Construction Technique of Bearing Sand Silt with Low Liquid Limit Used as Highway Subgrade

In most cases,bearing sand silt with liquid limit isn't used as the material to building highway subgrades because its compaction is very difficult.The Xin-He Expressway in Yunnan Province is an important road being constructed.On the basis of modern mature building techniques of highway subgrades,the soil can be replaced by some better soil,or modified by adding some stone or such other materials as cement and lime.But both of the two methods will largely increase the cost to building the road because there isn't better and enough soil or stone near the road line.Another bad aspect of the two methods is they may damage environment.Construction technique,which may improve the degree of compaction of the soil,is therefore investigated in this study.According to the climatic condition at the road,the high water content of the soil can be effectively decreased by rabble under sunlight during the period from November to April next year.The results of vibrating compaction tests indicate that when the thickness of loose soil layer is 30 cm and the repeat number of vibrating compaction isn't less than 5,the degree of compaction of the soil can meet the requirements in the specification for construction of highway subgrades.The results of impacting compaction tests indicate that the impacting compaction is useful to increase the degree of compaction of the soil compacted by the vibrating compaction, so it may be used together with the vibrating compaction to improve the degree of compaction of the soil in actual construction of the highway subgrade.