Cement-clay Improvement Of Aeolian Sand In Seasonally Frozen Areas Research On Mech Anical Properties

With the continuous development of China’s road engineering,the requirements for the structural strength and stability of the roadbed are getting higher and higher,especially the physical and mechanical properties of the roadbed filler itself in the seasonal permafrost zone are more stringent,but in the construction of road engineering in Shuangliao area of Jilin Province,due to the long-term accumulation of wind-deposited sand,there is a lack of excellent roadbed filler materials around,and only abundant wind-deposited sand resources,but wind-deposited sand cannot meet the requirements of roadbed filler,which brings great difficulties and challenges to the road construction,so the improvement of wind-deposited sand is of great significance to the local road traffic construction,improving the ecological environment and promoting regional economic development.This article improves aeolian sand by adding cement and clay,and conducts particle analysis tests,specific gravity tests,boundary moisture content tests,and compaction tests to study the basic physical properties of cement-clay improved aeolian sand.Through static triaxial tests,the mechanical indicators such as cohesion and internal friction angle of cement-clay improved aeolian sand are studied.Through permeability tests The dynamic triaxial test and SEM electron microscope scanning test were conducted to study the impermeability,dynamic characteristics,and microstructure characteristics of cement-clay modified aeolian sand.The following conclusions were drawn:(1)With the incorporation of cement and clay,the maximum dry density,liquid limit,plastic limit and plasticity index of the soil were all greater than those of the pre-amended anemophilous sand,and showed an increasing trend with the increase of cement incorporation,and the optimum moisture content was slightly reduced.(2)The shear peak strength,cohesive force,internal friction angle,and sh ear strength of cement-clay improved aeolian sand increase with the increase of cement content and confining pressure,but gradually decrease with the increas e of freeze-thaw cycles,and the permeability coefficient increases accordingly.The permeability coefficient,expansion rate,and water absorption decrease with the increase of cement content,while the CBR value increases with the incre ase of cement content.The optimal dosage of cement clay for improving wind blown sand is 5% cement+10% clay.(3)The plastic deformation of improved aeolian sand with 5% cement and 10%clay is smaller than that of unmodified aeolian sand.The dynamic elastic modulus shows an increasing trend with the increase of confining pressure,and the plastic deformation decreases with the increase of confining pressure.The dynamic elastic modulus first decreases and then tends to stabilize during the reciprocating load process.As the number of freeze-thaw cycles increases,the dynamic elastic modulus gradually decreases.(4)The average diameter percentage content of particles in 0% cement+0% clay and 5% cement+10% clay improved aeolian sand increases under freeze-thaw cycles,while the content of small particles increases,the content of large particles decreases,the content of small pores decreases,and the content of large pores increases.The shape of particles and pores develops from a long strip to an equiaxed direction,and the orientation of particles and pores gradually weakens under freeze-thaw effects.After improvement,the micro characteristics of the soil become more stable under freeze-thaw effects.(5)By analyzing the correlation between the shear strength indicators and microscopic parameters of wind blown sand before and after improvement,the microscopic parameters with the greatest correlation with their shear strength in dicators under freeze-thaw cycles were determined.The microscopic parameters that mainly affect cohesion,internal friction angle,and shear strength were also determined through autocorrelation analysis.