Study On Loess Damage And Its Influence On Slope Stability Under Freezing And Thawing

Frozen soil is a kind of special soil containing ice crystals after experiencing low temperature environment.According to its length of time,it can be roughly divided into instant frozen soil,seasonal frozen soil and permafrost.China is one of the countries with the widest loess distribution in the world,mostly distributed in northwest and north China,and is in the seasonal frozen soil area.Seasonal frozen soil areas are often affected by freezing and thawing,and there is frost heaving and melting,which greatly affects the construction of loess structures in the area and the stability of above-ground and underground buildings,and the freezing and thawing effect causes the slope to be damaged and its stability and safety.Freezing and thawing is one of the important reasons for the deterioration of the physical and mechanical properties of loess in seasonal frozen soil areas,and will change the mirstructure of the soil.Therefore,it is of great significance to study the strength changes of loess after freezing and thawing.It is of practical significance to study the effect offreezing and thawing on the stability of loess slopeThis paper relies on the undisturbed loess on the southern bank slope of the northwestern ShaanxiFirst,considering the factors of water content and number of freeze-thaw cycles,the physical properties of loess after freezing and thawing were studied.Analyze the changes in density,void ratio and liquid plastic limitSecondly,scanning electron microscopy(SEIM)and nuclear magnetic resonance(NMR)experiments were carried out to study the microstructure characteristics of the soil after freezing and thawing.The SEM images of the obtained soil samples and the nuclear magnetic resonance curve of the soil samples were used to study the microstructure characteristics and pore distribution of the undisturbed loess particles under different water contents and different freeze-thaw cyclesThen,the unconsolidated undrained and consolidated undrained triaxial shear tests were carried out on the loess samples subjected to different freezing and thawing conditions under different water contents.The relationship between freezing and thawing and the physical and mechanical property of undisturbed loess under different confining pressures and water content was studied.The changes and law of stress-strain curve and shear strength index(cohesion and internal friction angle)of slope loess after different freezing and thawing were analyzed.Exploring the interrelationship between the microstructure of loess and its macroscopic characteristics under freezing and thawing.Finally,the above-mentioned changes in the shear strength indicators c and φ are applied to the slope.Using numerical analysis software to simulate the loess slope before and after freezing and thawing,and to explore the effect of freezing and thawing on the stability of loess slope.In this paper,the laboratory experiments,combined with scanning electron microscopy and nuclear magnetic resonance technology,reveal the physical and mechanical properties and microstructure of the loess under the action of freezing and thawing,explore the relationship between the two and study the effect of freezing and thawing on the stability of loess slope.In order to provide a more reliable test and theoretical basis for the construction of slope engineering in seasonal frozen soil areas.