Dynamic Response Analysis of Geogrid Reinforced Embankment Supported by CFG Pile Structure During a High-Speed Train Operation

Abstract

The performance of railroad structure has a tremendous influence on the safety and stable operation of high-speed trains. Strong vibrations and the degradation rate of the track are the main factors affecting the transport safety of a railroad built over a weak soil. Geogrid reinforced embankment supported by pile structure is a new efficient construction technique used to ensure the stability and enhance the performance of the railroad system; but only a few studies are oriented to its behavior under train operation. This paper investigates the dynamic response of geogrid reinforced embankment supported by cement fly-ash gravel pile structure during a high-speed train operation. The establishment of a realistic simulation model for railroad subjected to a moving train load, is an important first step towards the reliable design of geogrid reinforced embankment supported by pile structure. Thus, a 3D nonlinear FEM has been established to simulate the instrumented Harbin-Dalian railway test section. Each train carriage was modeled as a transient dynamic load through a user-defined Dload subroutine. The developed model was successfully validated by the dynamic response recorded from the field test section. The improvement of the railroad structure by the CFG piles and geogrids contributed significantly to the reduction of the vibration in the structure, which attenuates 1.2 times faster with the structure depth, even under overload conditions. Moreover, the phenomenon of resonance observed when the train reaches speeds of 100 and 260 km/h were annihilated. The analysis of the stress distribution within the embankment revealed that a dynamic arch is formed in the embankment at 2 m from the ground. The stress onto the pile was 16 times greater than that acted on the soil and the tensile stress developed in the geogrid was high at the piles edge below. In addition, the coupling effect of geogrid with various tensile strengths and the piles with different strength grades indicated that the combination of a high-strength pile and geogrid significantly reduces the displacement gap due to the variation of train speed. As a result, the vibrations of the track were almost constant during the train operation; thus, ensuring comfort to passengers and reducing the risk of derailment.

Mechanical Performance and Void Structure Change of Foamed Cement Paste Subjected to Static and Cyclic Loading under Plane Strain Conditions

“…The cyclic loading adopted a square wave load at a load frequency of 2 Hz considering the typical range of load frequency in transportation [ 37 , 38 , 39 ]. The dynamic load had load levels of 0.2, 0.5 and 0.8, the same as the static loading tests.…”

Impact Assessment of Asphalt Concrete in Geogrid-Reinforced-Pile-Supported Embankment During High-Speed Train Traffic

“…A 3D nonlinear finite element model (FEM) of a GRSP system was established through the Abaqus program to achieve the purpose (Abaqus, 2011). The high-speed train (HST) moving wheel load has been performed as a transitory dynamic load implemented via a user-defined Fortran subroutine (Chango et al, 2019). The viscoelastic behaviour of asphalt concrete material was incorporated into the model for further accurate characterisation of its dynamic properties.…”

“…The ground, reinforced by CFG (cement fly-ash gravel) piles to support the embankment, consists of loess clay 10 m thick, silty clay 10 m thick and silt 12 m thick. All piles, each 20 m in length and 0.5 m in diameter are arranged in an equilateral triangle with a spacing of 1.5 m (Chango et al, 2019).…”

“…All solid section meshes are eight nodes linear brick with hourglass control and reduced integration. The 4-node quadrilateral membrane with hourglass control and reduced integration was used to describe the geogrid mesh (Chango et al, 2019;Zienkiewicz et al, 2005). The division of the FEM into two equal parts of the tested section geometry makes it possible to restrain any X-direction translation to symmetry boundary.…”

“…However, minimizing structure vibration to improve passenger comfort remains a fundamental concern in research. Some studies were conducted to optimize the dynamic of railway system response through the structural design, maintenance and modernization of the railroad system for high-speed trains (Chango et al, 2019;Gailienė & Ramūnas, 2019;Liu & Shao, 2011;Zakeri et al, 2017). Through the experimental test, Sysyn et al (2019) showed that the ballast layer consolidation significantly influences the distribution of stresses under the sleeper.…”