The Effect of CFG-Pile Caps and Cushion to Stability of Embankment

2011 ◽  
Vol 287-290 ◽  
pp. 797-800
Author(s):  
Zhen Hua Wu ◽  
Jian Yi Yuan
Keyword(s):  
High Speed ◽  
Stress Ratio ◽  
Dynamic Stress ◽  
Vertical Section ◽  
Composite Foundation ◽  
High Speed Railway ◽  
Dynamic Displacement ◽  
Wide Range ◽  
Pile Caps ◽  
Cfg Pile

Subgrade diseases are exposed more and more serious with raising speed of existing railway in wide range. Dynamic numerical simulation had been done to analyze the effect of CFG-pile caps and cushion in composite foundation with CFG-pile in low embankment of Beijing-Shanghai high-speed railway. Distribution rules of dynamic displacement and dynamic stress of the subgrade surface and ground surface on the cross section, attenuation rules of dynamic response and dynamic stress ratio between pile and soil on the vertical section were studied. It shows that the dynamic stress of pile and soil generally attenuates in depth and attenuation of dynamic stress ratio between pile and soil mostly concentrates in the scope of 10m beneath the ground and dynamic stress caused by train load is undertaken by the pile. Moreover the scheme of CFG-pile with no pile caps and rigid cushion scheme is superior to that of pile caps and flexible cushion scheme for enhancing dynamic stability and reducing dynamic displacement and stress in low embankment. It will be instructive to control design and construction for the low embankment in Beijing-Shanghai high-speed railway.

Dynamic Response Analysis on Efficacy of CFG-Pile in Different Height Embankment

2011 ◽  
Vol 311-313 ◽  
pp. 145-148
Author(s):  
Jian Xiang
Keyword(s):  
Dynamic Response ◽  
Dynamic Stability ◽  
High Speed ◽  
Stress Ratio ◽  
Dynamic Stress ◽  
Ground Surface ◽  
High Speed Railway ◽  
Dynamic Displacement ◽  
Embankment Height ◽  
Cfg Pile

In order to analyze the effect of embankment height to dynamic stability, Cross-section in the Beijing-Shanghai high-speed railway is chosen and the numerical simulation calculation method is applying. Distributing rules of dynamic displacement and dynamic stress of the subgrade surface and ground surface, attenuation rules of dynamic response and dynamic stress ratio between pile and soil on the vertical section were studied. It shows that the dynamic stress of pile and soil generally attenuates in depth and attenuation of dynamic stress ratio between pile and soil mostly concentrates into the scope of 10 meters beneath the ground. Moreover, with the increment of embankment height and attenuation of dynamic stress in direct proportion to the depth, the dynamic stress transferring to ground surface decrease and the dynamic displacement of ground surface minish. As a result, the scheme of CFG-pile with 3m scheme is superior to that of 2m scheme for enhancing dynamic stability and reducing dynamic displacement and stress in low embankment. It will be instructive to control design and construction for the low embankment in Beijing-Shanghai high-speed railway.

Research on Stress Distribution of CFG Pile-Net Composite Foundation in High-Speed Railway

2013 ◽  
Vol 361-363 ◽  
pp. 1833-1837 ◽  
Author(s):  
Jun Cheng ◽  
Ji Wen Zhang
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Stress Ratio ◽  
Field Tests ◽  
Composite Foundation ◽  
Additional Stress ◽  
High Speed Railway ◽  
Soil Stress ◽  
Gravel Pile ◽  
Cfg Pile

Combined with the field tests of CFG (Cement Fly-ash Gravel) pile-net (geogrid) composite foundation in Danyang Test Section of the Beijing-Shanghai High-speed Railway, the settlement, pile-soil stress ratio and additional stress of composite foundation were analyzed by numerical simulation. It shows that the pile-soil stress ratio of CFG pile-net composite foundation is in the range of 4 to 6. And the reasonable distribution of additional stress in composite foundation is also discussed. The results can provide references for the design of the CFG pile-net composite foundation under embankment in high-speed railway.

Studies on the Residual Settlement of CFG Pile Composite Foundation of the Wuhan-Guangzhou High Speed Railway

2012 ◽  
Vol 178-181 ◽  
pp. 1590-1595
Author(s):  
Feng Zhang ◽  
Zhao Yi Xu ◽  
Zhi Yi Li
Keyword(s):  
High Speed ◽  
Soil Layer ◽  
Composite Foundation ◽  
High Speed Railway ◽  
Actual Observation ◽  
Permanent Load ◽  
Cfg Pile Composite Foundation ◽  
Gravel Pile ◽  
Pile Length ◽  
Cfg Pile

Wuhan-Guangzhou passenger special line is the most important backbone of China high speed railway net. The line span is 968 km, among of them; roadbed is 388 km, occupied 40.1% of the total line. Due to the rigorous residual settlement of the roadbed, the CFG (Cement Flayash Gravel) pile is used as the composite foundation to enforce the intensity of roadbed and reduce the post-settlement. The paper studies on CFG pile composite foundation at the Wuhan experimental section, using the finite element numerical simulate the interaction of the pile and pile surrounding soil under the permanent load conditions. The results show that the stimulation model has the more accordance with the actual observation results. The residual settlement comes from the soil layer is bigger than the pile length.

Composite Foundation on Bearing Characteristics and Simulation Analysis CFG Pile for the High Speed Railway

2011 ◽  
Vol 71-78 ◽  
pp. 3827-3831
Author(s):  
A Lan Jiang ◽  
Mei Xia Wang
Keyword(s):  
High Speed ◽  
Simulation Analysis ◽  
Coupling Effect ◽  
Rapid Development ◽  
Composite Foundation ◽  
Treatment Technology ◽  
High Speed Railway ◽  
Cfg Pile Composite Foundation ◽  
Sand And Gravel ◽  
Cfg Pile

With the rapid development of high-speed railway in soft foundation, foundation treatment technology has become mature, the most outstanding is CFG pile composite foundation technique. CFG pile composite foundation is made of cement fly ash gravel pile(CFG pile), pile of soil and sandstone , between sand and gravel several problems such as the medium material composition together constitute layer. It has high bearing of capacity, convenient, low costing, strong adaptability and quality control easier.So it is widely applied and promoted. Under static and dynamic loads, the relations of the high-speed railway CFG pile composite foundation is very complex. In order to further understand the intensity of pile-net structure subgrade stability and deformation, pile , requirements of the high-speed railway roadbed ,it needs to do pile-net structure parameter sensitivity analysis. According to high-speed railway CFG pile composite foundation , the numerical analysis can well solve the coupling effect of piles and soil. So, this paper adopts FLAC3D finite difference software is simulated and analyzed.

Numerical Simulation on the Reinforcing Effect of New CFG Pile-Board Structure Composite Foundation

2011 ◽  
Vol 243-249 ◽  
pp. 2415-2418
Author(s):  
Ding Bang Zhang
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Composite Foundation ◽  
Board Structure ◽  
Treatment Technique ◽  
High Speed Railway ◽  
Concrete Pile ◽  
Soil Stress ◽  
Deformation Compatibility ◽  
Cfg Pile

The new CFG pile-board structure composite foundation is a ground treatment technique based on CFG pile foundation and pile-board structure composite foundation. It can make full use of the load distributing function of board, the bearing capacity and the deformation compatibility of soil between piles, by taking advantage of the pile-platform-soil interaction. A part of soft ground in a high-speed railway was taken as the engineering background and study object. The settlement controlling effect of common CFG pile ground and new CFG pile-board structure composite foundation were analyzed by finite element numerical method, and various factors to the effect on settlement-controlling were discussed. Pile-soil stress ratio of CFG pile and reinforced concrete pile were studied. Some useful conclusions of the numerical simulation of the new CFG pile-board structure composite foundation were obtained.

scholarly journals Model Test Study on the Influence of Train Speed on the Dynamic Response of an X-Section Pile-Net Composite Foundation

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Shanshan Xue ◽  
Yumin Chen ◽  
Hanlong Liu
Keyword(s):  
High Speed ◽  
Dynamic Stress ◽  
Composite Foundation ◽  
Vibration Velocity ◽  
Distribution Characteristics ◽  
Vibration Acceleration ◽  
Foundation Soil ◽  
Dynamic Displacement ◽  
Train Speed ◽  
Train Loading

Based on a large-scale X-section pile-net composite foundation model, we experimentally studied the dynamic characteristics of the pile-net composite foundation under a high-speed railway train load; analyzed the distribution characteristics of the dynamic stress, dynamic displacement, speed, and acceleration of the foundation soil under different train speeds; and investigated the vibration response of the track subgrade foundation system, as well as the distribution characteristics and attenuation pattern of the dynamic stress inside the subgrade foundation under cyclic train loading. The following results are obtained. The peak vertical vibration speed and the peak acceleration attenuate by 90% and 62.5%, respectively, after passing through the embankment. The vibration velocity increases linearly with the train speed; the ratio of the peak dynamic soil stresses at the top of the piles and between the piles is approximately 3.4. The change in train speed does not have a large influence on the peak dynamic displacement or peak dynamic soil stress. The peak spectral vibration acceleration caused by the train loading is located within the range of medium-to-low-frequency vibrations, and the characteristic frequency corresponds to the passing frequency of the bogies and carriages; as the train speed increases, the peak spectral vibration acceleration increases, and the high-frequency components increase significantly.

The Dynamic Analysis of Soft Soil Subgrade in High-Speed Railway Strengthened by PHC Pile

2014 ◽  
Vol 1030-1032 ◽  
pp. 908-911 ◽  
Author(s):  
Zhen Hua Pan ◽  
Kong Ming Yan ◽  
Jin Biao Wu ◽  
Zhe Wang ◽  
Wei Ming Liao
Keyword(s):  
Prestressed Concrete ◽  
High Speed ◽  
Dynamic Stress ◽  
Soft Soil ◽  
Time History ◽  
Composite Foundation ◽  
High Speed Train ◽  
High Speed Railway ◽  
Soft Soil Area ◽  
Soil Area

The combination of PHC pile (prestressed concrete pile) with geogrid to reinforce the foundation has been widely used in high-speed railway, and the response of dynamic stress under the high-speed train is worth studying. By using Midas/GTS NX software to establish a 3-D model of pile-net composite foundation in one section of Hangzhou - Shenzhen line, the influence of pile-net composite foundation generated by high-speed train is studied. Moreover, this paper also studies the distribution and propagation of dynamic stress generated by train load in soft soil area. The results show that the dynamic stress reducing quickly in the embankment structure and the time –history curve of the dynamic stress behaves differently along the depth. With the depth increasing, there is phenomenon of peak superposition in the time-history curve of the vertical dynamic stress. In the meanwhile, the PHC pile is the main structure to propagate and sustain the dynamic stress in soft soil area, and with the tendency of ‘large in the middle, small on both ends’.

An Analysis on Failure Pattern of CFG Pile-Net Composite Foundation of High-Speed Railway

2012 ◽  
Vol 594-597 ◽  
pp. 1357-1362
Author(s):  
Dan Ping Jiang ◽  
Bing Long Wang
Keyword(s):  
High Speed ◽  
Shear Failure ◽  
Soft Soil ◽  
Composite Foundation ◽  
Failure Pattern ◽  
Lagrangian Analysis ◽  
High Speed Railway ◽  
Foundation Treatment ◽  
Sliding Soil ◽  
Cfg Pile

CFG pile-net composite foundation has the advantages of small post construction settlement and uneven settlement, easy control of construction quality and fast construction speed. It`s widely used in subgrade engineering of high-speed railway. However, in coastal soft soil area, phenomena like breaking pile, collapsed embankment, cracking in embankment surface, undue settlement or convergence appeared in many places where railway CFG pile was improved during the foundation treatment, filling and preloading. Four numerical calculations were performed to investigate the failure pattern of CFG pile-net composite foundation with FLAC3D ( Fast Lagrangian Analysis of Continua, 3 dimensions) software. The paper describes four failure pattern, they are slip circle shear failure, pile tilt failure, roadbed sliding, soil sliding at pile end respectively through the analysis of the embankment and pile displacement as well as embankment deformation.

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