High-speed Railway Track Research Articles

Finite element steady state solution of a beam on a frictionally damped foundation under a moving load

The application of beams on foundation models subjected to moving loads in the engineering analysis of high-speed railway tracks requires a realistic characterization of the foundation behavior. In particular, the dissipative frictional character of the substructure of a railway track should be taken into account. In this paper, the steady state responses of a Euler–Bernoulli beam under a moving load on a foundation composed of a continuous distribution of linear elastic springs associated in parallel with a continuous distribution of Coulomb frictional dampers are computed. The steady state of the beam is governed by a partial differential inclusion that is semi-discretized in space, using a Discontinuous Least-Squares Finite Element Method (DLSFEM), as a system of ordinary differential inclusions, and integrated using a special implementation of the Non-Smooth Contact Dynamics method (NSCD) adapted to distributed Coulomb friction. The steady state solutions are then obtained for different values of the maximum force per unit length of the frictional dampers and for different values of the load velocity at both subcritical and supercritical regimes. It is found that the NSCD-DLSFEM produces consistent and accurate numerical outcomes in a wide range of the mechanical parameters that may be of interest in high-speed railway tracks engineering.

An Innovative Detection Method of High-Speed Railway Track Slab Supporting Block Plane Based on Point Cloud Data from 3D Scanning Technology

The dimension detection of high-speed railway track slabs is one of the most important tasks before the track slabs delivery. Based on the characteristics of a 3D scanner which can acquire a large amount of measurement data continuously and rapidly in a short time, this paper uses the integration of 3D scanner and the intelligent robot to detect the CRTSIII (China Railway Track System) track slab supporting block plane, then the dense and accurate supporting block plane point cloud data is obtained, and the point cloud data is registered with the established model. An improved Random Sample Consensus (RANSAC) plane fitting algorithm is also proposed to extract the data of supporting block plane point cloud in this paper. The detection method is verified and the quality analysis of the detection results is assessed by a lot of real point cloud data obtained on site. The results show that the method can meet the quality control of CRTSIII finished track slab and the detection standard. Compared with the traditional detection methods, the detection method proposed in this paper can complete the detection of a track slab in 7 min, which greatly improves the detection efficiency, and has better reliability. The method has wide application prospects in the field of railway component detection.

Non-linear soil behaviour on high speed rail lines

This paper gives new insights into non-linear subgrade behaviour on high speed railway track dynamics. First, a novel semi-analytical model is developed which allows for soil stiffness and damping to dynamically change as a function of strain. The model uses analytical expressions for the railroad track, coupled to a thin-layer element formulation for the ground. Material non-linearity is accounted for using a ‘linear equivalent’ approach which iteratively updates the soil material properties. It is validated using published datasets and in-situ field data. Four case studies are used to investigate non-linear behaviour, each with contrasting subgrade characteristics. Considering an 18 tonne axle load, the critical velocity is significantly lower than the linear case, and rail deflections are up to 30% higher. Furthermore, at speeds close-to, but below the non-linear critical velocity, dynamic amplification is highly sensitive to small increases in train speed. These findings are dependent upon soil material properties, and are important for railway track-earthwork designers because often 70% of the linear critical velocity is used as a design limit. This work shows that designs close to this limit may be still at risk of high dynamic effects, particularly if line speed is increased in the future.

Improved performance of the subgrade bed under the slab track of high-speed railway using polyurethane adhesive

The subgrade bed, which serves as an important foundation for supporting the slab track structure of high-speed railways, is usually filled with the graded crushed stone. The infiltration of rainwater into the graded crushed stone in the subgrade bed through cracks in the expansion joints can have a negative impact on the dynamic performance of the subgrade bed to affect the operational comfort and safety of high-speed rail travel. To prevent water from infiltrating into the subgrade bed, this study proposes a new waterproof seal layer made of the polyurethane polymer-improved gravels, which is placed on the surface of the subgrade bed. A variety of laboratory tests were performed to analyze the mixture parameters of the polyurethane polymer-improved gravels. A suitable gradation of the gravel used for the polyurethane polymer-improved gravels and its optimum composition were determined based on the test results employed in this research. In addition, two experimental models were established to investigate the dynamic and waterproofing performance of the subgrade bed with and without the new waterproof seal layer under cyclic dynamic loading. According to the model test results, the subgrade bed covered by the new waterproof seal layer displayed significantly better performance compared with that of the conventional subgrade bed when water was poured on the surface of the subgrade bed during cyclic dynamic loading.

Kinematic Measurement of the Railway Track Centerline Position by GNSS/INS/Odometer Integration

Accurate absolute measurement of existing lines is a task of fundamental importance to provide scientific basis for reconstruction. Traditional railway track survey methods in combination with classical geodetic surveying apparatus such as total stations cannot meet the requirements of surveying efficiency. Accurate, reliable and fast existing railway surveying applications call for an innovative method that can obtain high-precision, continuous and uniform railway track axis position in short time without interrupting the railway traffic. This paper provides an innovative solution to track axis surveying based on the integrated technique of global navigation satellite system (GNSS), inertial navigation system (INS) and odometer. GNSS/INS/odometer system does not depend on a high-precision track control network, which can operate in mobile surveying mode and significantly improve the measuring speed from 0.15 km/h to 5 km/h compared to conventional methods. Compared with satellite surveying methods, this solution for the measurement of existing line axis can obtain continuous and high-precision results in the absence of satellite signals. The results of field tests on the Zhengzhou-Xuzhou high-speed railway track show that the measurement errors are less than 0.6 cm and 1.1 cm in horizontal and vertical directions, respectively, and this measuring system is able to maintain high precision of 5 cm with a GNSS outage of 700 s, which can meet the accuracy requirements of China Specifications for Survey Engineering of High-speed Railway and serve visualization, assessment and design process of existing railways.

A Novel Approach of Identifying Railway Track Rail’s Modal Frequency From Wheel-Rail Excitation and Its Application in High-Speed Railway Monitoring

High-speed railway track defects such as rail corrugation, wheel polygonal wear, and rail fastener clip failure are closely related to the modal frequency of the track structure. As the operation time increases, the modal parameters of the track structure will change, and it is necessary to know what they are to diagnose the vibration characteristics. Present methods of modal analysis are limited by measuring points and excitations and cannot be used to extract the operational parameters of the railway track. This paper proposes a novel approach using wheel-rail excitations to identify the rail modal frequency from vibration monitoring data. The approach decomposes the rail acceleration after the wheel-rail excitation passes into intrinsic mode functions and extracts their instantaneous frequencies. The modal frequencies of the rail can be identified from the instantaneous frequencies. To demonstrate the feasibility of the approach, the results using the proposed approach are compared with the modal frequencies of the rail identified using the eigensystem realization algorithm. Then the approach is applied to study the influence of the number of wheel-rail excitations and the number of monitoring points on the identification results in high-speed railway ballastless track rail. The paper concludes that the proposed approach can provide a reliable solution for the identification of the operational modal frequency of track rails based on the monitoring data.

Wave propagation control in periodic track structure through local resonance mechanism

Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains. Though the track structure is characterized by obvious periodic properties and band gaps, the bandwidth is narrow and the elastic wave attenuation capability within the band gap is weak. In order to effectively control the vibration and noise of track structure, the local resonance mechanism is introduced to broaden the band gap and realize wave propagation control. The locally resonant units are attached periodically on the rail, forming a new locally resonant phononic crystal structure. Then the tuning of the elastic wave band gaps of track structure is discussed, and the formation mechanism of the band gap is explicated. The research results show that a new wide and adjustable locally resonant band gap is formed after the resonant units are introduced. The phenomenon of coupling and transition can be observed between the new locally resonant band gap and the original band gap of the periodic track structure with the band gap width reaching the maximum at the coupling position. The broader band gap can be applied for vibration and noise reduction in high speed railway track structure.

An implicit periodic nonlinear model for evaluating dynamic response of damaged slab track involving material nonlinearity of damage

In order to evaluate the vibration response of the slab track with damage more efficiently in high speed railway, a periodic nonlinear dynamic model with implicit solving method for damaged slab track is proposed involving the damage constitutive relationship of concrete under uniaxial tension. The vibration equations of the nonlinear model are discretized via the periodic spectral method in space domain, and subsequently based on the Newmark-β method and the Newton-Raphson method, the implicit dynamic integration scheme is constructed in time domain. The detailed solving procedure of the implicit dynamic integration scheme with Newton-Raphson iteration for the periodic nonlinear model is illustrated ultimately. By comparing the implicit and explicit solutions of the periodic model, the correctness and efficiency of the periodic model are verified. Furthermore, the vibration response and the evolutional rules of structural damage for the slab track of high speed railway with different strength grades for concrete slab are investigated respectively via employing the periodic model with implicit solving method.

Railway track design optimisation for enhanced performance at very high speeds: experimental measurements and computational estimations

In high-speed railway tracks, deterioration of the ballast layer and consequent impact on track geometry is the leading source of track maintenance costs. To mitigate these issues, installing under-sleeper pads (USPs) is becoming a usual strategy mainly in high-speed lines to reduce degradation rates and cut maintenance costs. However, the design of railway tracks equipped with USPs must be based on rational design processes which should take into account the impact on dynamic response of installing particular combinations of flexible track components. Within the framework of the European project Capacity4Rail (C4R), this paper shows some results obtained in a numerical model, based on a laboratory test case from CEDEX on its Track Box laboratory facility, so as to simulate and test different design solutions to upgrade track performance at very high speeds. An optimisation procedure was computed to select combinations of railpads and USPs which improves the dynamic response of the reference railway track. Results show that selected combinations of railpads and USPs lead to potential reductions of around 30% in peak vertical ballast acceleration values caused by train moving at speeds ranging from 300 to 400 km/h when compared to a reference track with no use of USPs.

Mechanical property and damage evolution of concrete interface of ballastless track in high-speed railway: Experiment and simulation

The interface damage of ballastless tracks in high-speed railway is considered as one of the most critical damage problems, however, the mechanical property and damage evolution of the concrete interface of ballastless tracks are rarely ascertained, and maintenance of the interface damage has been a heavy burden on the modern railway networks. This work aims to reveal the damage constitutive relationship and fatigue performance of the concrete interface of double-clock ballastless track based on experimental tests and simulation analysis. Firstly, by making the composite specimen composed of half track-slab concrete and half supporting-layer concrete and by designing experiment programs for the interface cracking test, the full-field evolution of strain distribution of the specimen under monotonic splitting loading is obtained based on the digital image correlation (DIC) technique, and the key parameters of a cohesive zone model for describing the interface stress-displacement relationship is determined. Subsequently, the interface damage evolution is investigated by applying cyclic splitting loads, and the interface fatigue S-N curve is acquired and validated by comparing with relevant references. It is found that the fatigue life of the concrete interface can be easily predicted with only knowing its secondary growth rate of the opening displacement amplitude. Furthermore, to elucidate the practical application of the experiment data and proposed models, the interface damage evolution of the double-block ballastless track under monotonic and cyclic temperature gradient loads are investigated, respectively. Simulation results show that much attentions should be paid to the negative temperature gradient load (below −60 °C/m) that could cause initiation of interface cracks. The proposed fatigue S-N curve enable a convenient and effective prediction for the interface fatigue damage of ballastless track with different service state under random loading cycles.

Application of Mastic Asphalt Waterproofing Layer in High-Speed Railway Track in Cold Regions

Freeze-thaw damage is a typical distress incurred in road and railway engineering in cold regions. Concrete waterproofing layer is commonly used in high-speed railway tracks to prevent the penetration of surface water, however, it cracks easily under thermal stress, especially in cold regions. Recently solutions have been proposed to increase the waterproofing layer’s cracking resistance by using asphalt layers. Nonetheless, the use of emulsified asphalt as well as dense-graded asphalt mixture were not effective enough. To improve the effectiveness, in this study, mastic asphalt was designed for application as the waterproofing layer on the subgrade surface of high-speed railway tracks in cold regions. The overall performance of mastic asphalt was preliminarily evaluated by laboratory tests, then a 200-m test section was constructed for field validation in northeastern China as part of a new high-speed railway line, and water content sensors were placed inside the subgrade to monitor the performance of the mastic asphalt waterproofing layer (MAWL). The subsequent field investigation and monitoring data during the two years operation showed that MAWL dramatically outperformed the conventional concrete waterproofing layer in terms of waterproof performance. Plenty of serious cracks were found in the conventional concrete waterproofing layer, but only a limited number of local cracks were observed in MAWL. As a result, MAWL keeps the water content of subgrade at a stable level. In addition, MAWL showed relatively high stability during the two years investigation period, and no obvious deterioration was observed in the test section.

SUBSIDENCE EVALUATION OF HIGH-SPEED RAILWAY IN SHENYANG BASED ON TIME-SERIES INSAR

Abstract. More and more high-speed railway are under construction in China. The slow settlement along high-speed railway tracks and newly-built stations would lead to inhomogeneous deformation of local area, and the accumulation may be a threat to the safe operation of high-speed rail system. In this paper, surface deformation of the newly-built high-speed railway station as well as the railway lines in Shenyang region will be retrieved by time series InSAR analysis using multi-orbit COSMO-SkyMed images. This paper focuses on the non-uniform subsidence caused by the changing of local environment along the railway. The accuracy of the settlement results can be verified by cross validation of the results obtained from two different orbits during the same period.

An explicit periodic nonlinear model for evaluating dynamic response of damaged slab track involving material nonlinearity of damage in high speed railway

For evaluating the vibration response of the damaged slab track efficiently, a novel explicit periodic nonlinear model for the damaged slab track in high speed railway involving material nonlinearity of damage is presented based on the theory of continuum damage mechanics and the constitutive relationship of concrete under uniaxial tension, where the infinite periodically supported composite beam for the track on the elastic foundation is truncated into a beam section with the length of a single vehicle by introducing periodic boundary conditions. The vibration equations of the nonlinear model are discretized into ordinary differential equations (ODEs) in space domain by the periodic spectral method, and then by applying the explicit central difference method these ODEs are solved with time-domain difference ultimately. The validity of the model is verified by the comparison of the results from the periodic model, finite element method (FEM) and the field test, and the reasonable values of the key computational parameters are recommended. Moreover, the influence of track structural parameters on the vibration response and damage evolution of CRTS II slab track of China’s high speed railway is investigated with the periodic nonlinear model. And some practical conclusions for design and construction are acquired.

Reduction of thermal effect on rail stress measurement based on magnetic Barkhausen noise anisotropy

High-speed railway and seamless track acquire quick and accurate method for stress measurement and evaluation. Magnetic Barkhausen noise (MBN) is considered appropriate to measure the stress state of rail track. But the temperature variation not only produces thermal expansion or contraction but also affects the Barkhausen jumps at the same time. Based on the theory of thermal effect on magnetic properties, the longitudinal RMS of MBN signals divided by the transverse RMS, called longitudinal and transverse ratio (LTR), is proposed as a new feature for track stress measurement to decrease the thermal effect on MBN signals. This new feature shows the same sensitivity as RMS, the traditional feature, and stability to temperature variation. With an on-site case study for verification LTR is proved robust in evaluating the track thermal stress accurately.

Influence of slab arch imperfection of double-block ballastless track system on vibration response of high-speed train

According to the structural damage characteristics of ballastless track of high-speed railway by investigation, a novel method for evaluating the influence of ballastless track of high-speed railway is presented. The dynamic model of ballastless track with damage property is established based on train-track spatial vibration system. The calculated and in situ tested results were compared to certify the model and computation program. Taking the track slab imperfections occurred in a tunnel along the real high-speed railway as an example, the influence of vibration responses of the train-track system with slab imperfections under different conditions is calculated and analyzed in comparison with normal slab. In addition, the maintenance effect on the repaired track structure is evaluated by considering the operate safety and comfort of high-speed train. It is concluded that large amplitude of slab arch imperfection results in higher acceleration of slab and car body. Therefore, train operation speed should be controlled in accordance with the safety standard such as wheel load reduction rate and derailment coefficient. In the case of low amplitude of slab arch imperfection, train operation speed should be controlled in accordance with the comfort standard such as Sperling index. The specific operation velocities were given correspondingly. Therefore, the mechanism and conclusions above can forecast intuitively in the field of track maintenance. The paper proposes a practical and valuable method for evaluating double-block ballastless track of high-speed railway.

Railway irregularity measuring using Rauch–Tung–Striebel smoothed multi-sensors fusion system: quad-GNSS PPP, IMU, odometer, and track gauge

Precise track irregularity measuring is a pivotal technique to protect dynamic safety for railway transportation applications, especially those on high-speed railways. Current methods, such as the total station-based automatic inspection systems, commonly have a high cost and are inefficient. To reduce the costs and improve the measuring efficiency, a multi-sensors fusion system consisting of multi-constellation global navigation satellite systems (GNSS)-based precise point positioning, inertial navigation system, odometer, and track gauge is proposed and is further enhanced by using the Rauch–Tung–Striebel smoother. By using this system, one not only obtains high measuring accuracy, but also obtains increased efficiency of track irregularity measuring tens of times than achieved by conventional methods. After the principle investigations, a set of high-speed railway track measuring data containing quad-GNSS (GPS, BDS, GLONASS, and Galileo) observations, laser inertial measurement unit data, odometer measurements, and track gauge data are processed and analyzed to evaluate the capability of the proposed system. The results illustrate that the proposed system, which provided approximately 0.25, 0.59, 0.65, and 0.48 mm measuring accuracy in the super elevation, horizontal, vertical, and gauge components, respectively, can be used for high-accuracy track irregularity measuring.

Interaction Mechanism of the Frost Heaving of the Filler and Skeleton Particles in a Micro-Frost-Heaving Filling Material

To address the adverse effects of the frost heaving of subgrades in regions with seasonal frozen soil on the smoothness of high-speed railway tracks, the effects of several factors—including filler, water content and external loading—on a micro-frost-heaving (MFH) filling material were studied through laboratory experiments and theoretical analysis. In addition, the interaction mechanism between the filler and skeleton particles during the frost heaving process was analyzed. The results show the following: The MFH filling material was composed of a coarse-grained skeleton, a filler between skeleton particles and the remaining unfilled voids. When the filling ratio of the filler was 0.25, the filling material underwent initial macroscopic frost heaving. An overlying load could inhibit the filling material from frost heaving. During the frost heaving process, the volume of coarse skeleton particles with high stiffness remained almost unchanged, whereas the filler expanded in volume and thus filled the remaining voids between skeleton particles and lifted the skeleton particles, resulting in macroscopic frost heaving of the filling material. When their ratio was relatively high, the remaining voids between skeleton particles had a strong absorptivity and weakened the capacity of the filler to lift the skeleton particles. The filler raised the skeleton particles, resulting in an increase in the gaps between them, which in turn facilitated the filling action of the filler. When the skeleton structure was stable, the filling action of the filler was more pronounced. The frost heaving of an MFH filling material is in fact a dynamic equilibrium process between the filling and lifting actions of the filler.

Analysis on mechanical characteristics of the polyurethane base plate for ballastless track of high speed railway

In this paper, test method is used in giving tensile strength test, elongation at break test, permanent compressive deformation, oil resistance test and dynamic and static stiffness test to the aging and non-aging polyurethane base plates, and it is used in analyzing influence of the mass ratio of bi-functional and tri- functional mixed polyethers on the relevant mechanical characteristics of polyurethane elastic base plate. The research conclusions indicate that: when using polyurethane in potting filling of the gap between track and concrete roadbed, the high-speed roadbed shall seldom show subsidence and deformation; when not giving potting filling, the whole railway ballast shall show a subsidence about 50mm after 100, 000 times of cyclic loading, and the deformation shall be very serious, which could indicate the obvious effect of the potting filling of polyurethane. When tri-functional mixed polyether has the maximum proportion, the polyurethane base plate before aging and the non-aging polyurethane base plate shall all have the maximum tensile strengths and the minimum compressive deformation of 2.91%. Along with increment of the proportion of bi-functional mixed polyether, tensile strength of polyurethane base plate shall reduce gradually, and elongation at break of polyurethane base plate shall increase continuously. 20:80 proportions of bi-functional and tri-functional mixed polyethers can be used as design standard of the polyurethane base plate.

Influence of Ballastless Track Structure on Aerodynamic Performance of Super High Speed Train

Based on the aerodynamics, this paper simulates a super high speed train with the speed of 600km/h through bridge laying plate or frame type ballastless track, analyses the influence of plate or frame type ballastless track on aerodynamic performance. Results show that the pressure at the Equipment module, the bogie and the apron is negative, and the pressure of the plate type is larger than frame type. Near the head’s bogie, the pressure of the plate type is larger than the frame type. The mediate and tail’s negative pressure of frame type is smaller than the plate type. The Super High Speed Train’s resistance of frame type is superior to the plate type. The tail’s lift of frame type is inferior to the plate type. At present, all countries in the world are strongly developing rail transportation, especially the development of high-speed rail. There are many forms of high-speed railway, such as ballasted track, ballastless track, magnetic suspension railway, etc[1]. Ballastless track structure is the main route of high-speed railway in China[2]. At present, most researches are concerned with the dynamic analysis of ballastless track of high speed railway[3-4]. The research on influence of ballastless track structure on aerodynamic performance of super high speed train has not been reported. Based on the aerodynamics, this paper simulates a super high speed train with the speed of 600km/h through bridge laying plate or frame type ballastless track, analyses the influence of plate or frame type ballastless track on aerodynamic performance.

Obtaining advantages from technology revolution: A patent roadmap for competition analysis and strategy planning

This paper aims to propose a new kind of patent roadmaps, including a roadmapping method and application directions. The patent roadmap is used to analyze patent competition and develop a patent strategy. In the patent roadmap, patent analysis, patent maps and a generic technology roadmap are used. By using these three methods in combination, two concepts, patent information and patent strategies, are linked. Further, the patent roadmap provides theoretical and informational support for companies, allowing them to learn about the current patent competition situation, and perform corresponding patent layout planning. Compared to previous research on technology and patent roadmaps, this study illustrates the patent competition situation in some industries, and provides a new method for patent strategy planning and its applications. In a case study, this paper presents the patent roadmap of the high-speed railway track (HSRT) industry, specifying the whole roadmapping process and an application in patent planning. Finally, conclusions are drawn that, in applications, the proposed patent roadmap not only plays an important role in helping companies to find new technology opportunities, avoiding duplicate R&D investments, preventing patent infringement risks, and so on, but also has important significance for guiding the overall industry development.