Study On Comprehensive Treatment Technology Of Alluvial Soil Subgrade In Beibu Gulf Offshore

This paper relies on the subgrade engineering of no.7 contract section of guigang-hepu expressway in Guangxi,aims at the problem of insufficient strength,compaction control and evaluation that offshore estuarine alluvial soil in this section exists when the soil is used as subgrade filler,and combines the physical and mechanical testing and theoretical analysis methods of alluvial soil,proposes the improved techniques and integrated treatment measures for alluvial soil.First of all,the granule composition of the alluvial soil in this area have been analyzed through the method that use of sodium pyrophosphate as dispersant to destroy the constitutive property of the soil,and the fine grained soil below 0.075mm have been used for both liquid and plastic limit tests and test that analyze the effects of different particle composition and constitutive property on CBR and so forth,and the basic properties of fluvial soil as a kind of complex mixed soil have been investigated.Secondly,due to the variability of physical indexes of alluvial soil,the traditional standard dry density is difficult to accurately evaluate the degree of compaction.So the method has been proposed that use the pore ratio to characterize the compacted density of the soil and the standard and method of compaction control based on porosity ratio and saturation,this methods play an active role in solving the compaction control problem on site.What's more,this paper focuses on the mechanism and method of physical improvement of alluvial soil,and the effects of mixing coarse or fine grains on physical properties and CBR of improved soils,determines the appropriate blending ratio.the mechanism and reasonable proportion of cement-improved alluvial soil were studied at the same time.The methods of physical and chemical improvement have been used to fill the test section,the field test shows that the test section basically meets the requirement of subgrade stability.Finally,this paper aims at the problem of slope erosion,road bed softening,constitutive property backfilling subsidence,seepage across the subgrade and so on that alluvial soil exists when the soil is used as subgrade filler,raises targeted comprehensive treatment engineering measures,improves the overall stability and durability of the subgrade.This paper has a certain reference value for the future research on reducing the variability of offshore alluvial soil,reasonably utilizing the constitutive property of soil,and further controling the soil's wetting and softening properties.