Research on design parameters of highway drainage system

In order to solve the problem of choice of longitudinal gradient for ditch with multiple longitudinal profiles, the concept of namely design longitudinal gradient for ditches was put forward, and corresponding formula was given. According to the structure importance, damage consequence, repair readability, service requirements and relevant overseas stipulations related to various types of ditches, the designed repetition period of rainfall and proposed safety depth values for ground drainage facilities within road margin were proposed. In addition, the relationship between the prerequisite of discharging sediment in ditches or conduits and minimum longitudinal gradient was discussed, and the amendment suggestions to corresponding stipulations as stated in current specification of highway drainage design were advanced. The study can be directly used in the design of highway drainage, and also can provide technical support for sequential amendment to specification.