外文翻译--公路和机场路面设计

1、中文2942字本科生毕业设计（论文）外文资料翻译翻译资料名称（外文）： Highway and Airport Pavement Design 翻译资料名称（中文）： 公路和机场路面设计 学 院： 建筑工程学院 系 土木工程 专 业： 土 木 工 程 （道桥） 班 级： 学 号： 姓 名： 指导教师： 完成日期： 2021 年 02 月 20 日14Highway and Airport Pavement Design（Excerpt）T. F. Fwa National University of Singapore1. Introduction Pavements are designed

2、 and constructed to provide durable all-weather traveling surfaces for safe and speedy movement of people and goods with an acceptable level of comfort to users. These functional requirements of pavements are achieved through careful considerations in the following aspects during the design and cons

3、truction phases: (a) selection of pavement type, (b) selection of materials to be used for various pavement layers and treatment of subgrade soils, (c) structural thickness design for pavement layers, (d) subsurface drainage design for the pavement system, (e) surface drainage and geometric design,

4、and (f ) ridability of pavement surface.The two major considerations in the structural design of highway and airport pavements are material design and thickness design. Material design deals with the selection of suitable materials for various pavement layers and mix design of bituminous materials (

5、for flexible pavement) or portland cement concrete (for rigid and interlocking block pavements). These topics are discussed in other chapters of this handbook. This chapter presents the concepts and methods of pavement thickness design. As the name implies, thickness design refers to the procedure o

6、f determining the required thickness for each pavement layer to provide a structurally sound pavement structure with satisfactory performance for the design traffic over the selected design life. Drainage design examines the entire pavement structure with respect to its drainage requirements and inc

7、orporates facilities to satisfy those requirements.2Pavement Types and Materials2.1 Flexible versus Rigid PavementTraditionally, pavements are classified into two categories, namely flexible and rigid pavements. The basis for classification is the way by which traffic loads are transmitted to the su

8、bgrade soil through the pavement structure. As shown in Fig. 2.1, a flexible pavement provides sufficient thickness for load distribution through a multilayer structure so that the stresses and strains in the subgrade soil layers are within the required limits. It is expected that the strength of su

9、bgrade soil would have a direct bearing on the total thickness of the flexible pavement. The layered pavement structure is designed to take advantage of the decreasing magnitude of stresses with depth. A rigid pavement, by virtue of its rigidity, is able to effect a slab action to spread the wheel l

10、oad over the entire slab area, as illustrated in Fig. 2.1. The structural capacity of the rigid pavement is largely provided by the slab itself. For the common range of subgrade soil strength, the required rigidity for a portland cement concrete slab (the most common form of rigid pavement construct

11、ion) can be achieved without much variation in slab thickness. The effect of subgrade soil properties on the thickness of rigid pavement is therefore much less important than in the case of flexible pavement. FIGURE 2.1 Flexible and rigid pavements.2.2 Layered Structure of Flexible Pavement2.2.1 Sur

12、face CourseIn a typical conventional flexible pavement, known as asphalt pavement, the surface course usually consists of two bituminous layers a wearing course and a binder course. To provide a durable, watertight, smooth-riding, and skid-resistant traveled surface, the wearing course is often cons

13、tructed of dense-graded hot mix asphalt with polish-resistant aggregate. The binder course generally has larger aggregates and less asphalt. The composition of the bituminous mixtures and the nominal top size aggregates for the two courses are determined by the intended use, desired surface texture

14、(for the case of wearing course), and layer thickness. A light application of tack coat of water-diluted asphalt emulsion may be used to enhance bonding between the two courses. Table 2.1 shows selected mix compositions listed in ASTM Standard Specification D3515 1992. Open-graded wearing courses, s

15、ome with air void exceeding 20%, have also been used to improve skid resistance and reduce splash during heavy rainfall by acting as a surface drainage layer. 2.2.2 Base CourseBase and subbase layers of the flexible pavement make up a large proportion of the total pavement thickness needed to distri

16、bute the stresses imposed by traffic loading. Usually base course also serves as a drainage layer and provides protection against frost action. Crushed stone is the traditional material used for base construction to form what is commonly known as the macadam base course. In this construction, chokin

17、g materials consisting of natural sand or the fine product resulting from crushing coarse aggregates are added to produce a denser structure with higher shearing resistance. Such base courses are called by different names, depending on the construction method adopted. Dry-bound macadam is compacted

18、by means of rolling and vibration that work the choking materials into the voids of larger stones. For water-bound macadam, after spreading of the choking materials, water is applied before the entire mass is rolled. Alternatively, a wet-mix macadam may be used by premixing crushed stone or slag wit

19、h a controlled amount of water. The material is spread by a paving machine and compacted by a vibrating roller. Granular base materials may be treated with either asphalt or cement to enhance load distribution capability. Bituminous binder can be introduced by spraying heated asphalt cement on conso

20、lidated and rolled crushed stone layer to form a penetration macadam road base. Alternatively, bituminous road bases can be designed and laid as in the case for bituminous surface courses. Cement-bound granular base material is plant mixed with an optimal moisture content for compaction. It is laid

21、by paver and requires time for curing. Lean concrete base has also been used successfully under flexible pavements. TABLE 2.1 Example Composition of Dense Bituminous Paving Mixtures2.2.3 Subbase CourseThe subbase material is of lower quality than the base material in terms of strength, plasticity, a

22、nd gradation, but it is superior to the subgrade material in these properties. It may be compacted granular material or stabilized soil, thus allowing building up of sufficient thickness for the pavement structure at relatively low cost. On a weak subgrade, it also serves as a useful working platfor

23、m for constructing the base course. subbase course may be omitted if the subgrade soil satisfies the requirements specified for subbase material.2.2.4 Prepared SubgradeMost natural soils forming the roadbed for pavement construction require some form of preparation or treatment. The top layer of a s

24、pecified depth is usually compacted to achieve a desired density. The depth of compaction and the compacted density required depend on the type of soil and magnitudes of wheel loads and tire pressures. For highway construction, compaction to 100% modified AASHTO density covering a thickness of 12 in

25、. (300 mm) below the formation level is commonly done. Compaction depth of up to 24 in. (600 mm) may be required for heavily trafficked pavements. For example, in the case of cohesive subgrade, the Asphalt Institute 1991 requires a minimum of 95% of AASHTO T180 (Method D) density for the top 12 in.

26、(300 mm) and a minimum of 90% for all fill areas below the top 12 in. (300 mm). For cohesionless subgrade, the corresponding compaction requirements are 100 and 95%, respectively.Due to the higher wheel loads and tire pressures of aircraft, many stringent compaction requirements are found in airport

27、 pavement construction.In some instances it may be economical to treat or stabilize poor subgrade materials and reduce the total required pavement thickness. Portland cement, lime, and bitumen have all been used successfully for this purpose. The choice of the method of stabilization depends on the

28、soil properties, improvement expected, and cost of construction.2.3 Rigid PavementRigid pavements constructed of portland cement concrete are mostly found in heavy-traffic highways and airport pavements. To allow for expansion, contraction, warping, or breaks in construction of the concrete slabs, j

29、oints are provided in concrete pavements. The joint spacing, which determines the length of individual slab panels, depends on the use of steel reinforcements in the slab. The jointed plain concrete pavemen (JPCP), requiring no steel reinforcements and thus the least expensive to construct, is a pop

30、ular form of construction. Depending on the thickness of the slab, typical joint spacings for plain concrete pavements are between 10 and 20 ft (3 and 6 m). For slabs with joint spacing greater than 6 m, steel reinforcements have to be provided for crack control, giving rise to the use of jointed re

31、inforced concrete pavements (JRCP) and continuously reinforced concrete pavements (CRCP). Continuously reinforced concrete pavements usually contain higher than 0.6% steel reinforcement to eliminate the need to provide joints other than construction and expansion joints. The base course for rigid pa

32、vement, sometimes called subbase, is often provided to prevent pumping (ejection of foundation material through cracks or joints resulting from vertical movement of slabs under traffic). The base course material must provide good drainage and be resistant to the erosive action of water. When dowel b

33、ars are not provided in short jointed pavements, it is common practice to construct cement-treated base to assist in load transfer across the joints.3Considerations for Highway and Airport PavementsThe two pavement types, flexible and rigid pavement, have been used for road and airport pavement cons

34、truction. The choice of pavement type depends on the intended functional use of the pavement (such as operating speed and safety requirements), types of traffic loading, cost of construction, and maintenance consideration.The main differences in design considerations for highway and airport pavement

35、s arise from the characteristics of traffic using them. Over the typical design life span of 10 to 20 years for flexible pavements, or 20 to 40 years for rigid pavements, a highway pavement will be receiving highly channelized wheel load applications in the millions. Consideration of the effects of

36、load repetitions such as cumulative permanent deformation, crack propagation, and fatigue failure becomes important. The total number of load applications in the entire design life of a highway pavement must therefore be known for pavement structural design. In contrast, the frequency of aircraft lo

37、ading on airport pavement is much less. There are also the so-called wander effect of aircraft landing and taking off and the large variation in the wheel assembly configurations and layout of different aircraft. These make wheel loading on airport pavements less channelized than on highway pavement

38、s. Identification of the most critical aircraft is therefore necessary for structural design of airport pavements. Another important difference is in the magnitude of wheel loads. Airport pavements receive loads far exceeding those applied on the highway. An airport pavement may have to be designed

39、to withstand equivalent single wheel loads of the order of 50 t (approximately 50 tons), whereas the maximum single wheel load allowed on the road pavement by most highway authorities is about 10 t (approximately 10 tons). Furthermore, the wheel tire pressure of an aircraft of about 1200 kPa (175 ps

40、i) is nearly twice the value of a normal truck tire. These differences greatly influence the material requirements for the pavements.公路和机场路面设计（节选）T. F. Fwa新加坡国立大学1.绪论路面的设计和建造是为了能够给行人和货物在其上面进行全天候持久的安全迅速活动提供一个舒适合意的水平环境。路面的这些功能要求可以通过在设计和施工过程中仔细考虑如下几个方面来实现：（a）合理选择路面类型；（b）合理选择各路面层材料和路基土处理；（c）合理进行各路面层厚度划分

41、；（d）地下排水系统设计；（e）路面排水系统和几何尺寸设计；（f）路面的抵抗能力。公路和机场路面在结构设计上的两个主要考虑因素是材料设计和厚度设计。材料设计要合理选择各路面层材料，满足沥青混合料（柔性路面）或者水泥混凝土（刚性路面）配合比设计要求。这些问题将在本手册的其他章节中进行讨论。本章介绍路面厚度设计的概念和方法。顾名思义，厚度设计是指确定每个路面层的厚度，形成一个稳定的路面结构，使得在规定的设计年限内满足设计交通量的要求。排水系统设计可检验整个路面结构在它的排水要求和一体化设施方面是否满足相关要求。2. 路面类型和材料2.1柔性路面和刚性路面传统上，根据通过路面结构传递到路基土上的交通

42、荷载，路面分为两类，即柔性路面和刚性路面。如图2.1所示，柔性路面具有足够的厚度来承受多层结构传递的分布荷载，使得路基土层的应力应变值控制在容许范围内。柔性路面地基土的强度将直接关系到总厚度。路面结构层的设计充分利用到了应力随着土层的加深而减少这一原理。刚性路面依靠其刚度，能够有效传递作用在整块混凝土板块上的车辆荷载，如图2.1所示。刚性路面的结构承载力大部分都是由混凝土板块自身提供。在地基土强度的一般变化范围内，硅酸盐水泥混凝土面板（最常见的刚性路面结构）的刚度要求无需板块厚度发生多大变化就能满足。因此，路基土性能对刚性路面厚度的影响要比柔性路面小得多。图2.1 柔性和刚性路面2.2 柔性路

43、面结构层次2.2.1 面层沥青路面是一种典型的传统柔性路面，它的面层通常由两个沥青层组成，即磨耗层和联结层。为了保证路面的耐久性、不透水、平稳行车和防滑，磨耗层一般由热拌沥青混凝土和耐磨碎石组成，而联结层则一般由大量的碎石和少量的沥青组成。这两层的沥青混合料的组成以及骨料的最大公称直径是由使用目的、所希望的表面结构（针对磨耗层而言）、层厚来决定的。由水稀释乳化沥青组成的粘结层的一个简易运用就是增强磨耗层和联结层之间的粘结性。表2.1显示了列在ASTM标准规格D35151992 上的经选定的混合成分。有些空隙率超过20%的开级配磨耗层也可作为强降雨天气时的地面排水层，用于提高抗滑性和防止溅水。2

44、.2.2 基层柔性路面的基层和底基层占总路面厚度的大部分，它们用来分配交通荷载所产生的应力。通常基层也可作为排水层，并提供保护免受霜冻作用。碎石是基层施工的常用材料，构成俗称的碎石基层。在本阶段施工过程中，填充材料选用天然砂或者良好级配的压碎碎石集料，形成具有更高抗剪承载力的密实结构。根据施工方法的不同，这样的基层有不同名称。表2.1 浓沥青摊铺混合料组成示例干结碎石通过轧制和振动，使填充料填塞到大块石头间的空隙，达到压实的目的。而对于水结碎石，在填充材料填塞空隙后，水在整块被轧制前就得到应用。另外，通过用适量的水预拌碎石或矿渣，湿混碎石也可被使用。这些材料先用摊铺机摊铺，然后再用振动压路机压

45、实。颗粒基层材料可选用沥青或者水泥以提高荷载分配能力。为建造渗透碎石路面基层，在固结并压实的碎石层上面喷洒热拌沥青混凝土时可采用沥青结合料。沥青路面基层的设计和摊铺可以作为沥青面层的示例。水泥稳定基层粒料在达到压实时的最佳含水量后采用厂拌法，通过摊铺机摊铺，养护足够的时间。贫混凝土基层也被成功运用到柔性路面。2.2.3 底基层跟基层材料相比，底基层材料的强度、塑性和级配要求都要更低，但是在这些性能上，底基层更具优势。可能因为采用了压实粒料或稳定土，路面结构造价相对较低，但厚度却足以满足要求。对于柔弱底基层，它也可以作为构建基层的有用的施工平台。如果路基土满足底基层材料的特定要求，也可以不构建底

46、基层。2.2.4 素土夯实层用于路面建筑的绝大部分天然土路床要求进行素土夯实或者特殊处理。某一指定深度的顶层通常需要压实来获得理想的压实密度。压实深度和压实密度的要求要根据土壤类型、车轮荷载大小以及轮胎压力而定。在公路建筑上，压实至100%修改过的 AASHTO（美国国家公路与运输协会标准）密度时，覆盖厚度为12英寸 (300毫米)，通常的做法都是低于这个正常水平的。对于重交通路面，压实深度可能要求高达24英寸（600毫米）。例如，对于粘性路基，沥青研究所（1991）要求达到最低的95%AASHTO标准 T180次 (D法)密度时，厚度为顶级12英寸（300毫米），在所有填方中最少90%要低于

47、顶级12英寸（300毫米）。对于无粘性路基，相应的压实要求是100%和95%。由于飞机的轮载和轮压更大，因此在机场路面施工时，对压实要求更为严格。在某些情况下，处理或者加固软弱不良路基材料是一种经济的做法，并且可以减少所需的总路面厚度。硅酸盐水泥、石灰、沥青等的成功运用就是为了达到这样的效果。选择怎样的加固方法要根据土壤性质、预期改善效果和建设成本而定。2.3 刚性路面在交通繁忙的公路和机场路面，硅酸盐水泥混凝土刚性路面结构几乎随处可见。考虑到混凝土板的膨胀、收缩、翘曲或者开裂，混凝土路面设有接缝。接缝间距取决于混凝土板中钢筋的选用，它能决定单独每板块的长度。接缝式素混凝土路面结构（JPCP）

48、是一种很流行的建筑形式，它不需要钢筋，因而造价最低。根据混凝土板厚度的大小，普通混凝土路面的标准接缝间距是1020英尺（36米）。当混凝土板块接缝间距大于6米时，需要增设钢筋防止开裂，从而进入到使用接缝式钢筋混凝土路面（JRCP）和连续钢筋混凝土路面（CRCP）阶段。连续钢筋混凝土路面通常多含0.6%的钢筋，用来减少除结构和伸缩缝以外的接缝数量。刚性路面基层，有时又叫做底基层，通常用于防止出现唧泥（在交通作用下，混凝土板垂直运动，基础材料通过裂缝或者接缝喷出的现象）。基层材料必须具有良好的排水性能并且能够抵抗水的腐蚀作用。当短缝路面没有传力杆时，通常的做法是构建水泥稳定基层来协助传递横穿接缝的

49、荷载。3. 公路和机场路面注意事项柔性路面和刚性路面这两种路面类型已经广泛运用到了公路和机场路面建筑。选择哪种路面类型要根据路面的预期使用功能（例如运行速度和安全要求）、交通荷载类型、工程造价和维修代价而定。公路和机场路面设计考虑因素方面主要的不同在于使用它们的交通特点各异。柔性路面的标准设计年限是10-20年，刚性路面是20-40年，在它们各自的设计年限内，公路路面将受到数于百万计的高渠化轮载作用。考虑到重复荷载的影响例如累积永久变形、裂纹扩展和疲劳破坏变得重要，路面结构设计必须考虑到整个设计年限范围内的荷载作用总效应。相比之下，机场路面的负荷频率要小得多。所谓的飞机着陆、起飞漂移，大差异的

50、机轮装配配置，不同飞机的布局设计，这些因素使得作用在机场路面的轮载渠化程度比公路路面低。因此在机场路面的结构设计中，以最关键的飞机为标准是很有必要的。另外一个重要的不同就在于轮载的大小。机场路面受到的荷载远大于作用在公路上的。机场路面要设计能够承受50吨（或接近50吨）的等效单轮荷载，然而大部分公路部门所允许的最大公路路面单轮荷载只有10吨（或接近10吨）。此外，一架飞机的轮胎压力大约是1200KP（175磅），接近于两倍的标准卡车轮胎压力。这些不同因素对路面材料的要求影响都很大。 教师见习报告总结期待已久的见习已经结束了，在龙岩三中高中部见习听课，虽然只是短短的两个星期，但感触还是蛮深的，以

51、前作为一名学生坐在课室听课，和现在作为一名准教师坐在课室听课是完全不同的感受，感觉自己学到了一些在平时课堂上学不到的东西。在这里，我获得的不仅是经验上的收获，更多是教学管理，课堂教学等的理念，以及他们带给我的种种思考。教育见习实践过程：听课。教育见习的主要目的是让学生在指导教师的引导下，观摩教师上课方法、技巧等。听课是教育见习的主要内容。我院规定在一周的见习中需完成至少6课的见习任务。我在教师的安排指导下，分别对高一、高二物理专业课型为主，其他课型齐头的方式，积极主动的完成了听课任务，收到良好的效果。我听的第一节课是高二（8）班，这是一个平衡班，水平不如实验班高。在上课前。科任老师已经跟我说了这个班的纪律是比较差的，而且成绩也不是很好。在我听课期间，确实有几个学生在课堂上说话，但是我发现了一个有趣的现象，这个现象我在往后的几个班都发现了，就是绝大部分的学生的学习热情都好高涨，积极举手发言，积极参与课堂活动。我跟老师们提起这个现象的时候，科任老师就跟我说，一个班里不可能所有的学生都能全神贯注地听完一节课，所以作为一名教师，应该想办法吸引学生的注意力，调动的积极性，比如可以以