路面设计外文翻译---柔性路面设计

1、路面设计外文翻译-柔性路面设计 英文翻译 Flexible pavement design Generally speaking,pavements(and bases) may be divided into two broad classifications or tipes:rigid and flexible. As commonly used in the United States,the term “rigid pavement”is applied to wearing surfaces constructed of Portland-cement concrete. A pa

2、vement constructed of concrete is assumed to possess considerable flexural strength that will permit it to act as a beam and allow it to bridge over minor irregularities which may occor in the base or subgrade on which it rests;hence the term “rigid”.Similarity,a concrete base that supports a brick

3、or block layer might be described as “rigid”. All other types of pavement have traditionally been classed as “flexible”.A commonly used definition is that “a flexible pavement is a structure that maintains contact with and distributes loads to the subgrade and depends on aggregate interlock,particle

4、friction,and cohesion for stability”.Thus,the classical flexible pavement include primarily those pavement that are composed of a series of granular layers topped by a relatively thin high-quality bituminous wearing surface .Typically,the highest-quatily materials are at or near the surface.It shoul

5、d be pointed out that certain pavementsthat have an asphalt surface may behave more like the classical “rigid”pavement,for example, pavement that have very thick asphalt surface or that have base courses composed of aggregate treated with asphalt,cement, or lime-fly ash. However,for convenience of p

6、resentation,these pavements will be considered to be in the flexible class. The structure of flexible pavement is composed of a “wearing surface”, base, subbase(not always used), and subgrade . The wearing surface and the base often comprise two or more layers that are somewhat different in composit

7、ion and that are put down in separate construction operations.On many heavy-duty pavements,asubbase of select material is often placed between the base and subgrade.the wearing surface may range in thickness from less than 1 in. in the case of a bituminous surface used for low-cost, light-traffic lo

8、ads to 6 in. or more of alphalt concrete used for heavily traveled routes. The wearing surface must be capable of withstanding the wear and abrasive effects of moving vehicles and must possess sufficient stability to prevent it from shoving and rutting under traffic loads. In addition,it serves a us

9、eful purpose in preventing the entrance of excessive quantities of surface water into the base subgrade from directly above. The base is a layer (or layers) of very high stability and density. Its principle purpose is to distribute or “spread” the stresses created by wheel loads acting on the wearin

10、g surface so that the stresses transmitted to the subgrade will not be sufficiently great to result in excessive deformation or displacement of that foundation layer. The base must also be of such character that it is not damaged by capillary water and/or frost action. Locally available materials ar

11、e extensively used for base construction, and materials preferred for this type of construction vary wwidely in different sections of the country. For example, the base may be composed of gravel or crushed rock or it may bae a granular material treated with asphalt,cement,or lime-fly ash stabilizing

12、 agents. Asubbase of granular material or stabilized material may be used in areas where frost action is severe, in locations where the subgrade soil is extremely weak. It may also be used , in the interests of economy ,in locations where suitable subbase material are cheap than base materials of hi

13、gher quality. The subgrade is the foundation layer, the structure that must eventually support all the loads which come onto the pavement. In some cases this layer will simply be the natural earth surface. In other or more usual instances it will be compacted soil existing in a cut section or the up

14、per layer of an embankment section. In the fundamental concept of the action of flexible pavement,the combined thickness of subbase (if used), base, and wearing surface must be great enough to reduce the stresses occuring in the subgrade to values that are not sufficiently great to cause excessive d

15、istortion or displacement of the subgrade soil layer. The principle factors entering into the problem of the thickness design of flexible pavement are: (1) Traffic loading. (2) Climate or environment. (3) Material characteristics. A number of other elements must also be considered in order to arrive

16、 at a final thickness design. This include cost, construction, maintenance,an design period. Thus, the students should realize that the design process is complex, and it is highly unlikely that any extremely simple method of approach will prove entirely successful under all conditions. Protection of

17、 the subgrade from the loading imposed by traffic is one of the primariy functions of a pavement structure. The designer must privide a pavement that can withstand a large number of repeated applications of variable-magnitude loading. The magnitude of maximum loading is commonly controlled by legal

18、load limits. Traffic surveys and loadometer studies are often used to establish the relative magnitude and occurrence of the various loading to which a pavement is subjected. Prediction or estimation of the total traffic that will use a pavement during its design ife is a very difficult but obviousl

19、y important task. The climate or environment in which a flexible pavement is to be established has an important influence on the behavior and performance of the various in the pavement and subgrade. Probablly the two climate factors of major significance are temperature and moisture. The magnitude o

20、f temperature and its fluctuations affect the properties of certain materials. For example, high temperatures cause asphaltic concrete to lose stability whereas at low temperatures asphaltic concrete becomes very hard and stiff. Low temperature and temperature fluctuations are also associated with f

21、rost heave and freeze-thaw damage. Granular materials, if not properly graded, can experience frost heave. Likewise, the subgrade can exhibit extensive loss in strength if it becomes frozen. Certain stabilized materials (lime, cement, and lime-fly ash treated) can suffer substantial damage if a larg

22、e number of freeze-thaw cycles occur in the material. Moisture also has an important influence on the behavior and performance of many materials. Moisture is an important ingredient in frost-related damage. Subgrade soils and other paving materials weaken appreciably when saturated, and certain clay

23、ey soil exhibit substantial moisture-included volume change. Subgrade moisture conditions change is affecting road structural strength, stiffness and stability of the important factors. Subgrade moisture influence has the following main factors: atmospheric precipitation and evaporation, infiltratio

24、n of surface water, groundwater impact, temperature changes caused by humidity. Cyclical atmospheric temperature changes throughout the year, day and night temperatures for each day a certain extent cyclical changes. Surface directly exposed to the air, and experiencing the impact of these changes,

25、in particular surface material most affected. Road surface temperature change with the weather temperature is roughly synchronized. Surface layer temperature at different depths within the same generation as the cyclical changes in atmospheric temperature, but the magnitude of change increases with

26、the depth gradually decreased. One of frost damage is frozen, it not only affects the normal running of vehicles, and sometimes the destruction of the pavement structure. Produce frost heave for two reasons: First, as water is frozen, the volume will increase by 9%; second is due to the weak foundat

27、ion soil to freeze the area with water movement results. Subgrade frost heaving caused by three factors: the sensitivity of frozen soil subgrade; temperature decreased slowly; groundwater supply of water to keep the frozen zone. The advent of spring, began to melt the frozen roadbed, will lose their

28、 bearing capacity of soil, leading to road damage, a phenomenon known as the spring melt boil, boil and mainly due to the melting process is top down, when the embankment top soil begins to melt, the water can not be excluded, so the soil has been saturated melting. If by this time a large number of

29、 heavy vehicles, road structure would be seriously damaged. Of the road is a sticky, elastic-plastic materials and the combination of mineral aggregate particles consisting of roads, including the addition of cement concrete as a surface layer and the surface structure of a variety of other grass-ro

30、ots level. Flexible pavement design including pavement layer combination of design, structural calculation and the road pavement material mix design. This chapter elaborates the following aspects: elastic layered system theory, the pavement layer combination of design principles, road design standar

31、ds and parameters, calculation of pavement thickness and the bending stress check. In reality, the road base material and the soil is not in any case have elastic properties. Non-linear elastic - viscous - plastic theory, under certain conditions more accurately describe the stress state of the road

32、, but taking into account the role of the transient driving wheels in the pavement structure, the stress was small, so you can road as each layer is an ideal elastic body, multi-layer linear elastic theory to application to design calculations. Multi-layer linear elastic theory must be used the foll

33、owing basic assumptions: 1.Layers of material are continuous, homogeneous, isotropic and to obey Hookes law, and the displacement and deformation is small; 2. The next level (soil basis) in the horizontal direction and vertical direction down to infinity, The elastic layer is above all have a certai

34、n thickness, but the horizontal direction is infinite; 3. layers of infinite distance in the horizontal direction and the next layer down to infinite depths, the stress, strain and displacement is zero; 4. layers the contact conditions between fully continuous; 5. do not count weight. Flexible Pavem

35、ent Structure Designs mission is to design principles in general under the guidance of the road, according to the road level, requirements and design life of the cumulative equivalent standard axle load axle, considering the supply of road materials, the degree of influence of natural factors and th

36、e specific construction conditions, determine a reasonable level of the pavement structure and select the appropriate economic composition materials, combined into both withstand traffic loads and the role of natural factors, but also give full play to the maximum performance of structural materials

37、, subgrade layer pavement system. Combination of flexible pavement structural design should follow the following basic principles: 1, route, embankment, road do take into consideration the overall design; 2, according to the structure, function and transport layer characteristics of selected structu

38、ral levels; 3, the strength to adapt to traffic load and stiffness combination; 4, pay attention to its own characteristics each layer, make layer combination; 5, the appropriate number of layers and thickness; 6, to consider the impact of water temperature conditions to ensure stability. 柔性路面设计 一般来

39、讲，路面（和路基）可以分为两种类型：刚性路面和柔性路面。“刚性路面”一词在美国通常指由普通水泥混凝土修筑的道路面层。人们认为，混凝土路面可以像梁一样具有较高的弯曲强度并能够跨越基层或路基上的一些微笑的不平整的地带，因此称为“刚性”。同样，支撑砖层或砌体层的混凝土基座也可以说成是刚性的。 所有其他形式的路面在传统上都被归类于柔性路面。柔性路面的一个常用的定义是：柔性路面是与基层紧密接触，并将荷载传递给路基的一种结构，他依靠集料之间的嵌挤力、颗粒的摩擦力和粘结力来保持其稳定性。因此，传统的柔性路面主要是指那些在许多粒料层的上面铺上比较薄的高质量的沥青面层所构成的路面。通常将优质材料用于面层或面层附

40、近。应该指出，某些沥青路面与传统的刚性路面由很大的相似性，例如，铺有较厚沥青面层的路面或由沥青、水泥、石灰/粉煤灰所构成的集料组成的基层的路面。然而，为便于说明，这些路面被认为是柔性的。 柔性路面的结构由面层、基层、底基层（有时不采用）和路基组成。其中面层和基层通常由两层或更多层组成，每一层的材料成分不完全相同并采用分层铺设的施工方法。对于许多承受重载的道路的路面，要选择合适的底基层材料，铺设与基层与路基之间。对于低成本、交通量不大的道路的沥青路面，面层的厚度不应低于1in；对于交通量繁忙的道路，采用沥青混凝土面层，其厚度要达到6in或更厚一些。 面层必须能够承受车辆行驶时所产生的磨蚀作用，并

41、具有足够的稳定性来抵抗车辆荷载作用下的推挤和碾压。除此之外，面层还应该能有效阻止过量的表面积水渗入到其下的面层和路基中去。 路基由一层(或多层)稳定性和密实度很高的材料组成。它的主要作用是将车辆荷载作用于路面时所产生的应力分布或“分散”传递，使得传到路基中的应力不会使其产生过大的变形和位移。基层还必须具有能够抵抗由毛细水或冰冻作用产生的损害的功能。基层的施工材料主要取用于当地，在一个国家的不同地区所使用的材料的种类会有很大的变化。例如，基层可有砾石和碎石构成或者由经过沥青、水泥和石灰/粉煤灰等稳定剂处理过的粒料所构成。 由粒料或稳定材料组成的底基层可以应用于冰冻作用比较严重的和路基土承载力非常

42、差的地区。从经济利益角度出发，它还应用于那些底基层材料比优质的基层材料便宜的地区。 路基是基础层，它必须承受作用在路面上的所有荷载。在某些情况下，路基就是简单的天然土层。在其他或更多情况下，路基则是构成路堑截面或路堤截面上层的压实土层。在柔性路面的基本概念中，底基层（如果有的话）、基层、面层必须具有足够的厚度来减小作用与路基上的应力，避免使路基的土层产生过大的位移和变形。 影响柔性路面设计厚度的主要因素为： （1） 交通荷载。 （2） 气候或环境。 （3） 材料特性。 为了获得最终的厚度设计结果，还必须考虑一些其他因素，包括造价、施工、维修保养和设计期限。因此，学生们应该认识到设计过成是很复杂的，不可能由任何一种非常简单的方法来成功解决处于不同条件下的所有问题。 保护路基使其免受由交通运输量所产生的荷载的损伤是路面结构层的一项主要功能。设计者还必须使所