Compared Study On The Methods Of Highway Sub-grade Widening In Cold Areas

In recent years, with the rapid development of the economy in our country, some of the highways can not meet the ever-growing traffic loads. Therefore, there is a rising tendency in the number of the projects of highway reconstruction and extension. Among the many engineering tasks, sub-grade widening is a focal one. If the combination of the old sub-grades and the new ones is not properly disposed, then the quality of the projects will face serious threatsThe sub-grade widening in used highway reconstruction and extension projects in cold areas shares the general features of all the highway reconstruction and extension engineering in other zones, and at the same time it also has its special features which are caused by the climatic and environmental factors.This paper starts with the keystone phenomena in sub-grade widening in used highway reconstruction and extension project in cold zone. These various damaged phenomena include asymmetric sedimentation, asymmetric swelling and contracting, and soft groundwork the old sub-grades and the new ones. Then the paper analyzes the special methods in widening, the mechanism and the causes and the influential factors of those damages, and also analyzes the corresponding engineering methods. With the data from the finished projects, the paper attempts to make a compared study of different methods.Based on the gray system theory, it calculates the degrees of relevancy and thus orders the indexes for the factors in respect of degree of relevancy in sub-grade widening in cold areas. From this method, the degree of effect for those indexes can be educed in widening engineering and effective methods can thus be taken accordingly.The last part of this paper is the conclusion and further perspectives.