Research On Mechanical Properties And Damage Model Of Fly Ash Stabilized Saline Soil Under Freeze-thaw Cycle

The saline soil area in northeast Songnen Plain is the largest alkaline saline soil area in China.The engineering characteristics of the saline soil are poor,which is easy to cause salt swelling and subsidence.Moreover,due to the high cold climate environment in Northeast China,the saline soil is affected by freeze-thaw action year after year,which is prone to frost heave and thaw subsidence.With the rapid development of economic construction in recent years,more and more projects will be carried out in Northeast saline soil area.It is inevitable to consider the double effects of saline soil and freeze-thaw cycle.In view of this kind of engineering problem,among many solutions,improving saline soil is not only economical,but also easy to construct and wide range of application.Therefore,it is of great significance to study the improvement of saline soil under the action of freeze-thaw cycle.Based on SKLFSE201919,a key laboratory project of Frozen Soil Engineering in Northeast China,this paper takes the artificially configured carbonated soil as the research object,and uses lime and fly ash to improve the saline soil,and carries out unconfined compressive tests and triaxial shear tests.The influences of temperature,dosage of curing agent,moisture content,compacting degree,confining pressure and number of freeze-thaw cycles on mechanical properties of improved saline soil were investigated.According to the test results,the following main results are obtained: lime and fly ash can significantly improve the compressive strength of carbonate soil,and the curing effect of carbonate soil is the most significant when 3% lime and 12% fly ash are added.Temperature and loading rate significantly affect the compressive strength and elastic modulus of cementation soil,and the relationship between them can be expressed as a function.The mechanical properties of improved soil can be greatly reduced by freeze-thaw cycle.The compressive strength and elastic modulus of solidified soil decrease the most after the first freeze-thaw cycle,and then tend to be stable.The samples with low water content and high soil compactness are less affected by freeze-thaw action.There is a nonlinear relationship between soil moisture content,compacting degree and freeze-thaw cycles and compressive strength.The freeze-thaw cycle can decrease the shear strength of the improved saline soil,and the cohesion and internal friction Angle decrease with the increase of the number of freeze-thaw cycles.The damage model can well express the variation trend of soil stress and has certain reference value for practical engineering application.The three-parameter two-ash solidified saline-soil damage model based on neural network has better prediction accuracy and is convenient to use.