Research On Settlement Analysis And Treatment Countermeasures Of Highway Soft Soil Subgrade

Soft soil has the characteristics of high natural water content,large natural void ratio,high compressibility,low shear strength,long consolidation time,large disturbance,poor permeability,etc.The engineering geological conditions are poor.Therefore,for highway engineering construction,the settlement and stability of soft soil subgrade is a basic and hot issue in this field.In the stage of road design and construction,geological conditions,types of subgrade fillings,embankment filling height,filling rate,construction methods and treatment methods of foundation will affect the bearing capacity of subgrade,which may lead to uneven settlement.In the stage of road operation,a large number of traffic cyclic loads aggravate the additional stress in the subgrade,aggravate the settlement deformation,cause pavement damage,and then cause traffic accidents.The above factors interact with each other and need to be systematically analyzed and quantified.For this reason,this study takes a grade road in Linfen City of Shanxi Province as the research object.From the original geological conditions,roadbed and pavement structure,traffic load and other aspects,the settlement law of soft soil roadbed and its treatment methods are studied.The main contents are as follows:(1)Starting from the specific situation of the project,through field investigation,geological exploration and geotechnical test,the characteristics and related physical parameters of the soft soil roadbed in this area are analyzed,which provides a basis for the stress analysis and settlement calculation of the soft soil subgrade in the future.(2)In order to quantify the stress of soft soil roadbed,the stress distribution of roadbed under standard load and overload is studied by calculating the self-weight stress of roadbed and the additional stress caused by vehicle load.Considering that vehicle load is concentrated load and uniform load,the stress distribution of roadbed under standard load and overload is studied.At the same time,the influence of traffic load on foundation stress is analyzed.(3)On the basis of the above stress analysis,the settlement of roadbed caused by roadbed dead weight and traffic load is calculated.The existing modulus of compression method does not consider the subgrade as a whole in calculating the load and settlement of foundation for layered fill.Therefore,an improved modulus of compression method is proposed,which considers the subgrade as a whole and more in line with the actual situation of traffic load.(4)In order to reduce the settlement of roadbed,according to the actual situation of the project,the paper studies the drainage of roadbed and pavement,the compaction of roadbed and the treatment of soft soil foundation.Firstly,according to the cross-section of the road,several drainage facilities schemes are given;secondly,the construction technology of road foundation filling in construction stage is given;lastly,for some soft soil areas,the advantages and disadvantages of sand cushion method,replacement method,cement fly ash gravel pile method(CFG pile method)are compared comprehensively,and CFG pile method is chosen as the treatment scheme,and the rock and soil foundation treatment software is adopted.The analysis and calculation are carried out.In summary,this paper studies the stress analysis,settlement calculation and treatment scheme of the roadbed from the practice of a project,and obtains the stress distribution law and specific design scheme of the soft soil roadbed,which can effectively reduce the settlement of the roadbed.On the one hand,this study can provide a specific scheme for the actual project,but also can provide a reference for the analysis of soft soil roadbed under the relevant terrain conditions.