军区总医院深基坑支护工程设计【毕业设计论文计算说明书CAD图纸平面】
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毕 业 设 计（论 文）任 务 书1本毕业设计（论文）课题应达到的目的： 基坑支护体系是临时结构，安全储备较小，具有较大风险。在实际工程中，每个基坑的平面尺寸、开挖深度、水文地质条件和周围环境都不一样，为了解决复杂的基坑工程问题，需对具体基坑支护结构进行设计。考虑工程周边环境及地质条件，选择适合的支护形式。应用朗肯土压力理论，用等值梁法计算支护结构内力，确定等设计参数，根据计算成果，绘制基坑支护设计施工图。本基坑设计遵循安全可靠、经济合理、方便施工的原则，完全能够满足基坑土方开挖过程中支护结构本身和周边环境安全保护的要求。2本毕业设计（论文）课题任务的内容和要求（包括原始数据、技术要求、工作要求等）： 1、主体结构参考建设单位提供的该工程的主体结构建筑平面图、总平面图及招标文件。（1）本工程主体结构0.000相当于黄海高程+10.000m，本设计除特别说明外均采用主体结构相对标高。（2）主体结构：主体为地下二层，地上两栋26层高层建筑，框架剪力墙结构。负一层底板板顶标高为-4.50m，负二层底板板顶标高为-9.60m。（3）基坑规模：地下室范围东西方向约105m,南北方向约72m，基坑面积约7000m2左右，基坑周长约350m。（4）基坑挖深：周边自然地面相对标高为-0.50-0.80m，基坑开挖深度详见表。2、设计资料 （1）地质资料:根据南京勘察工程公司提供的勘察报告，该场区的工程与水文地质条件如下：基坑开挖深度一览表区段自然地面相对标高(m)坑底标高（m）开挖深度（m）西侧、北侧-0.8-12.812.0东侧、南侧-0.5-12.812.3注：本设计坑底标高为建设单位招标文件提供标高，未考虑基坑内部坑中坑位置的影响问题，待建设单位提供主体结构施工图后，再提供坑中坑部位的处理措施及支护体系的调整。（2）场地地形、地貌拟建场地位于南京市中山东路南侧、解放南路西侧、中山东路520号内。场地原为15层房屋，现已拆迁，拆迁后地势较为平坦，勘探孔口高程9.9210.38m。场地地貌单元属于秦淮河漫滩相地貌单元。（3）岩土层分布及分布特征根据勘察揭示的土层结构，基坑开挖影响深度范围内的地层如下：-1层杂填土：杂色，以碎石、砖、生活垃圾等组成，土体松散，分布均匀。该层层厚0.303.20m，层底埋深0.303.20m。-2层素填土：灰灰黄色，软可塑，呈稍密状态，主要成分为粉质粘土，含碎石等，分布不均匀，土质不均，堆积年限大于10年，基本完成自重固结。层厚0.203.90m，层底埋深2.104.60m。-1层粉质粘土：灰黄黄褐色，湿，可塑状态，中压缩性，含铁锰质氧化物，土质较均匀切面较光滑，无摇震反应，韧性中等，干强度中等，场区普遍分布，厚度变化不大。层厚0.903.90m，层底埋深4.107.10m。-2层粉质粘土淤泥质粉质粘土：灰色，湿饱和，流软塑状态，局部含腐殖质，部分地段夹薄层粉土，土质不均，稍有光泽，稍有摇震反应，韧性中等，干强度中等，全场区均有分布，厚度大。层厚12.5017.90m，层底埋深18.30 22.60m。-3层粉质粘土：灰色，湿，可塑状态，中偏高压缩性，含腐殖质，分布不均，只在场区的西北角见到。切面较光滑，无摇震反应，韧性中等，干强度中等，厚度变化大。层厚1.6010.50m，层底埋深22.9032.00m。-4层粉质粘土：灰黄褐黄色，稍湿，可硬塑状态，中压缩性，切面较光滑，无摇震反应，韧性高，干强度高，场区均有分布，厚度变化不大，层厚0.706.40m，层底埋深24.0034.40m。（4）水文概况拟建场地对基坑开挖有影响的浅部地下水属于潜水，含水层为-1、-2及-2层土中，水量较小，地下水位最后要受大气降水及地表水影响。另微承压水水位于层土中，水量较大，但对本工程基本无影响。潜水最高地下水位按整平后地面下0.5m考虑。3、技术要求和工作要求：（1） 基坑支护设计资料收集：1）场地岩土工程勘察报告，基坑支护设计参数。2）建筑红线、施工红线的地形平面图及基础结构设计图；建筑场地及其附近的地下管线、地下埋设物的位置、深度、结构形式及埋设时间等。3）基坑附近的地面堆载及大型车辆的动、静荷载情况。4）临近的已有建筑物的位置、层数、高度、结构类型、完好程度。已建时间以及基础类型、埋设深度、主要尺寸、基础距基坑的净距离等。5）基坑周围的地面排水情况，地面雨水与污水、上下水管排入和漏入基坑的可能性。6）已有相似基坑支护的经验性资料。（2）基坑支护方案和降水方案的选择，确定基坑支护围护结构布置，止水、降水技术方案，基坑开挖、监测方案。基坑支护计算断面的确定。（3）按确定的计算断面分别进行基坑支护围护结构、支撑体系设计计算，降水方案计算，基坑稳定性验算，抗隆起验算。（4）要求编写完整的基坑支护设计报告。（5）按照工程设计和施工要求绘制基坑支护设计相关图纸。毕 业 设 计（论 文）任 务 书3对本毕业设计（论文）课题成果的要求包括图表、实物等硬件要求： 一、文字部分：1、设计说明书、结构计算书；2、外文资料翻译（英-汉），设计摘要翻译（汉-英）。二、图纸部分基坑支护设计方案说明、平面布置图、支撑布置图、降水方案布置图1张； 基坑支护设计结构剖面图、支撑大样图、降水大样图1张4主要参考文献： 1.建筑地基基础设计规范 GB50007-20122.岩土工程勘察规范 GB50021-20133.南京地区地基基础设计规范DB32/112-95,20124.基坑工程手册 候学渊，刘建航 中国建筑工业出版社，20105.建筑基坑支护技术规范 JGJ120-20136.混凝土结构设计规范GB50010-20127.岩土工程手册 中国建筑工业出版社，2010毕 业 设 计（论 文）任 务 书5本毕业设计（论文）课题工作进度计划：起讫日期工作内容2015-12-22015-12-20毕业设计任务布置、熟悉工程情况、收集资料，攥写开题报告，翻译专业文献资料。2015-12-212016-1-12收集资料、确定基坑支护设计方案，完成开题报告。翻译专业文献资料。2016-1-132016-2-29土压力、支护结构、支撑设计计算，理正软件校核手算结果。打印专业文献翻译。2016-3-12016-4-30止水帷幕、降水方案设计计算。基坑支护设计计算书编写、打印，基坑支护平面图、支护结构图纸绘制。2016-5-12016-5-5基坑支护设计计算书图纸校对、打印，上交毕业设计成果。毕业设计成果包括： 1任务书；2开题报告；4设计报告；5图纸；6专业文献翻译及原文2016-5-62016-5-10毕业设计报告成文，包括计算书和图纸。2016-5-112016-5-14制作多媒体答辩材料，准备答辩。所在专业审查意见：通过负责人： 2015 年 12 月21 日 译文题目： 高速铁路无砟轨道的设计理论的发展 外文原文：Advances in design theories of high-speed railway ballastless tracksAbstract: The design theories of the ballastless track in the world are reviewed in comparison with the innovative research achievements of high-speed railway ballastless track in China. The calculation methods and parameters concerning train load, thermal effect, and foundation deformation of high-speed railway ballastless track, together with the structural design methods are summarized. Finally, some suggestions on the future work are provided.Key words: high-speed railway; ballastless track; design theory1. IntroductionStructure forms and design theories of ballastless tracks vary across the world due to the different development backgrounds. In Japan, the slab track was typically laid on the solid foundation such as a bridge or tunnel at first, and then gradually developed to the soil subgrade afterwards. It adopts the unit design that takes into account the effect of train load. The German ballastless track was first laid on the soil subgrade and then on the foundation of bridges and tunnels. Its continuous structure involves the consideration of thermal effects. The early ballastless track in China was mainly laid in tunnels with the chief concern being the influence of train load. With the increasing application of ballastless track, a relatively general design theory and a structural system have been gradually formed after the innovative research with high-speed railway ballastless track.This paper reviews the calculation methods and parameters as well as the structure design procedures, and briefly introduces the advance in the design theories, of ballastless track based on the innovative research achievements in China. Finally, some suggestions on the future work are provided, including fatigue properties under the coupling action of train and temperature load, durability, long-term dynamic properties, and maintenance mechanics of the ballastless track.2. Overview of ballastless track design theoriesIn the design of Japanese slab track, the train load effect is a primary concern. Using the elastic design method, the security during the manufacturing, hoisting, and constructing of the slab track is maximized. As seriously damaged CA mortar at the slab corner and the slab warping caused by temperature gradients emerged, the uneven support caused by warping is considered in the analysis 1. In the baseplate design, in accordance with the limit state method, the train load and the subgrades uneven settlement are considered together with the influence of weather conditions, concrete contraction, and construction.German developed its ballastless track by borrowing the design concept and method of pavement engineering 2. Most has longitudinally continuous structure, and temperature load and concrete contraction are the main factors to be considered in the design. The reinforcement is located near the neutral axis and does not bear the train load. The effect of train load and temperature gradient is resisted by the rupture strength of the concrete.In China, the early monolithic roadbed track, whose structure design mainly considers the train load, was applied in the tunnels with good foundation condition and little temperature variation. The structural design of the Suining-Chongqing railway took into account the effect of uneven foundation deformation and temperature load 3-4. Following systematic research on the ballastless track, the design theory based on the allowable stress method was created with full consideration of train load, temperature, and foundation deformation effect.In general, the design theory of ballastless track in different country was relevant to its own construction environment and structure evolution. The design theory proposed in different periods could meet the construction requirements for different types of ballastless track.3. Calculation of train load stressThe track supports the train load and guides the vehicle operation. The calculation of train load stress must be considered in the ballastless track design. The elastic foundation beam model 5-6 is mainly used for calculation of the load stress in the traditional track structure. The model can be solved using the multilayer composite beam theory on the elastic foundation 7-10 according to the complexity and analysis requirement of the track structure. In Germany, however, the Eisenmann theory 11-13 was adopted to calculate the stress of the rail structure under the train load. In this theory, rail is regarded as an infinite beam on the elastic foundation to calculate the support reaction of the fastener; the multilayer structure is translated into a monolayer one according to the connection status of the structural layer, and then the internal force and displacement of the converted monolayer structure under the action of fastener force is calculated using the infinite beam on the elastic foundation and Westgaards stress function.To sum up, the main components are treated as flexural members in the train load design of ballastless track in China and Japan. This is because the ballastless track design was originally developed based on the traditional design methods for ballast track that put an emphasis on simulation of the force properties of main components and the generality of analysis method. In Germany, however, the design theory and parameters selection of ballastless track were developed from the experience of highway concrete pavement design; thus, its structural difference in ballastless track can also be attributed to heritance of the traditional design theory.In accordance with the structural characteristics that the rail and the sleeper are cross-supported on the elastic foundation in the ballast track, the cross beam model on the elastic foundation 14-15 was developed on the basis of the elastic foundation beam model, and can also be used for the stress calculation of the ballastless track 16 once the values of the model parameters are determined. Thanks to the development of the computing technology, the solid finite element model 17-19 can be employed to obtain the particular stress state inside the ballastless track structure.As the major supporting structure of the ballastless track, the track slab (or bed slab) and baseplate (or supporting layer), whose deflections under the train load are far smaller than their thicknesses, have a far smaller size in the vertical direction than in the longitudinal or lateral direction. This feature conforms to the structural characteristics of the elastic plate. Consequently, the elastic plate 20 is generally adopted for simulation and analysis of the supporting structure of ballastless track. The rail, a slender structure, is reasonably simulated by the beam model, while the fastener and the intermediate elastic layer, as well as the foundation below, are simulated with different kinds of springs. As a result, a beam-plate model of ballastless track on elastic foundation 21-23 is built as shown in Fig. 1.The load stress of the track slab (or bed slab) and the baseplate (or supporting layer) in the longitudinal and lateral directions can be obtained by exerting a vertical train load on the rail. This avoids the calculation in the longitudinal and lateral directions separately in the multilayer elastic foundation beam model. Moreover, the computational accuracy 7 is higher than that via the composite beam model or the cross beam model, and the computing workload is less than that via the solid finite element model.The design wheel load of the Japanese slab track takes into consideration the wheel load variation due to wheel tread damage and tolerates three times the static wheel load. In fatigue checking, the allowable wheel load is 1.45 times the static wheel load. On the basis of the allowable value of the derailment coefficient, the design lateral force was determined, and the lateral force for fatigue checking takes half of the design lateral force. In the Germany ballastless track design, the load takes the UIC71 with the dynamic coefficient of 1.5 and the unbalance loading coefficient of 1.2. In China, the dynamic coefficient is based on the results of dynamic tests and simulation calculations of the ballastless track, and the design wheel load can be three times the static wheel load. Based on the design parameters and operation conditions of the ballastless track on the passenger dedicated line (PDL) in China, the coupling dynamics of train and track system is applied to the statistic analysis. Considering the construction and maintenance conditions of the ballastless track in China, it is suggested that the constant effect train load be up to 1 .5 times the static load 24.The Winkler foundation is used to support the ballastless track, and the diameter of the bearing plate has a significant influence on the foundation coefficient. The smaller the diameter, the larger the foundation coefficient 1. However, when the diameter D is not less than 76 cm, the change in the diameter has little influence on the foundation coefficient. As for the ballastless track, the supporting area of the track slab or the supporting layer is relatively large. Thus, for simplicity, the trial value of the bearing plate with a diameter of 76cm, namely k76, can be used for calculations. When the sub- grade compaction capacity is represented by the deformation modulus, the layered elastic system mechanics 3 can be applied to analyze the displacement of the subgrade surface with the even load of the rigid bearing plate; thus, deducing the supporting rigidity of the sub-grade surface 25.Within every bearing layer of the ballastless track, the substructure is generally weaker than the upper structure, and may readily crack under the train load if plain concrete or cement stabilized materials are applied. Once cracking, the bending moment is not readily transferred at the crack location, resulting in a reduction in the entire rigidity and the modulus of elasticity. There- fore, the reduced elastic modulus is used for calculation 26. As for the reinforced concrete structure, the reinforcement is helpful to improve the flexural rigidity of the structural layers. However, due to the possible cracking, the transmission of the bending moment at the cracked location may be weakened. Consequently, only the concrete elastic modulus is used for calculation, without consideration of the influence of the reinforcement and crack.4. Calculation of temperature stressThe ballastless track is exposed to the atmosphere. With changes in external temperature, the temperature in every structural layer will vary. Once the deformation of the ballastless track due to the changing temperature is restrained, the temperature stress will occur inside the structure. The ambient temperature variation with an effect on the ballastless track includes the yearly temperature variation and daily temperature variation. In addition, the contraction of concrete will cause distortion, which is equivalent to decreasing the temperature load acting on the concrete.The design of the continuous ballastless tracks represented by Rheda, Zblin, and Bgl in Germany attach great importance to the temperature effect. In order to limit the width of the temperature cracks within the admissible range and maintain the state of incomplete cracks 27, the ratio of reinforcement in the slab should reach 0.8%0.9%, according to the German Ballastless Track Design Specification. As a result, the width of cracks is limited within 0.5mm. From the viewpoint that the sum of the minimum stress of the reinforcement with the slab cracking and the bending stress increment under the dynamic load must be less than the reinforcement fatigue limit to guarantee the service life, it is supposed that the longitudinal ratio of the reinforcement must be larger than 1.0%, so as to meet the demands of crack width and service life.The Japanese slab track design adopts unit structure, and temperature variation has little influence on the track slab. Thus, temperature effect is not considered in the design. Nevertheless, warping displacement of the track slab is found in tests, where the track slab is in a state of being incompletely supported. Therefore, to address the variation properties of the track slab due to temperature, a series of theoretical and experimental research has been conducted 4.As for the continuous slab structure, under the action of concrete contraction and decreasing temperature, concrete may easily crack, causing a stress redistribution of the reinforcement and concrete inside the slab. In order to guarantee security and utility, it is necessary to control the reinforcement stress and crack width.The continuous slab shows different stress and variation properties at various tension stages. Before the concrete cracks, the concrete deformation is coordinated by the reinforcement. When the tensile stress of the concrete reaches its tensile strength, it will crack and stop working, which leads to the bond damage adjacent to the cracks. At this moment, the plain section hypothesis does not fit any more, and the reinforcement at the crack location bears all the axial force. When the axial force increases to the yield strength of the reinforcement, the concrete is cracked severely without bearing the tension. All the axial force is born by the reinforcement, such that the reinforcement yielding becomes the limiting condition of the slab in tension. The cracking axial force of the continuous slab depends on the tensile strength of the concrete and the sectional area of the slab. The amount of reinforcement has little influence on the cracking axial force, while the ultimate bearing capacity completely depends on the yield strength and the area of the reinforcement. In order to avoid cracking, the minimum ratio of reinforcement of the continuous slab should be specified.The cracking in the continuous slab go through two phases: incomplete cracking and complete cracking. At the stage of incomplete cracking, the amount of cracks increases with the increasing load, and the maximum crack width remains basically unchanged. At the stage of complete cracking, the number of cracks remains unchanged, while its width increases with the increasing load. In order to limit the crack width, the cracking should be controlled at the stage of incomplete cracking. In the cases of incomplete cracking, the maximum temperature force inside the slab depends on the tensile strength and the sectional area of the concrete. The temperature force calculated with the design tensile strength is regarded as the common temperature force (main force). And the temperature force calculated with the standard tensile strength is taken as the maximum temperature force for checking in design. Refs.28-29 elaborated the different expressions of fracture interval, cracking width and reinforcement stress at different stages of cracking, and the relevant design measures have been put forward.As for the unit bed slab structure, the temperature force of the slab is influenced by the longitudinal resistance of the fastener at the top and the frictional resistance at the bottom, as well as the displacement limitation of the convex plate. The classification of the unitary and continuous structure depends on whether the temperature force leads to the full-section cracking of the slab.5. Calculation of warping stressThe external environment will affect the temperature and humidity of the concrete slab. The influence of external environment gradually weakens with the depth from slab surface. The uneven distribution of temperature and humidity inside the slab leads to its warping deformation. When the deformation is restrained by the bottom friction, dead load, stop blocks, and train load, the warping stress occurs.According to the German railway code, it is hypothesized that the slab in the vertical direction has a linear temperature gradient of 50 /m. In the temperature field test of the ballastless track on Suining-Chongqing railway, the temperature gradient 30 of the track be- fore laid is about 52.668.4 /m and the temperature gradient of the slab track in the longitudinal direction on the Jialingjiang bridge is approximately 4080/m 31, with a large dispersion, but all larger than that of 50 /m in Germany.In terms of geography and climate conditions, China has severely cold areas, cold areas, and temperate areas. Referring to the recommended value of the temperature gradient in the field of highway pavement, in consideration of the structure characteristics of the ballastless track, we advise that the maximum positive temperature gradient of the uppermost structure of the ballastless track in China be 8085 /m, 8590 /m and 90 95 /m for severe cold area, cold area and temperate area, respectively, and that the temperature gradient distribute linearly in the vertical direction. The effect of temperature gradient can be neglected in the substructure. The negative temperature gradient can be half the maximum positive temperature gradient.According to the statistical data about the temperature and the temperature gradient variation in Germany, studies have been conducted to analyze the slab stress state under the action of the temperature gradient, especially the slab with smaller lateral size whose warping deformation is not restrained completely. The calculation model with discontinuous supporting was utilized to calculate the warping stress 32 under the action of dead load and temperature gradient.The warping stress and displacement of the slab track in different constraint conditions were analyzed by finite element theory. The results show that the stronger the restraint acting on the track slab, the more the warping deformation is resisted, and the closer the warping stress in the slab track to that of an infinite slab. The restraints acting on the track slab include the track dead load, the restraint of the continuous long rails, and the train load acting on the rails. Because of the large supporting coefficient in the ballastless track supporting system, the loading restraint of the track slab, due to the limitation of the loading magnitude and position, shows many differences. For convenience, no matter for the unitary or the continuous structure, the warping stress of the ballastless track in the longitudinal or lateral direction is calculated in accordance with the infinite slab.6. Calculation of foundation deformation effectBallastless track will be influenced remarkably by the large rigidity of the track slab or the bed slab once uneven deformation occurs at the foundation.In the Japanese slab track base design, the maximum settlement displacement () occurs at the mid-point and at the ends of the baseplate with the half-wave sinusoid of =20 mm at the service and fatigue state, together with that of =30 mm at the ultimate state. Based on the deformation relevance, the rigidities at different locations of the settlement area with an interval of 5 m are calculated to ensure the settlement of the baseplate under the dead load reaches the designed uneven settlement. Then the additional bending moment 33 due to foundation deformation of the baseplate is calculated. Germany has a concept of “zero settlement” that uneven settlement must not occur. Thus, there is no need to consider the uneven settlement effect in design. Although high-speed railways have developed rapidly in China, uneven settlement is also inevitable at the sub-grade-bridge transitional sections and high embankment. In order to ensure the proper operation of ballastless track, the influence of uneven settlement of foundation should be considered in the design of ballastless track in China.Because of the large rigidity of ballastless track, when there is uneven settlement, the slab will have the same deformation as the foundation, which can be viewed as a forced displacement of the slab structure. In this case, the bending moment of the slab under the action of foundation deformation equals to the product of its flexural rigidity and the uneven deformation curvature.7. Design of ballastless track structureThe bearing structures of the ballastless track mainly include plain concrete, reinforced concrete, and prestressed reinforced concrete. The plain concrete structure is usually applied to the tunnels with good foundation and small ambient temperature variation. In this case, the slab will not crack 34 under the action of train load and environmental factors. Under the common foundation conditions, the slab may readily crack with the influences of foundation deformation, train load, and environmental factors. Thus, it is necessary to add reinforcements to limit the crack development. As for the continuous reinforcement concrete slab, because the temperature stress is the main influencing factor, reinforcements are laid near the neutral axis to limit the crack width and crack interval of the track slab. For the sections with severely weak foundations, the bending moment in the slab is usually large. In order to limit the crack width, we need to thicken the slab or improve the foundation, which results in high costs. In that case, placing reinforcements in top and bottom layers can help the track slab bear more bending moment 35-36. To limit the crack width and improve the structure durability, steel fiber concrete has been increasingly used in the ballastless track structure 37-38. In cold areas, prestressed reinforced concrete structure is often adopted for decreasing the freezing injury.The allowable stress method and the ultimate state method are generally utilized in the concrete structure design. As the Japanese track slab was designed as reinforced concrete structure originally, the allowable stress method is adopted provided that the track slab concrete under the action of bending moment conforms to the hypothesis of plane mechanism, while the tensile stress of the concrete in the tension zone is negligible. The allowable stress of the reinforcement depending on the repeated loading times varies with different design wheel load and structure types. In the cold areas, anti-freezing measures should be taken. Considering factors such as construction and costs, the prestressed reinforced concrete structure 39 designed by partial limit state theory is applied.For the German ballastless tracks like Rheda and Zblin, the longitudinal reinforcements are placed in the continuous slab for the purpose of controlling the crack types and width. The width of the slab is determined by the Westergaards stress equations and the allowable compressive stress of the subgrade surface. Determination of the slab thickness follows the principle that the stress caused by temperature gradient and load is less than the flexural strength of the slab concrete. The supporting layer is composed of plain concrete probably with cracks or is the hydraulic supporting layer structure. The load stress should be checked within the permissible limit to determine the modulus of elasticity of the supporting layer.Ballastless track, laid on the elastic foundation under the long-term repeated action of train load and environmental change, is of band structure distinct from the structures like bridge and building. In order to ensure its high accuracy and high stability, the rail structure is required to work in an elastic condition under the action of train load and surrounding factors. Therefore, we suggest that the ballastless track structure design adopts the allowable stress method for the innovative research of high speed railway in China.During the design, it is assumed that every plane cross-section remains a plane under the action of the bending moment. The normal stress of the concrete in the compression zone takes a triangle pattern, the tensile strength of the concrete in the tension zone is neglected for the reinforced concrete components, and the normal stress of the concrete in the tension zone also takes a triangle pattern for prestressed reinforced concrete components. Under the action of axial force, the temperature stress of the continuous ballastless track, which may cause cracking, is resisted by the reinforcement, and the plane assumption is invalid.Because the method for calculating the load effect, especially under the action of bending moment is different from the calculation model for structure design, a correction factor is introduced to eliminate the difference in the obtained results. The specific design flow for the ballastless track structure is shown in Fig. 2.As for the unit ballastless track, the reinforcement is mainly based on the load bending moment and the effect temperature force is negligible. For the continuous ballastless track, concrete contraction and temperature decreases are the main factors influencing the reinforcement. The load combinations for the different kinds of ballastless track on diverse foundations are listed in Table 1.The daily temperature has a periodic variation, leading to a periodic variation in temperature stress and warping stress. Nevertheless, the maximum temperature gradient and the maximum temperature force do not appear everyday. Especially for the continuous ballastless track, the maximum temperature force only occurs at the critical state when a new crack appears. When the crack is stabilized, the temperature force is mostly less than the maximum temperature tension. Therefore, the maximum temperature tension is unlikely to appear in the continuous ballastless track, and it can be regarded as a kind of load combination and checked independently.The subgrade of PDLs is required to be designed and constructed under the concept of “zero settlement”. However, uneven settlement is easy to occur at the transitional section between subgrade and the structures such as bridge, tunnel or culvert. And the probability of the uneven settlement within a small range occurring to common sections is quite low. Therefore, the uneven settlement of subgrade should be combined as an additional force with a low probability of occurrence. Under the train load, a bridge has bending deformation which coincides with the train load. Consequently, the bridge bending deformation should be combined as the main force the same as the train load.Fig. 2 Design flow for the ballastless track structureTable 1 Suggested load combinations for different types ofballastless tracksAccording to the load combinations shown in Table 1, one should decide whether the edge stress of the supporting layer in the ballastless track exceeds its cracking stress. If the edge stress is lower than the cracking stress, then the supporting layer of the concrete will not crack, and reinforcement is unnecessary or should be placed in accordance with the structure. If the edge stress is higher than the cracking stress, then the supporting layer will crack. Especially for the continuous ballastless track, full-section cracking is likely to occur. At the moment, all the concrete in the tension zone at the cracking location under the action of bending moment stops working, and all the tension is resisted by the reinforcement. Nevertheless, the concrete between two cracks in the tension zone is still functioning, which leads to the variation of sectional flexural rigidity and neutral axial. The flexural rigidity of the cracked slab is decreased sharply. A thinner slab with a higher concrete grade will have a smaller flexural rigidity after cracked.The flexural rigidity used for the load stress calculation is the one with the supporting layers full section sharing the stress. However, during the design the concrete in the tension zone is supposedly out of operation completely, from which some error will occur and there is a need for revision.According to the elastic foundation beam theory, the bending moment of the foundation beam under the concentrated load (train load) is directly related to the coefficient of elasticity of the foundation and the flexural rigidity of the foundation beam. The bending moment of the foundation beam is directly proportional to the 1/4 power of its flexural rigidity. Similarly, the bending moments of the slab caused by temperature gradient and foundation deformation are directly proportional to its flexural rigidity. Thus, the correction factor of the bending moment caused by train load, temperature gradient and foundation deformation can be obtained.8.Conclusions and suggestionsBallastless track, with the merits of good ride comfort, high stability and little maintenance, has become the main type of the rail structure. The design concepts of the ballastless track are different in different countries: the factors considered in design and the calculation methods vary greatly with each other. This paper has summarized and analyzed calculation and design methods for ballastless track in the world. Based on the re-innovation research results of the ballastless track in China, relatively general design concepts and methods for ballastless track were put forward tentatively, which guided the design of ballastless track on the Suining-Chongqing test section, the Wuhan-Guangzhou passenger dedicated line, the Lanzhou-Urumchi No.2 double line, as well as the reference diagram design of the slab track and the double block track.Although, a type of structure with little maintenance, the ballastless track has many conditions during operation. Therefore, the design theory of ballastless track still needs further study. The future work may involve the following:(1) Research on the fatigue properties under the coupling action of train and temperature load. Train load and temperature load are two kinds of loads repeatedly acting on the ballastless track. The statistical characteristics of train load and temperature load, especially the fatigue properties under different loads and their coupling action, should be studied to provide a basis for predicting the fatigue life of ballastless track.(2) Research on the durability of ballastless track. The ballastless track is a composite structure composed of many kinds of materials. Under the combined action of environment and train load, different kinds of materials have different degradation curves, and the damage in one component will influence the durability of the whole structure. Therefore, a systematic method should be applied to the durability research of ballastless track, to realize a design concept of little maintenance.(3) Research on long-term dynamic properties. Under the long-term combined action of train load induced vibration and natural environment, the function of the components of ballastless track is likely to degrade gradually. Consequently, the dynamic characteristics of ballastless track, and the safety and stability of train will be influenced. An analysis model of ballastless track with damage should be established for research on the long-term dynamic properties of ballastless track.(4) Research on maintenance mechanics. At the beginning of the construction of ballastless track, some conditions have already occurred because of the errors in design and construction. Thus far, there is lack of a systematic, intensive study on the causes of diseases and the countermeasures. The intensive study on disease mechanism, maintenance standard, maintenance time, maintenance method, and the influence of maintenance on track and train will lay a good foundation for the maintenance work of ballastless track.中文翻译：高速铁路无砟轨道的设计理论的发展摘要：世界上的无砟轨道设计理论与我国高速铁路无砟轨道的创新性研究成果进行比较。对列车荷载、热效应，以及高速铁路无砟轨道地基变形，和结构设计方法的计算方法和参数进行了总结。最后，为今后的工作提供了一些建议。关键词：高速铁路；无砟轨道；设计理论1.引言结构形式和无砟轨道设计理论由于世界各地的不同发展背景而不同。在日本，平板轨道通常是在一个坚实的基础上，如桥梁或隧道，然后逐步发展到土路基。它采用了单元设计，该设计考虑列车荷载的影响。德国无砟轨道首次次用于土路基，然后用于桥梁和隧道的基础。它的连续结构涉及热效应。我国由于主要关注的是列车荷载的影响，早期的无砟轨道主要用在隧道上。随着无砟轨道的应用越来越广泛，相对一般的设计理论和结构体系逐渐在高速铁路无砟轨道的创新研究后形成。本文介绍的计算方法和参数以及结构设计方法，并简要介绍了基于在中国的创新研究成果的无砟轨道的设计理论的发展。最后，给出了对未来工作的一些建议，包括在耦合作用和温度荷载作用下的列车的疲劳性能，耐久性，长期动态特性，和无砟轨道的养护力学。2.无砟轨道设计概述在日本板式轨道设计中，列车荷载效应是首要关注的问题。他们采用弹性设计方法，在制造、吊装、施工板式轨道时的安全性进行了最大化。由于在板坯角砂浆的严重损坏和温度梯度出现造成的板坯翘曲，他们在分析中考虑了翘曲引起的不均匀的支撑1。在底板的设计中，按照极限状态的方法，他们考虑了列车荷载作用、路基的不均匀沉降和天气条件、混凝土收缩及建设的影响。德国借助设计理念和路面工程的方法发展了它本国的无砟轨道2。使最具有纵向连续结构，温度荷载和混凝土收缩是设计中要考虑的主要因素。钢筋位于中性轴附近，不承担火车荷载。混凝土的断裂强度抵消了列车荷载和温度梯度的作用。在我国，早期的整体式路基轨道应用有在良好的基础条件和小的温度变化条件下的隧道中，其结构设计主要考虑列车荷载。睢宁重庆铁路的结构设计综合考虑了地基不均匀变形和温度荷载的影响3-4。下面是对无砟轨道系统研究，基于许用应力法的设计理论充分考虑了列车荷载，温度和地基变形效应的影响。一般来说，不同国家的无砟轨道设计理论有关自身的施工环境和结构的演变。不同时期提出的设计理论满足不同类型无砟轨道的施工要求。3.列车荷载应力计算轨道要承担列车荷载并引导车辆运行。在无砟轨道的设计中必须计算列车荷载应力。弹性地基梁模型5-6主要用于传统轨道结构的荷载应力计算。根据轨道结构的复杂性与分析要求，采用弹性地基上的多层复合梁理论7-10可以解决该模型。但是，德国的Eisenmann的理论11-13是计算在列车荷载作用下轨道结构的应力。该理论把轨道看成是弹性基础上的无限长的梁，用来计算紧固件的承受反应；根据结构层的连接状态，多层结构转化为一个单层结构，然后转换层结构在紧固力作用下的内力与位移可以用弹性地基上无限长梁模型和Westgaard应力函数计算出。综上所述，在中国和日本的无砟轨道列车荷载设计中受弯构件是主要部分。这是因为无砟轨道的设计最初是由压载轨道的传统设计方法发展而来，这种方法重点是对主要部件的受力特性和分析方法的通用性的模拟。然而，在德国，这无砟轨道的设计理论和参数选择是由公路水泥混凝土路面设计经验发展而来；因此，无碴轨道的结构差异也是因为传统设计理论的继承。按照钢轨和轨枕在压载轨道的弹性基础上交叉支承的结构特点，弹性地基上的十字梁模型14-15是在弹性地基梁模型的基础上发展的，一旦模型参数的值确定了，它也可用于无砟轨道的应力计算16。得益于计算技术的发展，固体有限元模型17-19可以用来获得无碴轨道结构内的特定的应力状态。作为无碴轨道的主要支撑结构，轨道板（或面板）和底板（或支承层）在垂直方向上的尺寸比在纵向或横向上的尺寸更小，其在列车荷载作用下的挠度远比它的的厚度小。此特性符合弹性板的结构特点。因此，厄尔尼诺弹性板20一般采用无碴轨道支撑结构的仿真分析。一个细长的结构铁路可以用光束模型合理地模拟，而紧固件和中间弹性层以及下面的基础用不同种类的弹簧进行模拟。因此，一个弹性地基上无砟轨道的梁板模型21-23建立如图1所示。图1.无砟轨道的梁板式弹性地基纵向和横向的方向上的轨道板(或面板)和底板(或支承层)的荷载应力可以由施加一个垂直于车轨的负载获得。这样就避免了多层弹性地基梁模型中纵向和横向方向的分别计算。此外,计算精度7要高于复合梁模型或横梁模型的计算精度，计算工作量要小于可靠的有限元模型的计算工作量。日本板式轨道的轮载荷设计考虑了车轮踏面损伤产生的轮载荷变化，可以承受静态轮载荷的三倍。在疲劳检查中，容许轮载荷是静态轮载荷的1.45倍。在脱轨系数允许值的基础上，确定了设计的侧向力，并取疲劳验算的侧向力为设计侧向力的一半。在德国无碴轨道的设计中，负载取uic71，动力系数为1.5，偏载系数为1.2。在中国，动态系数基于动态试验的结果和无砟轨道的模拟计算，设计车辆荷载是车轮静载荷的三倍。基于设计参数和无砟轨道客运专线（PDL）的操作条件，中国的统计分析应用了火车和轨道系统耦合动力学。考虑到施工和我国无砟轨道的维护条件，建议恒效列车荷载为1.5倍静载24。温克勒地基支持无砟轨道，与承载板直径对地基系数影响显著。直径越小，基础系数越大1。但当直径D超过76厘米时，直径的变化对地基系数的影响不大。至于无砟轨道，轨道板或支承层的支承面积比较大。因此，为了简单起见，承载板的试算值得直径为76cm，即K76，可用于计算。当变形模量代表亚级压实能力时，可采用层状弹性体力学3对刚性支承板的均匀载荷下亚级表面的位移进行分析，可推导出亚级表面的支承刚度25。每一个无砟轨道的承载层，基础一般比上部结构弱，在列车荷载作用下可以很容易开裂，如果应用了素混凝土或水泥稳定材料。一旦开裂，弯矩是不容易转移到裂纹位置，这导致在整个刚度和弹性模量的减少。因此，减少的弹性模量用于计算26。对于钢筋混凝土结构，加固有利于提高结构层的抗弯刚度。然而，由于可能的裂纹，在裂纹位置的弯曲力矩的传递可能会削弱。因此，只有混凝土的弹性模量是用于计算，而不考虑的加固与裂缝的影响。4.温度应力的计算无碴轨道暴露在空气中。随着外部温度的变化，每一个结构层中的温度会有所不同。一旦由于温度变化无砟轨道的变形受到抑制，结构内就会产生温度应力。对无砟轨道有影响的环境温度变化包括年气温变化和日变化。此外，混凝土的收缩会引起变形，这相当于降低混凝土的温度荷载。以德国的Rheda、Zblin、Bgl为代表的连续式无碴轨道的设计高度重视温度的影响。为了减少在容许范围内的温度裂缝宽度和保持完整的裂缝状态27，据德国无砟轨道设计规范，楼板的配筋率应达到0.8%0.9%。因此，裂缝宽度限制在0.5mm内。动载荷作用下，为保证使用寿命，加固楼板开裂和弯曲应力增量的最小应力的总和必须小于钢筋的疲劳极限，这要求加固的纵向比必须大于1%，以满足裂缝宽度和使用寿命的要求。日本板式轨道设计采用了单元结构，温度变化对轨道板的影响不大。因此，在设计中不考虑温度效应。不过，在测试中发现了轨道板的翘曲位移，此处轨道板是在一个不完全支承的状态。因此，为了解决轨道板由于温度的变化特性，进行着一系列的理论和实验研究4。对于连续板结构，在混凝土收缩和温度降低作用下，混凝土容易产生裂缝，这会导致板内钢筋与混凝土的应力再分配。为了保证安全性和实用性，有必要控制钢筋应力和裂缝宽度。连续板在不同拉伸阶段表现出不同的应力和变形特性。在混凝土裂缝出现之前，通过加固混凝土的变形是协调的。当拉伸混凝土的应力达到其抗拉强度，它会产生裂缝并停止工作，从而导致裂缝附近的粘结破坏。这时，假设不再符合，裂缝处的钢筋承担所有的轴向力。当轴向力增加到钢筋的屈服强度时，混凝土完全断裂并且不能承担张力。所有的轴向力都是由钢筋产生的，所以板的张力极限条件就是钢筋屈服。连续板开裂的轴向力取决于板的抗拉强度和混凝土的截面面积。钢筋的用量对裂缝处的轴向力影响不大，而极限承载力完全取决于屈服强度和钢筋面积。为了避免开裂，应规定连续板的最小配筋率。连续板的开裂经历了两期：不完全开裂和完全开裂。在不完全开裂阶段，随着荷载的增加，裂缝的数量增加，最大裂缝宽度基本保持不变。在完全开裂的阶段，裂纹的数量保持不变，而其宽度随荷载的增加而增加。为了限制裂缝宽度，应控制不完全开裂阶段的裂缝。在不完全开裂的情况下，板内的最大温度力取决于抗拉强度混凝土的截面面积。设计抗拉强度计算的温度力作为一般温度力（主力）。用标
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