Stress distribution in roadbeds of slab tracks with longitudinal discontinuities

Abstract

Stress concentration occurs in the foundations of railway tracks where discontinuous components are located. The exacerbated stress under the expansion joints in slab tracks may trigger foundation failures such as mud pumping. Although the higher stress due to the discontinuities of track structures has been discussed in past studies, few focused on the stress response of roadbeds in slab tracks and quantitatively characterized the stress pattern. In this paper, we performed a dynamic finite element analysis of a track-formation system, incorporating expansion joints as primary longitudinal discontinuities. The configurations of CRTS III slab tracks and the contact conditions between concrete layers were considered. Numerical results show that longitudinal influencing length of induced stress on roadbed under wheel load relates to the contact conditions between concrete layers, increasing nonlinearly at a larger coefficient of friction. Given a measured coefficient of friction of 0.7, the calculated longitudinal influencing length (9.0 m) matches with field data. The longitudinal influencing length is not affected with the increasing velocity. As stress concentration arises with expansion joints, the worst-case scenario emerges when double-axle loads are exerted immediately above the expansion joints between concrete bases. A stress concentration factor C _v on the roadbed is proposed; it increases with the increasing velocity, changing from 1.33 to 1.52 at velocities between 5 and 400 km/h. The stress distribution on roadbeds transforms from a trapezoid pattern at continuous sections to a triangle pattern at points with longitudinal discontinuities. An explicit expression is finally proposed for the stress pattern on roadbed under expansion joints. Although structural discontinuities induce stress raiser, the extent of concentration is mitigated with increasing depth at different velocity levels.

Keywords

Ballastless track / Expansion joint / Dynamic stress / Roadbed / Stress distribution

References

[1] Zhou S Wang B Shan Y. Review of research on high-speed railway subgrade settlement in soft soil area. Railw Eng Sci, 2020 28 2 129-145

[2] Ren J Deng S Zhang K . Design theories and maintenance technologies of slab tracks for high-speed railways in China: a review. Transp Saf Environ, 2021 3 4 1-19

[3] Nguyen VD Luo Q Wang T . Monitoring of an instrumented geosynthetic-reinforced piled embankment with a triangular pile configuration. Int J Rail Transp, 2022

[4] Bian X Li W Hu J . Geodynamics of high-speed railway. Transp Geotech, 2018 17 1 69-76

[5] The national railway administration of China (2014). Code for design of high-speed railway TB10621–2014 (in Chinese)

[6] Luo Q Wei M Lu Q Wang T. Simplified analytical solution for stress concentration ratio of piled embankments incorporating pile–soil interaction. Railw Eng Sci, 2021 29 2 199-210

[7] Zhang W Luo Q Wang T . System reliability evaluation of long railway subgrade slopes considering discrete instability. Railw Eng Sci, 2022

[8] Bian X Wan Z Zhao C . Mud pumping in the roadbed of ballastless high-speed railway. Géotechnique, 2022

[9] Wang T Luo Q Liu M . Physical modeling of train-induced mud pumping in substructure beneath ballastless slab track. Transp Geotech, 2020 23

[10] Li Y Leng W Nie R . Laboratory full-scale model test of subgrade mud pumping for ballastless track of high-speed railway. Int J Rail Transp, 2022 10 2 230-256

[11] Nguyen T Indraratna B Kelly R . Mud pumping under railtracks: mechanisms, assessments and solutions. Aust Geomech J, 2019 54 4 59-80

[12] Nguyen TT Indraratna B. Rail track degradation under mud pumping evaluated through site and laboratory investigations. Int J Rail Transp, 2022 10 1 44-71

[13] Jiang H Bian X Cheng C . Simulating train moving loads in physical model testing of railway infrastructure and its numerical calibration. Acta Geotech, 2016 11 2 231-242

[14] Jiang HG (2014) Dynamic interaction of slab track structure-subgrade system and accumulative settlement in high-speed railways. Zhejiang University (in Chinese)

[15] Wang T Luo Q Liu J . Method for slab track substructure design at a speed of 400 km/h. Transp Geotech, 2020 24

[16] Liu G Luo Q Zhang L . Analysis on the dynamic stress characteristics of the ballastless track subgrade under train loading. J China Railw Soc, 2013 35 9 86-93

[17] Ye Y Cai D Wei S . Distribution characteristics and analytical method of dynamic stress on subgrade of ballastless track for high-speed railway. China Railw Sci, 2020 41 6 1-9

[18] Xue F Zhang J. Spatial Distribution of dynamic stresses in embankment of high-speed railway under moving loads. J China Railw Soc, 2016 38 1 86-91

[19] The national railway administration of China (2017) Code for design of railway track TB 10082–2017 (in Chinese)

[20] Luo Q Zhang R Xie H Tian D. Structural analysis and key parameter of ballastless track subgrade for 400 km/h high-speed railway. China Railw Sci, 2020 41 2 34-44

[21] Zhang R (2017) Exploration of design technique on substructure for 400km/h high-speed railway and 40 t axle-load heavy haul railway. Southwest Jiaotong University (in Chinese)

[22] Zeng Z Wang J Shen S . Experimental study on evolution of mechanical properties of CRTS III ballastless slab track under fatigue load. Constr Build Mater, 2019 210 639-649

[23] Cai X Zhang Q Zhang Y . Deformation law and control limit of CRTSIII slab track under subgrade frost heave. Appl Sci, 2021 11 8 3520

[24] Gu Y Liu J-B Du Y-X. 3D consistent viscous-spring artificial boundary and viscous-spring boundary element. Eng Mech, 2007 24 12 31-37

[25] Liu J Gu Y Du Y. Consistent viscous-spring artificial boundaries and viscous-spring boundary elements. Chin J Geotech Eng, 2006 28 9 1070-1075

[26] Galavi V, Brinkgreve R (2014) Finite element modelling of geotechnical structures subjected to moving loads. In: Numerical methods in geotechnical engineering (NUMGE), Delft, pp235–240

[27] Alimirzaei S Mohammadimehr M Tounsi A. Nonlinear analysis of viscoelastic micro-composite beam with geometrical imperfection using FEM: MSGT electro-magneto-elastic bending, buckling and vibration solutions. Struct Eng Mech, 2019 71 5 485-502

[28] Guo Y Gao J Sun Y Zhai W. Mapping relationship between subgrade settlement and rail deflection of the double-block ballastless track. J China Railw Soc, 2016 38 9 92-100

[29] Gao L Zhao L Qu C Cai X. Analysis on design scheme of CRTSIII slab track structure on roadbed. J Tongji Univ Sci, 2013 41 6 848-855

[30] Liu S Chen X Ma Y . Modelling and in-situ measurement of dynamic behavior of asphalt supporting layer in slab track system. Constr Build Mater, 2019 228

Funding

National Natural Science Foundation of China(41901073)

Sichuan Science and Technology Program (2021YJ0001)