Transverse Cracking of Concrete Base Plate in CRTS III Ballastless Track Structure: Effects of Environmental Boundary Conditions

The cast-in-place concrete base plate is a main member of the China Railway Track System (CRTS) III ballastless track structure that is prone to generating early transverse cracking. Such cracks can dramatically affect the performance and service life of the railway track structure. This study investigated the influence of temperature and moisture boundary conditions on early cracking behavior of the CRTS III base plate by using approaches of both in situ measurements and numerical modelling. In-site measurements of strain and temperature were made in four test series of CRTS III base plates under the same natural environmental condition but cured with different regimes, and a total of 96 measuring positions were monitored for up to 150 days. The results showed that the strain magnitude and distribution in the field base plate, the initial time at cracking, and the observed cracking pattern varied significantly between the different test series. In order to understand the mechanisms that create these transverse cracks and to provide guidelines for the current curing strategy during construction, the characteristics of temperature-induced and moisture-induced stresses were analyzed by using 3D numerical modelling and by considering early-age concrete creep properties, meteorological factors, and the influence from environmental boundary conditions. The calculated results revealed that early-age transverse cracking in CRTS III base plate depends more on drying shrinkage stress than temperature stress. By conducting this study, we expect to provide guidance for reducing or eliminating early cracks of CRTS III concrete base plate.

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Deformation Law and Control Limit of CRTSIII Slab Track under Subgrade Frost Heave

Applied Sciences ◽

10.3390/app11083520 ◽

2021 ◽

Vol 11 (8) ◽

pp. 3520

Author(s):

Xiaopei Cai ◽

Qian Zhang ◽

Yanrong Zhang ◽

Qihao Wang ◽

Bicheng Luo ◽

...

Keyword(s):

High Speed ◽

Base Plate ◽

Element Model ◽

Middle Part ◽

Railway Track ◽

Frost Heave ◽

Track Structure ◽

Slab Track ◽

Plastic Damage ◽

Track Irregularity

In order to find out the influence of subgrade frost heave on the deformation of track structure and track irregularity of high-speed railways, a nonlinear damage finite element model for China Railway Track System III (CRTSIII) slab track subgrade was established based on the constitutive theory of concrete plastic damage. The analysis of track structure deformation under different subgrade frost heave conditions was focused on, and amplitude the limit of subgrade frost heave was put forward according to the characteristics of interlayer seams. This work is expected to provide guidance for design and construction. Subgrade frost heave was found to cause cosine-type irregularities of rails and the interlayer seams in the track structure, and the displacement in lower foundation mapping to rail surfaces increased. When frost heave occured in the middle part of the track slab, it caused the greatest amount of track irregularity, resulting in a longer and higher seam. Along with the increase in frost heave amplitude, the length of the seam increased linearly whilst its height increased nonlinearly. When the frost heave amplitude reached 35 mm, cracks appeared along the transverse direction of the upper concrete surface on the base plate due to plastic damage; consequently, the base plate started to bend, which reduced interlayer seams. Based on the critical value of track structures’ interlayer seams under different frost heave conditions, four control limits of subgrade frost heave at different levels of frost heave amplitude/wavelength were obtained.

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NUMERICAL MODELLING OF THERMAL REGIME OF RAILWAY TRACK - STRUCTURE WITH THERMAL INSULATION (STYRODUR)

Journal of Civil Engineering and Management ◽

10.3846/jcem.2021.14903 ◽

2021 ◽

Vol 27 (7) ◽

pp. 525-538

Author(s):

Libor Ižvolt ◽

Peter Dobeš ◽

Michaela Holešová ◽

Deividas Navikas

Keyword(s):

Numerical Modelling ◽

Thermal Insulation ◽

Thermal Regime ◽

Climatic Factors ◽

Railway Track ◽

Track Structure ◽

Insulation Layer ◽

Surface Level ◽

Main Factors ◽

Climatic Characteristics

This paper presents the results of numerical modelling of the influence of various factors (geometrical layout of the structural layers of the railway track, climatic factors and ballast fouling) on the freezing of railway track structure with a built-in thermal insulation layer of extruded polystyrene (Styrodur). At the same time, the suitability and expediency of incorporating the thermal insulation layer at the sub-ballast upper surface level (i.e. below the rail ballast construction layer), or at the level of subgrade surface are discussed. Numerical modelling results in the main factors that should be taken into account in the dimensioning of the sub-ballast layers with a built-in thermal insulation layer. Based on the data on the depth of freezing of the railway track structure obtained from numerical modelling, a design nomogram for dimensioning was created and subsequently the influence of the changes of climatic characteristics on the freezing of the railway track structure was then mathematically expressed.

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Push Plate Test of CRTS II Slab Ballastless Track: Theoretical Analysis, Experiments, and Numerical Simulation

Shock and Vibration ◽

10.1155/2021/1945385 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Yu Liu ◽

Qianqi Xu ◽

Xiaodan Sun ◽

Guotao Yang ◽

Guotang Zhao

Keyword(s):

Cohesive Zone Model ◽

Theoretical Explanation ◽

Railway Track ◽

Zone Model ◽

Track Structure ◽

Distribution Method ◽

Plate Test ◽

Ballastless Track ◽

Force Displacement ◽

Proportional Distribution

Push plate test is a powerful tool to evaluate the interfacial bond performance of China railway track structure type-II slab ballastless track structure (CRTS II SBTS). However, there is still a lack of theoretical explanation of the push plate test. In this paper, a linear proportional distribution method is proposed in terms of a series of analytical formulas to describe the interfacial force-displacement variation of CRTS II SBTS in different damage stages of the horizontal push plate test. The force-displacement relationship established by the linear proportional distribution method agrees well with that observed in full-scale test. The horizontal push plate test is then simulated, in which a bilinear cohesive zone model (CZM) was adopted to simulate the interface within track structure. The parameters of the CZM are calculated based on the force-displacement curves obtained from scale push plate test. Particularly, the normal cohesive parameters are determined based on the scale vertical push plate test instead of the traditional splitting tensile test. The simulation proves that both the maximum affected length in the undamage stage and the maximum damaged length in the damage stage depend rather on the interfacial stiffness and the material parameters of SBTS than the horizontal load. These two lengths given by the simulation are close to those defined by the proposed linear proportional distribution method. This indicates the reliability of the proposed method and the capability of scale push plate test in determining cohesive parameters.

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Investigation on Interface Damage between Cement Concrete Base Plate and Asphalt Concrete Waterproofing Layer under Temperature Load in Ballastless Track

Applied Sciences ◽

10.3390/app10082654 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2654

Author(s):

Xianhua Chen ◽

Yu Zhu ◽

Degou Cai ◽

Gang Xu ◽

Tao Dong

Keyword(s):

Dynamic Response ◽

Crack Propagation ◽

Asphalt Concrete ◽

Base Plate ◽

Cement Concrete ◽

Damage Initiation ◽

Interface Damage ◽

Ballastless Track ◽

Concrete Base ◽

Temperature Load

The interfacial bond between cement concrete base plate (CCBP) and asphalt concrete waterproofing layer (ACWL) is a weak portion in the newly developed Chinese high-speed railway ballastless track. The interface damage caused due to fluctuating temperature load and dynamic train load is one of the most critical problems in Northern China. This paper aims to investigate the interface damage evolution process under temperature load via experimental and simulation analysis. Full-scale transverse shear tests were performed to explore the interface bond-slip mode of the adjacent ACWL and CCBP. Then, a finite element model of a ballastless track structure was built and a cohesive zone model (CZM) was utilized to model the interface damage initiation, crack propagation, and delamination process under uniform/gradient temperature load. Furthermore, the dynamic response of the ballastless track where CCBP and ACWL were partly/totally debonded was investigated and compared with the perfectly bonded structure. The results demonstrate that bilinear CZM is capable of revealing the interface damage initiation, crack propagation, and delamination process under temperature load. The interface state between the adjacent CCBP and ACWL was greatly affected by temperature changes and the interface bonding state had a great impact on the dynamic response of ballastless track.

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Mechanical Performance of a Ballastless Track System for the Railway Bridges of High-Speed Lines: Experimental and Numerical Study under Thermal Loading

Materials ◽

10.3390/ma14112876 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2876

Author(s):

Yingying Zhang ◽

Lingyu Zhou ◽

Akim D. Mahunon ◽

Guangchao Zhang ◽

Xiusheng Peng ◽

...

Keyword(s):

High Speed ◽

Thermal Loading ◽

Mechanical Performance ◽

Track Structure ◽

Box Girder ◽

High Speed Railway ◽

Ballastless Track ◽

Track System ◽

Girder Bridge ◽

Track Slab

The mechanical performance of China Railway Track System type II (CRTS II) ballastless track suitable for High-Speed Railway (HSR) bridges is investigated in this project by testing a one-quarter-scaled three-span specimen under thermal loading. Stress analysis was performed both experimentally and numerically, via finite-element modeling in the latter case. The results showed that strains in the track slab, in the cement-emulsified asphalt (CA) mortar and in the track bed, increased nonlinearly with the temperature increase. In the longitudinal direction, the zero-displacement section between the track slab and the track bed was close to the 1/8L section of the beam, while the zero-displacement section between the track slab and the box girder bridge was close to the 3/8L section. The maximum values of the relative vertical displacement between the track bed and the bridge structure occurred in the section at three-quarters of the span. Numerical analysis showed that the lower the temperature, the larger the tensile stresses occurring in the different layers of the track structure, whereas the higher the temperature, the higher the relative displacement between the track system and the box girder bridge. Consequently, quantifying the stresses in the various components of the track structure resulting from sudden temperature drops and evaluating the relative displacements between the rails and the track bed resulting from high-temperature are helpful in the design of ballastless track structures for high-speed railway lines.

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The Calculation of the Supporting Stress of Track Plate in Ballastless High-Speed Rail Structure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.97-98.3 ◽

2011 ◽

Vol 97-98 ◽

pp. 3-9

Author(s):

Yang Wang ◽

Quan Mei Gong ◽

Mei Fang Li

Keyword(s):

Stress Distribution ◽

High Speed ◽

Design Theory ◽

Moving Load ◽

Structure Design ◽

Track Structure ◽

Beam Model ◽

High Speed Rail ◽

Slab Track ◽

Ballastless Track

The slab track is a new sort of track structure, which has been widely used in high-speed rail and special line for passenger. However, the ballastless track structure design theory is still not perfect and can not meet the requirements of current high-speed rail and passenger line ballastless track. In this paper, composite beam method is used to calculate the deflection of the track plate and in this way the vertical supporting stress distribution of the track plate can be gotten which set a basis for the follow-up study of the dynamic stress distribution in the subgrade. Slab track plate’s bearing stress under moving load is analyzed through Matlab program. By calculation and analysis, it is found that the deflection of track plate and the rail in the double-point-supported finite beam model refers to the rate of spring coefficient of the fastener and the mortar.The supporting stress of the rail plate is inversely proportional to the supporting stress of the rail. The two boundary conditions of that model ,namely, setting the end of the model in the seams of the track plate or not , have little effect on the results. We can use the supporting stress of the track plates on state 1to get the distribution of the supporting stress in the track plate when bogies pass. Also, when the dynamic load magnification factor is 1.2, the track plate supporting stress of CRST I & CRST II-plate non-ballasted structure is around 40kPa.

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Random-Forest Machine Learning Approach for High-Speed Railway Track Slab Deformation Identification Using Track-Side Vibration Monitoring

Applied Sciences ◽

10.3390/app11114756 ◽

2021 ◽

Vol 11 (11) ◽

pp. 4756

Author(s):

Gaoran Guo ◽

Xuhao Cui ◽

Bowen Du

Keyword(s):

Random Forest ◽

High Speed ◽

Recognition Rate ◽

Operation Time ◽

Deformation Monitoring ◽

Vibration Monitoring ◽

Railway Track ◽

Ballastless Track ◽

Train Operation ◽

Track Slab

High-speed railways (HSRs) are established all over the world owing to their advantages of high speed, ride comfort, and low vibration and noise. A ballastless track slab is a crucial part of the HSR, and its working condition directly affects the safe operation of the train. With increasing train operation time, track slabs suffer from various defects such as track slab warping and arching as well as interlayer disengagement defect. These defects will eventually lead to the deformation of track slabs and thus jeopardize safe train operation. Therefore, it is important to monitor the condition of ballastless track slabs and identify their defects. This paper proposes a method for monitoring track slab deformation using fiber optic sensing technology and an intelligent method for identifying track slab deformation using the random-forest model. The results show that track-side monitoring can effectively capture the vibration signals caused by train vibration, track slab deformation, noise, and environmental vibration. The proposed intelligent algorithm can identify track slab deformation effectively, and the recognition rate can reach 96.09%. This paper provides new methods for track slab deformation monitoring and intelligent identification.

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