Research On Design Methods Of Expressway Drainage System

Annually many rainfall disasters influenced on expressway transportations and social economy during rain seasons in China. In order to decrease these rainfall disasters losses, a comprehensive and systemic study must been taken in design methods and design parameters of expressway drainage system. Beside these, renewing the deficiencies of computation methods and establishing expressway drainage system calamity appraise system are needed for improving expressway resist ability in rainfall disaster too. Only do these, the service level of expressway should be advanced and the design theoretics for expressway drainage system could be enhanced.Depended on expressway from Huang Ling to Yan'an of ShaanXi province, the topography, geolophy and hydrometeorology conditions in loess donga are surveyed in this paper, moveover, it has analysed the forming theory of runoff, rainfall infiltration rule and the influence of surfacewater and groundwater. On the base of overland flow theory, using the one-dimension kinetic wave model, the formula for overland flow is deduced, which considered configuration and land feature in loess donga. At the same time, according to the fuzzy synthetically evaluation theoretics, evaluating indexes and evaluation criterions, which correspond to expressway drainage facilities, have been raised in the paper, and then integrating the expressway from Huang Ling to Yan'an, it presented the fuzzy evaluation process and made evaluation system more available than before.Next, associated with hydrology and hydraulics theory, the paper summarized the actual criterions and researches, whereafter, it has analysed and perfected the design parameters of expressway drainage system, such as longitudinal gradient for ditch, the prerequisite of discharging sediment and the designed repetition period of rainfall. Furthermore, for the sake of the validity of data, the paper has ameliorated some computation methods, for instance, hydraulic radius, permissible velocity correction factors, the flux of incomplete underdrain, rainfall intensity-duration-frequency model (IDF model). In addition, as the proverb said: "In fair wearher prepare for foul", the paper propounded establishing effective calamity appraise system for expressway drainage system and put forward calamity appraise indexes system.