Research On The Mechanism Of Mechanical Property Change In Landfill Soil Under The Freeze-Thaw Cycle

In the northern region of China,the climate varies markedly from season to season.With the change of seasons and temperature,the freeze-thaw process will occur again and again,and each freeze-thaw process will have a certain impact on the property parameters of the soil,thus bringing hidden dangers to the stability and safety of the project.Now because of the social rapid development,the garbage output doubled year by year.In order to deal with the rubbish better,the landfill has become a necessary engineering facility in the city.The soil freeze-thaw cycle problem in landfills can make landfills produce differential settlement,which will bring some negative impact on the overall stability of the landfill.In order to study the changing patterns and mechanism of soil mechanical properties after freeze-thaw cycle in landfills and the differential settlement in landfills,this paper uses the method of combination of test procedure and numerical simulation.After field sampling,measure the change in mechanical properties of garbage soil by garbage soil freeze-thaw cycle test and triaxial test,and analyze its mechanism.Then bring the data into FLAC 3D numerical simulation software and conduct the simulation of differential settlement of Jinzhou city Nanshan landfill under freeze-thaw cycles.The whole process provides scientific theory basis for practical engineering work.In the test,the moisture content of the samples has been setting for 40%,50% and 60%.Freezing temperature has been setting for-10?,-15? and-20?.Freeze-thaw cycle has been setting for 0,1,3,6,9,12 times.By test procedure and numeral simulation,the following conclusions are drawn:(1)When the moisture content and freezing temperature of garbage soil are constant,the values of cohesion and elastic modulus of garbage soil will continue to decrease with the increasing number of freeze-thaw cycle.When the freeze-thaw cycle reaches 6 times,the cohesive force and elastic modulus decrease gradually.However,there is no definite rule for the change of friction angle in waste soil.At this point,the shear strength decreases with the increasing number of freeze-thaw cycles.When the number of freeze-thaw cycles reaches 12,the shear strength decreases to a smaller extent and gradually reaches a stable state.(2)When the number of freeze-thaw cycles and freezing temperature are constant,the cohesive force,internal friction Angle and elastic modulus of garbage soil will all decrease with the increase of moisture content,so will its shear strength.(3)When the number of freeze-thaw cycles and moisture content are constant,the cohesion and elastic modulus of garbage soil will decrease with the decrease of freezing temperature,but internal friction Angle will increase slightly,and the shear strength will decrease.(4)After 1,3,6,9,12 times of freeze-thaw cycle of landfill soil,the maximum subsidence resulting from freeze-thaw cycle were 0.19 m,0.61 m,1.26 m,2.02 m and 2.53 m respectively.The maximum settlement occurs in the high elevation area,and the highest differential settlement occurs around the corner of the landfill,whereas the lowest occurs in the middle.The value and the rates of differential settlement can continuously fluctuate when the location is different,but the overall trend is similar.(5)In the process of landfill,the method of layered landfill is adopted,and the original waste body is rolled by large compaction machinery;A liner system with geogrid can be arranged between each layer of garbage body;Leachate recharge can be used to accelerate the settlement of landfill.After field sealing,fly ash can be used for perfusion treatment.