Papers by Keyword: Ballastless Track

Abstract: In some tunnels of railway lines located in water-rich region, due to the long-term water leakage and erosion, the foundation of railway lines showed large uneven settlement deformation, so the above concrete roadbed slabs also experienced uneven settlement accordingly. The smoothness of railway tracks diminished, and the speed of passing trains had to be limited to ensure safety. To restore the smoothness of the tracks, a dedicated polymer injection technology for quick uplift rehabilitation of uneven settlement concrete roadbed slabs was studied on site just within the specified daily skylight time (about 3 hours every day) of the railway lines. A hydrophobic polymer with low-viscosity, quick-setting and high-strength properties was used for injecting, filling and uplifting the concrete slabs in water-rich foundations. The high-precision electronic levels were adopted to monitor rising height of the tracks in real time. After rehabilitation, the filling quality of polymer injection under roadbed slabs was examined using Φ50 mm core samples and the strength of hardened polymer was verified by compressive strength test. Results indicated that the polymer could uplift the concrete roadbed slabs effectively and restore the smoothness of railway tracks accurately even in the water-rich environment. The research can provide some valuable references for quick rehabilitation of uneven settlement concrete roadbed slabs in water-rich tunnels.

Abstract: To solve the problem that there is vertical track profile irregularity with long wavelength and large amplitude a method of adjustment based on cubic spline interpolation was proposed in this paper. The key step of the method is to set up reference sleepers. This paper made an adjustment scheme for a 500-meter-long ballastless track section as an application case. An evaluation for the scheme was done by considering the evaluation indexes of regularity indexes, rail curvature and vehicle-track system dynamic responses. The evaluation result indicates that the method based on cubic spline interpolation is effective on track profile irregularity adjustment.

Abstract: At present ballastless track has been widely applied to railway line for passenger in our country, therefore it has broad prospect. Cracks in ballastless track slabs are inevitable in the construction and operation of high-speed railway. Based on comprehensive investigation of documents, and taking cracks in ballastless track slabs as the main object, systematic and deep research has been done within this paper. The main research contents are as follows: First of all, the structure characteristics of CRTSIII ballastless track in high-speed railway are briefly introduced; Secondly, the paper mostly introduces the impacts what cracks make, the characteristics of cracks and how they form. Subsequently the paper introduces what are made to prevent cracks.

Abstract: In order to achieve the online surface settlement monitoring of ballastless track,an online surface settlement monitoring system with difference image type has been established, of which the components, the preprocessing measures of images, the precise positioning methods of laser spot have also been researched. The device mainly contains a dot laser and a point-position measurement device that uses a CCD to detect the position change of the laser spot image. Any position change of the dot laser can be measured and the settlement for one point can be obtained remotely. The multi-point settlements can be obtained by using a series of such devices. Some methods such as automatic background sub-tractions and high-precision method for locating the centers of laser spots have been adopted to enhance the stability, adaptability and accuracy of the measurement system. The device has been used in some railway sites and it has the advantages of high accuracy, low-cost and easy installation.

Abstract: Dynamic response tests were developed on CRTS Ⅱslab ballastless track subgrade of Beijing-Tianjin intercity high-speed railway.The relationship between vibration response and the speed, the vertical and horizontal distribution law of vibration response along lines, the effect of axle load on vibration response were researched.Test results are as follows: The vibration displacement of the extreme value caused by a single axle load is not obvious;Train axle load significantly affects the vibration response;Despite the vertical connection between two track slab, but the end of track slab vibration response is still significantly greater than the middle and the vertical multi-storey line structure vibration response decreases rapidly along the depth;Speed has no significant effect on the vibration displacement, but vibration acceleration and vibration velocity is sensitive to speed.

Abstract: In view of ballasted-CRTSⅡ ballastless track transition section on the bridge of Beijing-Shanghai high-speed railway, the influence of track random irregularity and pier foundation settlement difference on acceleration and stability index of locomotive body are discussed by the finite element method. And then, by using the index of rail deflection gradient to describe the law of dynamic interaction, rail-wheel dynamic response, attenuation distance of locomotive body acceleration and change of sleeper pressure caused by under-rail stiffness difference are analyzed. Finally, the recommended value of reasonable length of transition section is put forwarded.

Abstract: In this paper,the functions and performances of filling layer of self-compacting concrete(SCC) in CRTS(China Railway Track System)-Ⅲ type track system were introduced. Developments of SCC including design methods and test method was described in detail. The influencing factors of workability of SCC was analysised. The trends of future development of mix proportion design methods,durability evaluation admixtures,applications were discussed.This paper also pointed that it's importance for SCC to studying the quality control methods and the application.

Abstract: As an important cushion layer, CA mortar ballastless track is crucial to the durability, safety of high-speed railway and the high-speed railway is influenced by the external environment. The regulation of temperature field evolvement of ballastless track is analyzed in this paper through a two-dimensional, transient finite element model built by ANSYS. The results show that the temperature of structure section caused by solar radiation and circumstances temperature is decreasing along depth in sunlight, and the internal temperature of structure is higher than the surface temperature at night. The integral temperature field of structure reaches the maximum at 1:00 p.m. and the vertical difference of the temperature inside the structure is also the largest, causing the most obvious temperature stress, which provides theoretical data for systematic research on ballastless track of high-speed railway.

Abstract: Creep will lead to increasing deflection of prestressed concrete girder, which may induce rails uneven, especially to ballastless tracks in high-speed railways. In this paper, two creep models, CEB-FIP90 and ACI209, were used in a finite element model to analyze influences of creep on simply supported prestressed concrete box girders which are used in high-speed railway in China. Sensitivity analysis was carried on towards curing age, secondary dead load, loading time and prestressing method on deformation of the girder. The results show creep should be controlled in engineering to ensure driving security.

Abstract: In the process of building the ballastless track of the high speed railway from Wuhan to Guangzhou, the measuring method of the CPⅢ control network has played an extremely critical role. In this article, the form layout, measuring method, precision requirements and some other contents of the high speed railway ballastless track CP Ⅲ have been proposed. It has been proved that this control network has reliable technology basis and meets the construction requirements, which is available for other similar engineering.