二級公路設(shè)計專業(yè)外文翻譯-公路隧道(存儲版)
【正文】 roadways, the added width is so small that it can be neglected. Only for 30mph design speeds and curves sharper than 22176。 curved sections are super elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center line 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. If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp circular curve, riding is extremely unfortable. As the car approaches a curve, super elevation begins and the vehicle is tilted inward, but the passenger must remain vertical since there is on centrifugal force requiring pensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider outward from his vertical position. To achieve a position of equilibrium he must force his body far inward. As the remaining super elevation takes effect, further adjustment in position is required. This process is repeated in reverse order as the vehicle leaves the curve. When easement curves are introduced, the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal force also develops gradually. By careful application of super elevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided. 河南理工大學(xué)本科畢業(yè)設(shè)計 專業(yè)外文翻譯 3 Easement curves have been used by the railroads for many years, but their adoption by highway agencies has e only recently. This is understandable. Railroad trains must follow the precise alignment of the tracks, and the disfort described here can be avoided only by adopting easement curves. On the other hand, the motorvehicle operator is free to alter his lateral position on the road and can provide his own easement curves by steering into circular curves gradually. However, this weaving within a traffic lane (but sometimes into other lanes) is dangerous. Properly designed easement curves make weaving unnecessary. It is largely for safety reasons, then, that easement curves have been widely adopted by highway agencies. For the same radius circular curve, the addition of easement curves at the ends changes the location of the curve with relation to its tangents。它是按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。 線形設(shè)計 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。另外，線路的平、縱斷面設(shè)計應(yīng)綜合考慮，而不應(yīng)只顧其一，不顧其二，例如，當平曲線的起點位于豎曲 線的頂點附近時將會產(chǎn)生嚴重的交通事故。當汽車到達曲線路段時，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。設(shè)計合理的緩和曲線使得上述迂迴沒有必要。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)計見《公路線形設(shè)計》 縱坡線 河南理工大學(xué)本科畢業(yè)設(shè)計 專業(yè)外文翻譯 9 公路的豎向線形及其對車輛運行的安全性和經(jīng)濟性的影響構(gòu)成了公路設(shè)計中最重要的要素之一。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。這個問題的準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。這種情況下，AASHTO 標準 建議最小坡度為 %。 停車視距由 兩 部分組成：第一部分是當駕駛員發(fā)現(xiàn)障礙物面作出制動之前駛過的一段距離，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。 公路 幾何 設(shè)計 是確保 公路 交通安全的基礎(chǔ)， 公路 建設(shè)的其他項目都圍繞 公路的 幾何 設(shè)計 而展開，因此，在 公路 的 幾何 設(shè)計 過程中，如果出現(xiàn)任意的不安全潛在因素，或者低水平的組合 設(shè)計 ，都會影響到整個 公路 幾何 設(shè)計 的質(zhì)量，并對交通的安全帶來不利影響。否則，公路容量將降 低，事故將增多，因為急燥的駕駛員在不能安全超車時冒著撞車危險強行超車，能被看清的允許安全超車的前方最小距離叫做超車視距。 有時，大件物體也許會掉到路上，會對撞上去的車輛造成嚴重的危害。臨界坡長可從 3％縱坡的 1700 英尺 變化至 8%縱坡的 500 英尺 。一般來說，設(shè)計與現(xiàn)有條件相符的坡度較好，這樣可避免一些不必要的花費。所有運土都盡可能下坡運并且距離不長，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。對含有緩和曲線的曲線，通常的標記配置增為： TC、 SC、 CS 和 ST。 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 。 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 。長而平緩的曲線 在任何時候都是可取的， 因為這種曲線線形優(yōu)美，將來也不會廢棄。路面要求光滑 ，具有足夠的強度，穩(wěn)定性 好 和抗 濕 滑 功 能。 and the
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