Study On The Subgrade Drainage Facilities Of Rural Highway

Water is one of the major factors which causes roads to be destroyed. The defect in drainage facilities is one of the important reasons to the water diseases of roads. Up till now there are not a design specification or design guide developed specialized for rural highways, and the drainage facilities of rural highways can not be constructed absolutely according to the Specifications of Drainage Design for Highways. Because rural highways have low volume and are lack of construction money, the practical and cheap drainage facilities need be developed.The author conducted a survey on the drainage facilities for subgrade of rural highways in nine typical provinces across China such as Liaoning Province, Guangdong Province, Hubei Province, Sichuan Province and Gansu Province. Many practical and cheap drainage facilities were used, and the virtues and defects of many drainage facilities were discussed.According to the survey results and the requirements of Specifications of Drainage Design for Highways, considering the low importance and low cost of rural highways, the autohr gave the hydrologic and hydraulic formula and determined the parameters, such as the scheduled time of flood appearance and the design flood frequency. The author recommended the drainage facilitiess for subgrade of the rural highways in mountain area, villages and the area rich in water, where the low traffic volume and cost of rural highways and the development level of economy and annual precipitation of different regions were considered. In villages, the author recommended the drainage facilities without side ditches, with unpaved ditches, with paved ditches which were not covered, and with paved ditches which were covered; in the area rich in water five kinds of drainage facilities were recommended; and in some difficulty mountain area, the drainage facilities were recommended to be designed specially.