soft soil for a ballastless high-speed railway under moving train loads. The results indicate that the vibration velocity obtained from the FE numerical simulation agrees well with that from the model test in vibration waveform, amplitude, and frequency characteristics. The peak values corresponding to the passing frequency of train carriage geometry (lc = 25 m), bogie (lab = 7.5 m), and axle distance (lwb = 2.5 m) respectively reflect the characteristic frequencies of the train compartment, adjacent bogie, and wheel load passing through. The peak velocity significantly depends on the distance from the track center in the horizontal direction, of which the attenuation follows the exponential curve distribution. The vibration velocities decrease rapidly within embankment, show a vibration enhancement region from raft to the 1 m depth of foundation soil, then decreases gradually along the subsoil foundation, to a very low level at the bottom of the subsoil, which is much lower than that at the track slab and roadbed. The pile-raft composite foundation can reduce the vibration level effectively and improve the safety of trains running in soft soil areas.

Rail movement and ground waves caused by high-speed trains approaching track-soil critical velocities

2000 ◽  
Vol 214 (2) ◽  
pp. 107-116 ◽  
Author(s):  
V. V. Krylov ◽  
A. R. Dawson ◽  
M. E. Heelis ◽  
A. C. Collop
Keyword(s):  
High Speed ◽  
Soft Soil ◽  
Rayleigh Surface Wave ◽  
Structural Vibrations ◽  
Wave Velocities ◽  
Bending Waves ◽  
Ground System ◽  
High Speed Trains ◽  
Critical Velocities ◽  
Theoretical Results

The increased speeds of modern trains are normally accompanied with increased transient movements of the rail and ground, which are especially high when train speeds approach some critical wave velocities in the track-ground system. These transient movements may cause large rail deflections, as well as structural vibrations and associated noise in nearby buildings. There are two main critical wave velocities in the track-ground system: the velocity of the Rayleigh surface wave in the ground and the minimum phase velocity of bending waves propagating in the track supported by ballast, the latter velocity being referred to as the track critical velocity. Both these velocities can be exceeded by modern high-speed trains, especially in the case of very soft soil where both critical velocities become very low. The discussion in this paper focuses on the effects of transient rail deflections on associated ground vibrations in the cases of train speeds approaching and exceeding Rayleigh wave and track critical velocities. The obtained theoretical results are illustrated by numerical calculations for TGV and Eurostar high-speed trains travelling along typical tracks built on soft soil.

Thermal comfort analysis of a high-speed train cabin considering the solar radiation effects

2019 ◽  
Vol 29 (8) ◽  
pp. 1101-1117
Author(s):  
Lin Yang ◽  
Xiangdong Li ◽  
Jiyuan Tu
Keyword(s):  
Solar Radiation ◽  
Thermal Comfort ◽  
High Speed ◽  
Radiation Effects ◽  
Numerical Study ◽  
Thermal Conditions ◽  
Long Distance ◽  
High Speed Rail ◽  
Hot Weather ◽  
Cabin Environment

Due to the fast development of high-speed rail (HSR) around the world, high-speed trains (HSTs) are becoming a strong competitor against airliners in terms of long-distance travel. Compared with airliner cabins, HST cabins have much larger window sizes. When the big windows provide better lighting and view of the scenery, they also have significant effects on the thermal conditions in the cabins due to the solar radiation through them. This study presents a numerical study on the solar radiation on the thermal comfort in a typical HST cabin. The effect of solar radiation was discussed in terms of airflow pattern, temperature distribution and thermal comfort indices. Parametric studies with seven different daytime hours were carried out. The effect of using the roller curtain was also studied. The overall cabin air temperature, especially near passengers, was found to have significantly increased by solar radiation. Passengers sitting next to windows were recorded to have an obvious thermal comfort variation at different hours of the day. To improve the passengers’ comfort and reduce energy consumption during hot weather, the use of a curtain could effectively reduce the solar radiation effect in the cabin environment.

scholarly journals Ground settlement prediction of embankment treated with prefabricated vertical drains in soft soil

2018 ◽  
Vol 195 ◽  
pp. 03014
Author(s):  
Siswoko Adi Saputro ◽  
Agus Setyo Muntohar ◽  
Hung Jiun Liao
Keyword(s):  
Numerical Study ◽  
Soft Soil ◽  
Soil Permeability ◽  
K Value ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Prefabricated Vertical Drain ◽  
Actual Settlement ◽  
Final Settlement ◽  
Best Fit

Excessive settlement due to consolidation can cause damage to the structure’s rest on soft soil. The settlement takes place in relatively longer. The preloading and prefabricated vertical drain (PVD) is often applied to accelerate the primary settlement. The issue in this research is the estimation of the settlement. The Asaoka method and the finite element method using PLAXIS-2D are used to estimate the final settlement of a PVD treated embankment. For the former, a complete record of the settlement was required; for the latter, some ground parameters are needed for the PLAXIS-2D analysis, such as the permeability of the soil. Because the installation process of PVD tends to influence the permeability of the in-situ soil around the PVD, the soil permeability after the installation of PVD needs to be adjusted. The numerical results were compared with actual settlement data to find out the best-fit input parameters (i.e. soil permeability) of the actual data. It was found that the best-fit soil permeability (k) used in the numerical study was about one-half of the k value determined from the laboratory test. The Root Mean Square Deviation shows that the settlement predicted by the numerical analysis has approximately 30% of the actual settlement.

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