Study On The Improvement Of Soft Clay Foundation Treatment By Artificial Freezing Method

Natural soft clay has a high water content.When it is used as a building foundation,it needs to be drained and consolidated in advance to improve the bearing capacity of the foundation.At present,the more widely used methods of consolidation drainage are: preloading method,vacuum preloading method,electroosmosis method and many joint technologies.However,due to the poor permeability of soft clay,these methods take a long time and the results of the treatment are sometimes difficult to achieve the intended purpose.Therefore,it is very necessary to improve the soft clay ground treatment method.Freezing and thawing is a process that changes the phase of soil moisture.In this process,it will cause structural changes in the soil,increase permeability,and trigger water migration.If it is applied to the treatment of soft clay ground,it should be able to improve the timeliness and degree of consolidation of the drainage process.Therefore this paper has conducted an in-depth study on the feasibility of the application of freeze-thaw cycles in the treatment of soft clay ground.First,the permeability test after the freeze-thaw cycle of saturated soft clay was carried out,the change of the permeability coefficient of the sample was observed,the mechanism of permeability change and the relationship between the freeze-thaw cycle and the treatment of soft clay foundation were analyzed;The sample was scanned with an electron microscope to obtain a microscopic image of the sample.The changes in the microstructure were qualitatively analyzed and the relationship between the microstructure and the physical and mechanical properties of the soil was discussed;A consolidation test was conducted after the freeze-thaw cycle of saturated soft clay.The change of the compression deformation of the sample and the change of the pore water pressure during the consolidation process were observed.The deformation characteristics of the sample under the freeze-thaw cycle and the relationship between the change of the pore water pressure and the water migration were analyzed.Then,an indoor freeze-thaw consolidation model test was carried out to simulate the effects of moisture and structure changes in the soil caused by the freeze-thaw cycle in the field environment,revealing the development of temperature,water content,pore water pressure,and frost heaving force in the radial direction and the displacement change in the vertical direction during this process,so as to verify the feasibility of freeze-thaw cycles for the treatment of soft clay ground.The test results show that the permeability coefficient of soft clay will increase with the increase of the number of freeze-thaw cycles.After 15 freeze-thaw cycles,the permeability coefficient will increase by 3-4 times;after the freeze-thaw cycle,the large pores in the soil will increase,the soil particles become broken and the overall structure becomes more loose;the compression deformation of the soft clay increases after the freeze-thaw cycle,and the pore water pressure change is greatly affected by the initial dry density of the soil sample;The modle test soil sample undergoes freezing and thawing cycle,there will be obvious smelting steps and a lot of free water will be produced.During the freezing process,a large negative pore water pressure will be generated in the soil,the water will migrate to the frozen area,and the water content in the unfrozen area will decrease.The soil samples have frost heace and melting during the freeze-thaw cycle and generate radial earth pressure.The above test results prove that the freeze-thaw cycle greatly promotes the drainage and consolidation process of saturated soft clay,so the application of freeze-thaw cycle in the treatment of soft clay foundation is feasible,but the specific technology and the combination with other methods need further research.