【導讀】偃師顧縣至黃蟒崖段公路路線起點連接G310、省道S320顧龍線，是洛陽至偃師的主要交通要道。它的建成對全國公路網(wǎng)絡結(jié)構(gòu)的完善，對加快城市與城市之間經(jīng)濟社會發(fā)展具有極其重要的意義。擬建的偃師顧縣至黃蟒崖段公路，經(jīng)過區(qū)域地貌為伊南洪積沖積坡地、伊洛河沖積平原、洛河川區(qū)、洛陽中部黃土丘陵區(qū)，整個地形起伏不大，。根據(jù)規(guī)范要求，結(jié)合當?shù)貙嶋H情況，全線采用雙向四車道一級公路標準，瀝青路面，設計速度80km/h，。本設計研究的內(nèi)容包括：首先，根據(jù)交通量確定車道數(shù)，并在地形圖上選線、定線，然后進行道路平面設計，縱斷面設計，橫斷面設計，橋涵設置等。此外還對該路段的路基、路面等進行了設計。降水多集中在每年的7、8、9三個月份。受氣候影響，路面施工應避開冬季。路線按照平原微丘區(qū)一級公路進行設計，設計時速為80Km/h；路面采用瀝青路面，設計年限為15年。

　　

【正文】 n 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 superelevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided. 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。 hence the decision regarding their use should be made before the final location survey. They point of beginning of an ordinary circular 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 mon notation is, as stationing increases: TS (tangent to spiral), SC (spiral to circular curve), CS (circular curve to spiral), and ST (spiral go tangent). On twolane 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) increased 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 24ft roadways, the added width is so small that it can be neglected. Only for 30mph design speeds and curves sharper than 22176。does the added width reach 2 ft. For narrower pavements, however, widening assumes importance even on fairly flat curves. Remended amounts of and procedures for curve widening are given in Geometric Design for Highways.B Grades The vertical alignment of the roadway and its effect on the 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 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 analyzing grade and grade controls, the designer usually studies the effect of change in grade on the centerline profile. 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 downhill 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 embankment as a clue toward least overall cost. In flat or prairie country it will be approximately parallel to the ground surface but sufficiently above it to allow surface drainage and, where necessary, to permit the wind to clear drifting snow. Where the road approaches or follows along streams, the height of the grade line may be dictated by the expected level of flood water. Under all conditions, smooth, flowing grade lines are preferable to choppy ones of many short straight sections connected with short vertical curves. Changes of grade from plus to minus should be placed in cuts, and changes from a minus grade to a plus grade should 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 considerations for determining the grade line may be of more importance than the balancing of cuts and fills. Urban projects usually require a more detailed study of the controls and finer adjustment of elevations than do rural projects. It is often best to adjust the grade to meet existing conditions because of the additional expense of doing otherwise. In the analysis of grade and grade control, one 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 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 grade reduction. An accurate solution to the problem depends on the knowledge of traffic volume and type, which can be obtained only by means of a traffic survey. While maximum grades vary a great deal in various states, AASHTO remendations make maximum grades dependent on design speed and topography. Present practice limits grades to 5 percent 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 exceed the critical length of grade without the provision of climbing lanes for slowmoving vehicles. Critical grade lengths vary from 1700 ft for a 3 p