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1、Lesson 27,HIGHWAY ENGINEERING公路工程,Transportation has always been one of the most important aspects of civil engineering.One of the greatest accomplishments of Roman engineers was the high way system that made rapid communication possible between Rome and the provinces of the empire.Modern highways a
2、re built according to the principles laid down in the eighteenth and early nineteenth centuries.Generally speaking,alignment,subgrade,and pavement are the most basic three parts of the modern highways.,交通一直是土木工程中最重要的方面之一。一位罗马工程师的最伟大的成就是公路体系，其使快速通讯成为可能。现代公路的修建是根据十八和十九世纪初所定下的原则。一般而言，线性，路基，路面是现代公路的最基本的
3、三个部分。,Introduction,accomplishment成就alignment线性subgrade路基pavemen路面,The alignment of a road includes horizontal alignment and vertical alignment.The horizontal alignment of a road is shown on the plan view and is a series of straight lines called tangents connected by circular curves.In modern practic
4、e it is common to interpose transition or spiral curves between tangents and circular curves.So the elements of the horizontal alignment are tangent,circular curve,and transition curve,as shown in following Fig.27-1.,公路线形包括平面线形和纵断面线形。道路的平面线形显示在平面图和一系列的直线称为圆曲线连接切线。目前在实际操作中，一般在切线和圆曲线之间插入缓和曲线或螺旋曲线。平面线形
5、的组成是切线（直），圆曲线和过渡曲线，如图中下面的图27-1。,1.Alignment（线形）,horizontal alignment平面线形vertical alignment纵断面线形tangent切线circular curve圆曲线,Curve line,Straight line,The vertical alignment of a road is shown on the cutaway view.The elements of the vertical alignment are tangents,vertical curves.Usually there are two t
6、ype of vertical curve:convex vertical curve and concave vertical curve,as shown in following Fig.27-2.,道路的纵断面线形显示在剖视图。纵断面线形的组成是切线，竖曲线。通常有两种类型的竖曲线：垂直凸竖曲线和凹竖曲线，如图以下所示27-2。,cutaway 剖面convex 凸的concave 凹的,Alignment must be consistent.Sudden changes from flat to sharp curves and long tangents followed by
7、sharp curves must be avoided;otherwise,accident hazards will be created.Likewise,placing circular curves of different radii end to end(compound curves)or having a short tangent between two curves is poor practice unless suitable transitions between them are provided.,线形必须一致（平面线形和纵断面线形）。必须避免平地突然变化为急弯
8、以及很长的切线后紧跟着锐曲线，否则就会产生事故风险。同样地把不同半径的圆曲线尾尾相连、或两条曲线之间插入短切线是不良做法，除非曲线之间有适当的缓和曲线。,consistent一致likewise同样地radii半径,Long,flat curves are preferable at all times,as they are pleasing in appearance and decrease possibility of future obsolescence.Long,flat curves should be used for small changes in direction,a
9、s short curves appear as kink.Also horizontal and vertical alignment must be considered together,not separately.For example,a sharp horizontal curve beginning near a crest can create a serious accident hazard.,在任何时候都长且平坦的曲线都是优选，因为它们在外观上令人愉悦并能减少将来报废的可能性。长，平面曲线应该用于在方向上的微小变化，如短的曲线显示为“扭结”。同时平面线形和纵断面线形必须
10、一起考虑，而不是分开。例如，一个锐的平曲线的开始接近高峰时可能会产生严重事故的危险。,obsolescence报废crest高峰,A vehicle traveling in a curved path is subject to centrifugal force.This is balanced by an equal and opposite force developed through superelevation and side friction.From a highway design standpoint,both superelevation and side frict
11、ion cannot exceed certain maximums,and these controls place limits on the sharpness of curves that can be used with a design speed.,车辆在弯曲道路行驶受到离心力。这个平衡通过大小相等方向相反的超高和侧向摩擦力来达到。从公路设计的观点来讲，超高和侧向摩擦力都不能超过某个最大值，这些控制值设置了曲线锐度限值，曲线锐度限值可以与设计速度建立联系。,vehicle 车辆centrifugal force离心力superelevation超高side friction侧向摩
12、擦力,When roads intersect or a railroad spans across a road,the road intersections are needed.The intersection can be at-grade intersection and grade-separated junction.The freeways only adopt the latter intersection.The typical at-grade crossings are cross roads,T intersection,and rotary intersection
13、,as shown in following Fig.27-3.,当相交的道路或铁路横跨道路时，需要设置道路交叉口。交叉口可以是平面交叉的和立体交叉。该高速公路仅采用后者的交叉口。典型的平面交叉口的十字路口，T形交叉，及环形交叉，如图下所示 27-3。,intersect 交叉junction 连接rotary 环形,Clover-leaf Interchange,Diamond Interchange,Grade-separated junctions,Rotary Interchange,Trumpet Interchange,苜蓿叶 菱形 环形 喇叭形,立体交叉口,高速公路,普通公路与高
14、速公路的转弯线形的比较,When roads intersect or a railroad spans across a road,the road intersections are needed.The intersection can be at-grade intersection and grade-separated junction.The freeways only adopt the latter intersection.The typical at-grade crossings are cross roads,T intersection,and rotary int
15、ersection,as shown in following Fig.27-3.,当相交的道路或铁路横跨道路时，需要设置道路交叉口。交叉口可以是平面交叉的和立体交叉。该高速公路仅采用后者的交叉口。典型的平面交叉口的十字路口，T形交叉，及环形交叉，如图下所示 27-3。,intersect 交叉junction 连接rotary 环形,The foundations under pavement of highways are subgrade,so highway subgrade(or basement soil)may be defined as the supporting struc
16、ture on which pavement and its special under courses rest.The purpose of a pavement is to provide a smooth surface over which vehicles may pass under all climate conditions.Because natural terrains are uneven,to get smooth road,cutting and filling are needed to change the natural terrain.Subgrades a
17、re classified into embankment,cutting,and part-cut part-fill subgrade,。,作业：将下段英文翻译成汉语。,在公路路面以下的基础是路基，所以路基（或基层土壤）可被定义为支撑路面及其特殊下层的结构。路面的作用是提供一个任何气候条件下车辆都可能通过的平滑的表面。由于天然地形凹凸不平，为了让道路平顺，挖方和填方都需要改变自然地形。路基被分类成 路堤，路堑，半挖半填路基。,In cut sections,the subgrade is the original soil lying below the special layers de
18、signated as base and subbase material.In fill sections,the subgrade is constructed over the native ground and consists of imported material from nearby roadway cuts or from borrow pits.,在挖方部分，路基是置于被设计为基座和底基层特殊层下方的天然土。在填方部分，路基建造于原土之上并由附近公路挖方或从取土坑中的土这类外来材料组成。,The performance of the pavement is affecte
19、d by the characteristics of the subgrade.Desirable properties that the subgrade should possess include strength,drainage,ease of compaction,permanency of compaction,and permanency of strength.,在路面的性能受路基特性的影响。路基的理想性能，应具有包括强度，排水，易压实性，压实的永久性和强度的永久性。,drainage排水possess 控制，具有,Soils engineers agree that th
20、e properties of a soil mixture are influenced more by moisture than by any other cause.Soils that have ample strength and supporting power under one set of moisture conditions may be entirely unsatisfacory if the percentage of moisture changes.One difficulty with soils in highway subgrades is that t
21、hey are subject to such moisture changes.,土力学工程师赞同湿度对土壤混合物性能的影响比其他因素大。在一个湿度条件下有足够强度与支撑能力的土体，如果湿度的百分比发生变化，土体可能完全不能令人满意。土体在公路路基中的一个困难是承受着湿度的变化。,mixture混合物moisture湿度percentage 百分比,One difficulty with soils in highway subgrades is that they are subject to such moisture changes.That is the reason why dra
22、inage is an important consideration of subgrades.Since subgrade vary considerably,it is necessary to make a through study of the soils in place.,土体在公路路基中的一个困难是承受着湿度的变化。这也是在路基中为什么需重点考虑排水的原因。由于路基的变化相当大，很有必要采取一种方法研究做土壤取代物的研究。,subject to受.in place 替代,Soil is a highly variable material;the interrelations
23、hip of soil texture,density,moisture content,and strength are complex,and behavior under repeated loads is difficult to evaluate.Because of the complexity of the problem,it is not possible to set down rules that will be suitable for all case.,土壤是高度多变的材料；土壤的结构、密度、含水率及强度的内在关系是非常复杂的，在荷载重复作用下的状态是很难估计的。由
24、于问题的复杂性，不可能制定适用于所有状况的规则.,interrelationship内在关系texture结构density密度evaluate估计,For example,the supporting power of soils increases with density.A road constructed on a given soil may be entirely satisfactory if the soil is properly compacted.On the other hand,the road may fail if the soil is insufficien
25、tly compacted,particularly if the voids become filled with water.,例如，随着密度的提高，土壤的支撑力增强。路修建在被适当压实的给定土体上那会是完全令人满意的。另一方面，如果土没有被充分压缩，特别是如果土体的孔隙充满了水，道路可能会失效。,Translate the following sentences into Chinese.,highway alignment,Exercises,clover-leaf interchange,centrifugal force,cutaway view,moisture,transiti
26、on curve,plan view,4.苜蓿叶立体交叉,5.缓和曲线,8.离心力,2.公路线形,6.平面图,3.路基,1.湿度,subgrade,7.剖面图,1.路面2.平面交叉3.急弯，锐曲线4.设计速度5.路堑,Translate the following words into English.,pavement,at-grade intersection,Sharp curves,design speed,cutting,1.In modern practice it is common to interpose transition or spiral curves between
27、 tangents and circular curves.,2.必须避免平地突然变化为急弯以及很长的切线后紧跟着锐曲线，否则就会产生事故风险。,2.Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided;otherwise,accident hazards will be created.,1.目前在实际操作中，一般在切线和圆曲线之间插入缓和曲线和螺旋曲线。,3.因为自然地形是不平坦的，为了得到平坦的道路，需要挖方和填方来改变自然地形。,3.Beca
28、use natural terrains are uneven,to get smooth road,cutting and filling are needed to change the natural terrain.,4.Soils that have ample strength and supporting power under one set of moisture conditions may be entirely unsatisfacory if the percentage of moisture changes.,5.另一方面，如果土没有被充分压缩，特别是如果土体的孔
29、隙充满了水，道路可能会失效。,5.On the other hand,the road may fail if the soil is insufficiently compacted,particularly if the voids become filled with water.,4.在一个湿度条件下有足够强度与支撑能力的土体，如果湿度的百分比发生变化，土体可能完全不能令人满意。,2.In cut sections,the subgrade is the original soil lying below the special layers designated as base an
30、d subbase material.,2.在挖方部分，路基是置于被设计为基座和底基层特殊层下方的天然土。,1.The horizontal alignment of a road is shown on the plan view and is a series of straight lines called tangents connected by circular curves.,1.道路的平面线形显示在平面图上以及一系列的直线称之为连接圆曲线的切线。,3.For example,a sharp horizontal curve beginning near a crest can
31、create a serious accident hazard.,3.例如，一个锐的平曲线的开始接近高峰时可能会产生严重事故的危险。,4.Desirable properties that the subgrade should possess include strength,drainage,ease of compaction,permanency of compaction,and permanency of strength.,4.路基的理想性能，应具有包括强度，排水，易压实，压实的永久性和强度的永久性。,5.Soil is a highly variable material;t
32、he interrelationship of soil texture,density,moisture content,and strength are complex,and behavior under repeated loads is difficult to evaluate.,5.土壤是高度多变的材料；土壤的结构、密度、湿度含量及强度的内在关系是非常复杂的，在荷载重复作用下的状态是很难估计的。,Answer the following questions briefly.1.What are the main parts of the modern highways?Gener
33、ally speaking,alignment,subgrade,and pavement are the most basic three parts of the modern highways.2.Please list the elements of horizontal alignment and vertical alignments of highway.The elements of the horizontal alignment are tangent,circular curve,and transition curve,the elements of the verti
34、cal alignment are tangents,vertical curves.3.For the freeway,which road intersection can be adopted?The freeways adopt the grade-separated junction.4.Why the drainage is an important consideration of highway subgrade?One difficulty with soils in highway subgrades is that they are subject to such moisture changes.,Thats all,thank you.,
