Study On Treatment Methods And Behavior Of Gravel Compaction Column Composite Foundation In Saline Soft Soil Area

Northwest China has the most widely saline soil distributed. Saline soil is harmful toexpressway engineering, such as salt expansion, dissolve falling, frost boiling, corrosion,deformation and so on., To treat saline soil ground under embankment of freeway is necessarywith the advance of Western Development. Gravel compaction column is a type of importantmethods, which has many advantages, such as good reinforcement effect, convenientoperation and less expense. Research achivemengts of the dissertation include additionalstress and deformation characteristics of gravel compaction column composite ground underembankment in saline soil area, based on indoor tests, in-situ tests, FLAC3D numericalsimulation and theoretical analysis.The main research achievements of the dissertation include:(1) Construction techniques and construction equipments of gravel compaction columnare introduced according to this engineering.How salt content effect on engineering propertyis induced and analyzed accroding to informed research. The characteristics of soft soilfoundation under embankment load of freeway is also summarized. And problems exsited inthe literatures are discussed.(2) The load transfer mechanism and additional stress distribution behavior of gravelcompaction column composite ground under embankment is studied based on fast lagrangiananalysis of continua (3D) numerical simulation. The variation rule of axial force and lateralfriction resistance with depth is analyzed. The results indicate that the gradient of additionalstress is relatively high at the top of column and the end compareed with the naturalfoundation. The column can undertake more loads and effectively reduce settlement underembankment.(3) The ground settlement and lateral displacement characteristics of gravel compactioncolumn composite ground under embankment is studied based on fast lagrangian analysis of continua (3D) numerical simulation. Settlement of column and settlement of soil betweencolumns are inequality under enmbankment loads. The mechanism of addtion stressdistributions and diversion of soils and columns under embankment load is affected by thedifferential settlement. And settlement of column and settlement of soil between coloumsincrease as embankment rises, then stabilize gradually after embankment finishing. The curveof lateral deformations along the depth is bow style. Lateral deformation increase withembankment loads raise, then decreases immediately while embankment loads standing,stabilize gradually at last when embankment load finished.(4) The effect of gravel compaction column under embankment in saline soil area isreserched according to engineering practice. Additional stress distribution behavior anddeformation characteristics of gravel compaction column composite ground underembankment are researched according to in-situ tests. The test results coincide with resultscalculated by3D numerical simulation.