Design And Optimization Study On Unit Double-Block Ballastless Track On Subgrade In Area Of Large Temperature Variation

Double-block ballastless track has advantages of simple structure, convenient construction and the cost of which is lower, and this architectureapplies to some areas with a large temperature difference which can solve some potential problems at aspect of track concrete layer cracking at the time of low temperature as well as track concrete layer arching up at the time of high temperature and so on, so the adoption of unit plate is key to be successful in laying Double-block baalastless track in the area of large temperature variations. Thisthesis proceed to research design and optimization on structure of unit Double-block ballastless track that layson thesubgrade in the base of significant research achievement obtained that ballastless track at home and abroad. The main content is divided into the following several aspects.1. Discuss on design issues that unit Double-block ballastless laying on the subgrade in the area of large temperature variations.After summarizing the current situation of the Double-block ballastless track laying on the subgrade and comparative analyzing the unit and continuous architecture’s adaptability to the large temperature variation’s surrounding, the writer prefers the unit form to lay on the subgrade in large temperature variation’s area. The Double-block ballastless track laying on the subgrade in large temperature variation’s area hasn’t been intensive studied, which still has quite a few problems, including the reasonable values of design parameters at the aspect of the temperature and temperature gradient of large temperature variation’s area, the key parameter of the unit track concrete layer, the overall limit location and local deformation control as well as other details.2. Build the mechanical model of unit Double-block ballastless track laying on the subgrade in the area of large temperature variation.In order to analyze the mechanical property of major component of the architecture, we build the mechanical model of unit Double-block ballastless track laying on the subgrade in the area of large temperature variations. According to the on-site temperature testing and meteorological statistical data, we make a further analysis of design parameter, like bulk temperature, temperature gradient and so on, of the ballastless track in large temperature variation’s area. At the same time, we also simulate the probable working condition of the track’s architecturereasonable through long-term observation of the track on-site, analysis of the potential different touching ways among the track’s concrete layer, supporting layer and surface layer of subgrade.3. The selection of the parameter of the length of the track concrete layer.The length of the track concrete layer is one of key parameters of the design of ballastless track, which direct impacts mechanical property of the track concrete layer, meanwhile, which indirect impacts track’s limit location and deformation control measures. By means of analyzing the mechanical property of the unit track concrete layer at the same temperature and at the same load of a train, we find that the longer the unit track concrete layer is, the larger the stress amplitude and the longitudinal deformation at the end of the track concrete layer will be. By contrasting the crack width of the unit track concrete layer of different length and the ratio of reinforcement it needs, combined the convenience of the construction with the on-site testing proving, we bring forward the reasonable value range of the track’s parameter.4. The optimization of the ratio of reinforcement of the unit track concrete layer.The ratio of reinforcement of the unit track concrete layer is another keyparameter of track’s architecture design, which has been direct impacted by inner stress amplitude of unit track concrete layer. According to the different working state of track architecture, we make an analysis of unit track concrete layer inner stress under external load. It shows us that longitudinal stress amplitude increase progressively from the end to the centre. Therefore, we put forward the concept of multistage reinforcement at the direction of longitudinal, and provide the multistage longitudinal reinforcing plan for different length in the condition of different amplitude that temperature drop. By discussing on optimizing reinforcing bars’ diameter, and taking measures like strict controlling of the constructing temperature of the concrete, we make a further discussion on the methods of reinforcing optimization.5. The design of the measures of the limit location of unit track concrete layer.Actualizing unit track concrete layer’s limit location is the basic condition to ensure the stability of the track architecture, in which unit track concrete layer’s overall limit location and local deformation controlling are included. By contrasting many kinds of measures like anchor posts at the end of the layer, dowels in the centre of the layer and so on, we recommend unit track concrete layer adopt multi-slice dowels or steel-pipe piles in the layer to realize the overall limit location. We also provide a best scheme of dowel bar for the different length of unit track concrete layer through setting dowel bars among the layers to reinforce the integrality at the direction of transverse and vertical among the layers, and contrasting different dowel bars’ control effect, at the aspect of different diameters and numbers, to the deformation of layers’ end. According to mechanical analysis and on-site observation, moreover, analyzing the trend of development between unit track concrete layer and supporting layer, in the interest of guaranteeing to have a secure bond between rack concrete layer and surface layer.6. Design and optimization of the scheme of setting the false joint of the supporting layer.A reasonable setting of supporting layer’s false joints is the key to guide the development of supporting layer’s crack. The measure of staggered settings between traditional supporting layer’s crack and track concrete layer’s extension joint isn’t beneficial enough to the development of the cracks. Analyzed the longitudinal stress distribution characteristics of the supporting layer in different working state, we found that the location under the track concrete layer’s extension joint is the most easily part to be cracked. According to the on-site testing, it is beneficial to guide the development of supporting layer’s crack to make the extension joint and crack align.In order to avoid rainwater filters into the bottom through the joint formed by the track concrete layer’s extension joint and the supporting layer’s crack, we offer and analyze a prioritization scheme about setting a break joint between supporting layer’s creak and track concrete layer’s joint, finally, a detail design scheme emerges.On the basic of the studies on ballastless track on abroad and at home, we propose and carry out the optimization studies on Double-block ballastless track on the subgrade laying in the area of lager temperature variation. This thesis offers a base for Double-block ballastless track’s design and application in the area of large temperature variation in China. The design of unit Double-block ballastless track in this thesis is a recreation of the same track. As a matter of fact, it riches the ballastless track’s forms and expands its scope of application.