The Study Of Subgrade Height For Highway In Plain Area

The high subgrade of the constructed highway in plain area causes mass.occupation of land. Besides, with per capita and resource smallness and more and more attention payed on concept of land saving, what measures to take to decrease the height of subgrade and what extent to reduce to is becoming research focus recently.Based on analysis on influencing factors, the article classify influencing factors into natural influencing factors, technique influencing factors, economic influencing factors and others, and find out major restricting factors of the subgrade height decreasing, analyses, and think that main measure of decreasing the height of subgrade should start with economic influencing factors. Meantime, detailed research is taked aiming at bottleneck problem of restricting subgrade height—Elevation question in channel. This article researched the drainage system of channel, include the setting of waterproof canopy, reservoir(evaporation pool), pumping station and so on. The article also studied size design, economic benefits, advantages and disadvantages, and application scope of the drainage facilities. The conclusion show that the drainage problem could be solved commendably, and then the channel can be dipped low enough than the ground. These could decrease the highway subgrade height in channel completely.Aiming at how to define the subgrade height of highway in plain area, the article set up a evaluating model based on grey system theory to the estimate different subgrade height. Through classifying the factors influencing subgrade height again, select appropriate factors to built up guideline system for evaluating model. And calculate and compare the correlation degree of different subgrade height to educe the best subgrade height. The article evaluated subgrade heights of 9 about South-Jiqing project. The conclusion show that the subgrade height at 1.0m is best, and subgrade height range at 1.0m～1.5m is better.At last, the article set up the design flow to educe the best subgrade height of highway in plain area according to idiographic project., and then applied it in South-Jiqing project vertical design. Through comparing the guidelines of line.type and economic, validated the better subgrade height range, and commend the subgrade height in project is 1.4m.