Research On The Normalized Properties Of Loess Based On Structural Parameters

In recent years,various loess disasters such as landslides,mudslides,and collapses have occurred frequently in the Loess Plateau,posing a huge threat to human life and property.Loess has large pores,and its strength is easily weakened under the action of water,softening deformation occurs,and the deformation accumulates and gradually penetrates to cause loess disasters.As a bearing body of geological disasters,Malan loess with a shallow burial depth needs urgent research on its mechanical deformation characteristics.In this paper,Yan'an Nangou,located in the hinterland of the Loess Plateau,is selected as the research area,and the normalized properties of compression and shear stress-strain of Malan loess in this area are explored through field survey sampling,laboratory experiments and theoretical analysis calculations.The normalized behavior focuses on the quantitative estimation of stress-strain and strength of a certain type of soil.This paper uses two types of structural mechanical parameters to compare and analyze the normalization of confined compression and triaxial shear stressstrain,and finally provides a new idea for studying the normalized behavior of loess and other strong structural or over-consolidated soils.The main conclusions of this paper are as follows:(1)The structural yield stress of undisturbed and remolded loess is negatively correlated with moisture content.Both structural yield stress and void ratio structural parameters can normalize the confined compression deformation of loess.Based on the two parameters,the normalized behavior of undisturbed loess compressive strain is discussed,and the normalized equations are established respectively.Among them,the void ratio structural parameter is more remarkable for the normalization of compressive strain of loess.(2)The stress-strain relationship of the undisturbed Q3 loess changes from a weak hardening type to a strong hardening type with the confining pressure increasing,but it will show certain softening characteristics under conditions of extremely low water content and extremely low confining pressure.Except for extremely low water content and low confining pressure,the stress-strain relationship of remolded loess under different water content and different confining pressure basically shows strain hardening.The cohesion of Q3 loess decreases as a logarithmic function with the increase of water content,while the internal friction angle is basically stable within a small range of 21°?23°.The cohesion,structural strength,and structural yield stress of undisturbed loess decreased in the form of logarithmic,exponential,and power functions with the increase of water content.Under the same moisture content,the yield stress of the structure is always the largest among the three,the structural strength is the second,and the cohesion is the smallest.(3)Q3 loess with moisture content of 5%and 10.2%does not have normalized properties under confining pressure below 400kPa,and loess with moisture content of 17%has normalized properties under confining pressure above 300kPa,and loess with water content of 22%,27%and 32%has significant normalized properties under confining pressure above 200kPa.Taking the initial tangent modulus or ultimate deviator stress as the normalization factor of the undisturbed Q3 loess,the normalization equation of the loess in a fixed mathematical format is constructed:?1-?3=f(?3)·?1/m+k·?1,the stress-strain of the undisturbed Q3 loess with different moisture content is established by applying this equation.The normalized equation of strain relationship,the stress-strain fitting model has high accuracy.(4)Based on the stress structural parameters,a fixed format stress-strain mathematical relationship of the undisturbed loess is constructed:(?1-?3)y=f(?3)·?1/m+k??1·m?,the normalized equation for the structural stress-strain of the loess within the full water content and full confining pressure range is established,and the normalized equation is used to predict the undisturbed loess stress and strain,the prediction results are relatively accurate except for a few abnormal confining pressure points.(5)The structural properties of loess are extremely obstructive to the normalization of loess.The normalization equation of loess is closely related to structural mechanical parameters.Compared with the boundary state loess structural mechanical parameters,the whole process of dynamic quantification of loess structural mechanical parameters is used to normalize the loess,which has a stronger normalization.The comprehensive structural potential that dynamically quantifies the structural changes of loess during the whole process is dimensionless,can reflect the release process of the loess structure,has a good normalization effect,and is universal for different stress paths such as compression deformation and shear deformation.