山区公路平面线形的优化设计

作为动态规划法与随机搜索法相结合进行公路线形优化设计的应用之一,本文提出了在山区狭长地带范围内对公路平面线形进行优化的有效方法。本方法选用了简单实用的带状方格网式数字地形模型。线形优化的目标函数采用以主导坡度控制时的“理想坡度线”作为纵断面设计线的假想工程量或假想工程费用。函数的状态变量和决策变量为平面转角点座标。一般情况下,优化的计算单元包含了圆曲线和缓和曲线的构成,并选用各转角点的直缓点作为分段点。此外,文中还列举了进行公路平面和纵断面线形优化前后的算例比较与成果分析。算例表明,采用本方法进行山区公路平面线形优化通常能缩短路线,增大平曲线半径和提高路线设计纵坡的均匀性,并明显降低工程造价。

Optimisaton of the Plan View of Highway Configuration in Mountainous Areas

This article presents an effective method, using the combination of dynamic programming and stochastic process for optimisation of the plan view of highway configuration in long narrow zones of land in mountainous areas. A simple and practical digital topographic model of the band-formed grid method has been chosen. The hypothetic volume of constructional work or the hypothetic expenses incurred, with the "ideal slope line" being taken as the elevation design line, is used as the target-function of the optimisation of highway configuration. The state-vector and assessment-vector of the function are the coordinates of the polygon points of the plan view. Normally the elements of optimisation calculations include the construction of round curves clothoid and straight line, and the connecting points of straight lines and clothoid in various polygon points are chosen as landmarks for different road sections. For purposes of comparison, this article also presents examples of calculating and analysing results of the plan view and longitudinal sectional view of highway configuration before and after optimisation. The results of the examples indicate that this method, if employed in the optimisation of the plan view of highway configuration in mountainous areas, will generally shorten the length of highway, increase the radius of curvature, improve the uniformity of longitudinal slope and considerably reduce the cost of construction.