一般路基设计（General roadbed design）.docVIP

一般路基设计（General roadbed design） Section 3 design of roadbed 1. General roadbed design content (1) select the roadbed section type to determine the width of the roadbed and the height of the roadbed; (2) selecting roadbed packing and compacting criteria; (3) to determine the shape and grade of the slope; (4) layout and drainage structure design of roadbed drainage system; (5) slope protection and reinforcement design; (6) ancillary facilities design. 2. Roadbed width design (1) the concept of roadbed width: the width of roadbed width is the sum of the width of the carriageway, the shoulder, the middle belt, the change lane, and the roadway, which is generally understood as the distance between the outer edge of the earthen shoulder. (2) the principle of determining roadbed width: occupation of land and ecological balance problem must be considered, should be accounted for as little as possible, consider digging farmland balance in order to reduce soil excavation, prevent water loss and soil erosion in order to maintain the ecological balance. Figure 3-6 road base width chart A) highways and highway b) two, three, four - level highways (3) determination of roadbed width (1) carriageway: 3.5-3.75m, related to the width of the vehicle, design traffic volume, traffic composition and speed of the car; (2) shoulder: the plain micromound area of the highway and the first level road, the shoulder width should be more than 2.50 m when the conditions are available. (3) intermediate belt: the minimum middle band width varies with the highway grade and the terrain conditions at 2.50 m ~ 4.50 m, which can be reduced to 2.00 m in special cases. The width of the belt in the middle is wider than the width of the belt, which can be used to avoid the width of the set width of the roadway, such as the guardrail, anti-dazzle network and cross road. (4) variable speed lane: highway and first level highway, when the slope is greater than 4%, the slope lane can be located along the upper sl