道路與橋梁專業(yè)外文翻譯--公路幾何設(shè)計(jì)

1、<p><b>　　中文3463字</b></p><p>　　本科畢業(yè)設(shè)計(jì)（論文）</p><p>　　二○一二年五月十八日</p><p>　專業(yè)名稱：土木工程專業(yè)（道路與橋梁）</p><p>　年級班級：道橋08-5班</p><p>　學(xué)生姓名：</p><

2、p>　指導(dǎo)教師：</p><p>　　Geometric Design of Highways</p><p>　　The road is one kind of linear construction used for travel. It is made of the roadbed, the road surface, the bridge, the culvert and t

3、he tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility.</p><p>　　The roadbed is the base of road surface, road shoulder, side slo

4、pe, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the base of travel, must guarantee that it has the enough intensity and the stability

5、 that can prevent the water and other natural disaster from corroding.</p><p>　　The road surface is the surface of road. It is single or complex structure built with mixture. The road surface require being s

6、mooth, having enough intensity, good stability and anti-slippery function. The quality of road surface directly affects the safe, comfort and the traffic.</p><p>　　Highway geometry designs to consider Highwa

7、y Horizontal Alignment, Vertical Alignment two kinds of linear and cross-sectional composition of coordination, but also pay attention to the smooth flow of the line of sight, etc. Determine the road geometry, consider t

8、he topography, surface features, rational use of land and environmental protection factors, to make full use of the highway geometric components of reasonable size and the linear combination.</p><p>　　1.Alig

9、nment Design</p><p>　　The alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circular. In modern practice it is common to interpose transition or sp

10、iral curves between tangents and circular curves.</p><p>　　Alignment must be consistent. Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided; otherwise, accide

11、nt 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 pro

12、vided. Long, flat curves are preferable at all times, as they are pleasing in appearance and decrease possibility of future obsolesc</p><p>　　A vehicle traveling in a curved path is subject to centrifugal fo

13、rce. This is balanced by an equal and opposite force developed through cannot exceed certain maximums, and these controls place limits on the sharpness of curves that can be used with a design speed. Usually the sharpnes

14、s of a given circular curve is indicated by its radius. However, for alignment design, sharpness is commonly expressed in terms of degree of curve, which is the central angle subtended by a 100-ft length of curve. D</

15、p><p>　　Tangent sections of highways carry normal cross slope; curved sections are super elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center l

16、ine of each individual roadway at profile grade while raising the outer edge and lowering the inner edge to produce the desired super elevation is attained some distance beyond the point of curve. </p><p>　　

17、If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp circular curve, riding is extremely uncomfortable. As the car approaches a curve, super elevation begins and the ve

18、hicle is tilted inward, but the passenger must remain vertical since there is on centrifugal force requiring compensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider

19、outward from his vertical position. To achieve a position of</p><p>　　Easement curves have been used by the railroads for many years, but their adoption by highway agencies has come only recently. This is un

20、derstandable. Railroad trains must follow the precise alignment of the tracks, and the discomfort described here can be avoided only by adopting easement curves. On the other hand, the motor-vehicle operator is free to a

21、lter his lateral position on the road and can provide his own easement curves by steering into circular curves gradually. However, this weaving</p><p>　　For the same radius circular curve, the addition of ea

22、sement curves at the ends changes the location of the curve with relation to its tangents; hence the decision regarding their use should be made before the final location survey. They point of beginning of an ordinary ci

23、rcular curve is usually labeled the PC (point of curve) or BC (beginning of curve). Its end is marked the PT (point of tangent) or EC (end of curve). For curves that include easements, the common notation is, as stationi

24、ng inc</p><p>　　On two-lane pavements provision of a wilder roadway is advisable on sharp curves. This will allow for such factors as (1) the tendency for drivers to shy away from the pavement edge, (2) incr

25、eased effective transverse vehicle width because the front and rear wheels do not track, and (3) added width because of the slanted position of the front of the vehicle to the roadway centerline. For 24-ft roadways, the

26、added width is so small that it can be neglected. Only for 30mph design speeds and curves</p><p><b>　　2. Grades</b></p><p>　　The vertical alignment of the roadway and its effect on t

27、he safe and economical operation of the motor vehicle constitute one of the most important features of road design. The vertical alignment, which consists of a series of straight lines connected by vertical parabolic or

28、circular curves, is known as the “grade line.” When the grade line is increasing from the horizontal it is known as a “plus grade,” and when it is decreasing from the horizontal it is known as a “minus grade.” In analyzi

29、ng </p><p>　　In the establishment of a grade, an ideal situation is one in which the cut is balanced against the fill without a great deal of borrow or an excess of cut to be wasted. All hauls should be down

30、hill if possible and not too long. The grade should follow the general terrain and rise and fall in the direction of the existing drainage. In mountainous country the grade may be set to balance excavation against embank

31、ment as a clue toward least overall cost. In flat or prairie country it will be approx</p><p>　　Changes of grade from plus to minus should be placed in cuts, and changes from a minus grade to a plus grade sh

32、ould be placed in fills. This will generally give a good design, and many times it will avoid the appearance of building hills and producing depressions contrary to the general existing contours of the land. Other consid

33、erations for determining the grade line may be of more importance than the balancing of cuts and fills.</p><p>　　Urban projects usually require a more detailed study of the controls and finer adjustment of e

34、levations than do rural projects. It is often best to adjust the grade to meet existing conditions because of the additional expense of doing otherwise.</p><p>　　In the analysis of grade and grade control, o

35、ne of the most important considerations is the effect of grades on the operating costs of the motor vehicle. An increase in gasoline consumption and a reduction in speed are apparent when grades are increase in gasoline

36、consumption and a reduction in speed is apparent when grades are increased. An economical approach would be to balance the added annual cost of grade reduction against the added annual cost of vehicle operation without g

37、rade reduction.</p><p>　　While maximum grades vary a great deal in various states, AASHTO recommendations make maximum grades dependent on design speed and topography. Present practice limits grades to 5 per

38、cent of a design speed of 70 mph. For a design speed of 30 mph, maximum grades typically range from 7 to 12 percent, depending on topography. Wherever long sustained grades are used, the designer should not substantially

39、 exceed the critical length of grade without the provision of climbing lanes for slow-moving vehic</p><p>　　Long sustained grades should be less than the maximum grade on any particular section of a highway.

40、 It is often preferred to break the long sustained uniform grade by placing steeper grades at the bottom and lightening the grade near the top of the ascent. Dips in the profile grade in which vehicles may be hidden from

41、 view should also be avoided. Maximum grade for highway is 9 percent. Standards setting minimum grades are of importance only when surface drainage is a problem as when water must b</p><p>　　3. Sight Distanc

42、e</p><p>　　For safe vehicle operation, highway must be designed to give drivers a sufficient distance or clear version ahead so that they can avoid unexpected obstacles and can pass slower vehicles without d

43、anger. Sight distance is the length of highway visible ahead to the driver of a vehicle. The concept of safe sight distance has two facets: “stopping” (or “no passing”) and “passing”.</p><p>　　At times large

44、 objects may drop into a roadway and will do serious damage to a motor vehicle that strikes them. Again a car or truck may be forced to stop in the traffic lane in the path of following vehicles. In dither instance, prop

45、er design requires that such hazards become visible at distances great enough that drivers can stop before hitting them. Further more, it is unsafe to assume that one oncoming vehicle may avoid trouble by leaving the lan

46、e in which it is traveling, for this might res</p><p>　　Stopping sight distance is made up of two elements. The first is the distance traveled after the obstruction comes into view but before the driver appl

47、ies his brakes. During this period of perception and reaction, the vehicle travels at its initial velocity. The second distance is consumed while the driver brakes the vehicle to a stop. The first of these two distances

48、is dependent on the speed of the vehicle and the perception time and brake-reaction time of the operator. The second distance dep</p><p>　　On two-lane highways, opportunity to pass slow-moving vehicles must

49、be provided at intervals. Otherwise capacity decreases and accidents increase as impatient drivers risk head-on collisions by passing when it is unsafe to do so. The minimum distance ahead that must be clear to permit sa

50、fe passing is called the passing sight distance. In deciding whether or not to pass another vehicle, the driver must weigh the clear distance available to him against the distance required to carry out the sequen</p&g

51、t;<p>　　The geometric design is to ensure highway traffic safety foundation, the highway construction projects around the other highway on geometric design, therefore, in the geometry of the highway design process

52、, if appear any unsafe potential factors, or low levels of combination of design, will affect the whole highway geometric design quality, and the safety of the traffic to bring adverse impact. So, on the geometry of the

53、highway design must be focus on.</p><p><b>　　公路幾何設(shè)計(jì)</b></p><p>　　公路是供汽車或其他車輛行駛的一種線形帶狀結(jié)構(gòu)體。它是由路基、路面、橋梁、涵洞和隧道組成。此外，它還有路線交叉、防護(hù)工程和交通工程及沿線設(shè)施。</p><p>　　路基是路面、路肩、邊坡、邊溝等部分的基礎(chǔ)。它是按

54、照路線的平面位置在地面上開挖和填筑成的土石料構(gòu)造物。路基作為行車部分的基礎(chǔ)，必須保證它有足夠的強(qiáng)度和穩(wěn)定性，可以防止水及其他自然災(zāi)害的侵蝕。</p><p>　　路面是公路表面的部分。它是用混合料鋪筑的單層或多層結(jié)構(gòu)物。路面要求光滑，具有足夠的強(qiáng)度，穩(wěn)定性好和抗?jié)窕δ?。路面質(zhì)量的好環(huán)，直接影響到行車的安全性、舒適性和通行。</p><p>　　公路幾何線形設(shè)計(jì)要考慮公路平面線形、縱斷面線

55、形兩種線形以及橫斷面的組成相協(xié)調(diào)，還要注意視距的暢通等等。確定公路幾何線形時，在考慮地形、地物、土地的合理利用及環(huán)境保護(hù)因素時，要充分利用公路幾何組成部分的合理尺寸和線形組合。</p><p><b>　　1、線形設(shè)計(jì)</b></p><p>　　道路的線形反映在平面圖上是由一系列的直線和與直線相連的圓曲線構(gòu)成的?，F(xiàn)代設(shè)計(jì)時常在直線與圓曲線之間插入緩和曲線。</

56、p><p>　　線形應(yīng)是連續(xù)的，應(yīng)避免平緩線形到小半徑曲線的突變或者長直線末端與小半徑曲線相連接的突然變化，否則會發(fā)生交通事故。同樣，不同半徑的圓弧首尾相接（曲線）或在兩半徑不同的圓弧之間插入短直線都是不良的線形，除非在圓弧之間插入緩和曲線。長而平緩的曲線在任何時候都是可取的，因?yàn)檫@種曲線線形優(yōu)美，將來也不會廢棄。然而，雙向道路線形全由曲線構(gòu)成也是不理想的，因?yàn)橐恍{駛員通過曲線路段時總是猶豫。長而緩的曲線應(yīng)用在拐角

57、較小的地方。如果采用短曲線，則會出現(xiàn)“扭結(jié)”。另外，線路的平、縱斷面設(shè)計(jì)應(yīng)綜合考慮，而不應(yīng)只顧其一，不顧其二，例如，當(dāng)平曲線的起點(diǎn)位于豎曲線的頂點(diǎn)附近時將會產(chǎn)生嚴(yán)重的交通事故。</p><p>　　行駛在曲線路段上的車輛受到離心力的作用，就需要一個大小相同方向相反的由超高和側(cè)向磨擦提供的力抵消它，這些控制值對于某一規(guī)定設(shè)計(jì)車速可能采用曲線的曲率作了限制。通常情況下，某一圓曲線的曲率是由其半徑來體現(xiàn)的。而對于線形設(shè)

58、計(jì)而言，曲率常常通過曲線的程度來描述，即100英尺長的曲線所對應(yīng)的中心角，曲線的程度與曲線的半徑成反比。</p><p>　　公路的直線地段設(shè)置正常的路拱，而曲線地段則設(shè)置超高，在正常斷面與超高斷面之間必須設(shè)置過渡漸變路段。通常的做法是維持道路每一條中線設(shè)計(jì)標(biāo)高不變，通過抬高外側(cè)邊緣，降低內(nèi)側(cè)邊緣以形成所需的超高，對于直線與圓曲線直接相連的線形，超高應(yīng)從未到達(dá)曲線之前的直線上開始，在曲線頂點(diǎn)另一端一定距離以外達(dá)到

59、全部超高。</p><p>　　如果車輛以高速度行駛在直線與小半徑的圓曲線相連的路段，行車是極不舒服。汽車駛近曲線路段時，超高開始，車輛向內(nèi)側(cè)傾斜，但乘客須維持身體的垂直狀態(tài)，因?yàn)榇藭r未受到離心力的作用。當(dāng)汽車到達(dá)曲線路段時，離心力突然產(chǎn)生，迫使乘客向外傾斜，為了維持平衡，乘客必須迫使自己的身體向內(nèi)側(cè)傾斜。由于剩余超高發(fā)揮作用，乘客須作進(jìn)一步的姿勢的調(diào)整。當(dāng)汽車離開曲線時，上述過程剛好相反。插入緩和曲線后，半徑從

60、無窮大逐漸過渡到圓曲線上的某一固定值，離心力逐漸增大，沿緩和曲線心設(shè)置超高，離心力平穩(wěn)逐漸增加，避免了行車顛簸。</p><p>　　緩和曲線在鐵路上已經(jīng)使用多年，但在公路上最近才得以應(yīng)用，這是可以理解的?；疖嚤仨氉裱_的運(yùn)行軌道，采用緩和曲線后，上述那種不舒服的感覺才能消除。然而，汽車司機(jī)在公路上可以隨意改變側(cè)向位置，通過迂迴進(jìn)入圓曲線來為自己提供緩和曲線。但是在一個車道上（有時在其他車道上）做這種迂迴行駛是

61、非常危險的。設(shè)計(jì)合理的緩和曲線使得上述迂迴沒有必要。主要是出于安全原因，公路部門廣泛采用了緩和曲線。</p><p>　　對于半徑相同的圓曲線來說，在未端加上緩和曲線就會改變曲線與直線的相關(guān)位置，因此應(yīng)在最終定線勘測之前應(yīng)決定是否采用緩和曲線。一般曲線的起點(diǎn)標(biāo)為PC或BC，終點(diǎn)標(biāo)為PT或EC。對含有緩和曲線的曲線，通常的標(biāo)記配置增為：TC、SC、CS和ST。對于雙向道路，急彎處應(yīng)增加路面寬度，這主要基于以下因素：

62、（1）駕駛員害怕駛出路面邊緣；（2）由于車輛前輪和后輪的行駛軌跡不同，車輛有效橫向?qū)挾燃哟螅唬?）車輛前方相對于公路中線傾斜而增加的寬度。對于寬度為24英尺的道路，增加的寬度很小，可以忽略。只有當(dāng)設(shè)計(jì)車速為30mile/h，且曲度大于22℃時，加寬可達(dá)2英尺。然而，對于較窄的路面，即使是在較平緩的曲線路段上，加寬也是很重要推薦加寬值及加寬設(shè)計(jì)見《公路線形設(shè)計(jì)》</p><p><b>　　2、縱坡線&l

63、t;/b></p><p>　　公路的豎向線形及其對車輛運(yùn)行的安全性和經(jīng)濟(jì)性的影響構(gòu)成了公路設(shè)計(jì)中最重要的要素之一。豎向線形由直線和豎向拋物線或圓曲線組成，稱為縱坡線?？v坡線從水平線逐漸上升時稱為坡度變化的影響。</p><p>　　在確定坡度時最理想的情況是挖方與填方平衡，沒有大量的借方或棄方。所有運(yùn)土都盡可能下坡運(yùn)并且距離不長，坡度應(yīng)隨地形而變，并且與既有排水系統(tǒng)的升、降方向一致

64、。在山區(qū)，坡度要使得挖填平衡以使總成本最低。在平原或草原地區(qū)，坡度與地表近似平行，介是高于地表足夠的高度，以利于路面排水，苦有必要，可利用風(fēng)力來清除表面積雪。如公路接近或沿河流走行，縱坡線的高度由預(yù)期洪水位來決定。無論在何種情況下，平緩連續(xù)的坡度線要比由短直線段連接短豎曲線構(gòu)成的不斷變向的坡度線好得多。</p><p>　　由上坡向下坡變化的路段應(yīng)設(shè)在挖方路段，而由下坡向上坡變化的路段應(yīng)設(shè)在填方路段，這樣的線形設(shè)

65、計(jì)較好，往往可以避免形成與現(xiàn)狀地貌相反的圭堆或是凹地。與挖填方平衡相比，在確定縱坡線時，其他考慮則重要得多。</p><p>　　城市項(xiàng)目通常比農(nóng)村項(xiàng)目要求對控制要素進(jìn)行更詳盡的研究，對高程進(jìn)行更細(xì)致地調(diào)整。一般來說，設(shè)計(jì)與現(xiàn)有條件相符的坡度較好，這樣可避免一些不必要的花費(fèi)。</p><p>　　在坡度的分析和控制中，坡度對機(jī)動車運(yùn)行費(fèi)用的影響是最重要的考慮因素之一。坡度增大油耗顯然增大，

66、車速就要減慢。一個較為經(jīng)濟(jì)的方案則可使坡度減小而增加的年度成本與坡度不減而增加的車輛運(yùn)行年度成本之間相平衡。這個問題的準(zhǔn)確方法取決于對交通流量和交通類型的了解，這只有通過交通調(diào)查才能獲知。</p><p>　　在不同的州，最大縱坡也相差懸殊，AASHTO標(biāo)準(zhǔn)建議由設(shè)計(jì)車速和地形來選擇最大縱坡?，F(xiàn)行設(shè)計(jì)以設(shè)計(jì)車速為70mile/h時最大縱坡為5%，設(shè)計(jì)車速30mile/h時，根據(jù)地形不同，最大縱坡一般為7％－12％

67、。當(dāng)采用較長的待續(xù)爬坡時，在沒有為慢行車輛提供爬坡道時，坡長不能夠超過臨界坡長。臨界坡長可從3％縱坡的1700英尺變化至8%縱坡的500英尺。</p><p>　　持續(xù)長坡的坡度必須小于公路任何一個斷面的最大坡度，通常將長的持續(xù)單一縱坡斷開，設(shè)計(jì)成底部為一陡坡，而接近坡頂則讓坡度減小。同時還要避免由于斷面傾斜而造成的視野受阻。調(diào)整公路的最大縱坡為9%只有當(dāng)路面排水成問題時，如水必須排至邊溝或排水溝，最小坡度標(biāo)準(zhǔn)才

68、顯示其重要性。這種情況下，AASHTO標(biāo)準(zhǔn)建議最小坡度為0.35%。</p><p><b>　　3、視距</b></p><p>　　為保證行車安全，公路設(shè)計(jì)必須使得駕駛員視線前方有足夠的一段距離，使他們能夠避讓意外的障礙物，或者安全地超車。視距就是車輛駕駛員前方可見的公路長度。安全視距具有兩方面含義：“停車視距”或“不超車視距”或“超車視距”。</p>

69、<p>　　有時，大件物體也許會掉到路上，會對撞上去的車輛造成嚴(yán)重的危害。同樣，轎車或卡車也可能會被一溜車輛阻在車道上。無論是哪種情況發(fā)生，合理設(shè)計(jì)要求駕駛員在一段距離以外就能看見這種險情，并在撞上去之前把車剎住。此外，認(rèn)為車輛通過離開所行駛的車道就可以躲避危險的想法是不安全的，因?yàn)檫@會導(dǎo)致車輛失控或與另一輛車相撞。</p><p>　　停車視距由兩部分組成：第一部分是當(dāng)駕駛員發(fā)現(xiàn)障礙物面作出制動之

70、前駛過的一段距離，在這一察覺與反應(yīng)階段，車輛以其初始速度行駛；第二部分是駕駛員剎車后車輛所駛過的一段距離。第一部分停車視距取決于車速及駕駛員的察覺時間和制動時間。第二部分停車視距取決于車速、剎車、輪胎、路面的條件以及公路的線形的坡度。</p><p>　　在雙車道公路上，每間隔一定距離，就應(yīng)該提供超越慢行車輛的機(jī)會。否則，公路容量將降低，事故將增多，因?yàn)榧痹锏鸟{駛員在不能安全超車時冒著撞車危險強(qiáng)行超車，能被看清的

71、允許安全超車的前方最小距離叫做超車視距。駕駛員在做出是否超車的決定時，必須將前方的能見距離與完成超車動作所需的距離對比考慮。影響他做出決定的因素是開車的小心程度和車輛加速性能。由于人與人的顯著差別，主要是人的判斷和動作而不是力學(xué)定理決定的超車行為隨著駕駛員的不同而大不相同。</p><p>　　公路幾何設(shè)計(jì)是確保公路交通安全的基礎(chǔ)，公路建設(shè)的其他項(xiàng)目都圍繞公路的幾何設(shè)計(jì)而展開，因此，在公路的幾何設(shè)計(jì)過程中，如果出