Study On Soil Parameters Based On Rheology

The stress-strain relationship of soil has a significant time response.The phenomenon that deform with time after loading,and delayed recovery process after unloading,showing two different mechanisms of elasticity and viscosity at the same time.Meanwhile,as soil rheology is affected by many factors,its form is complex.At present,there is no unified method and standard to characterize these properties of soil.Rheometry provides a powerful help to study the rheological properties of materials.Based on rheology,the rheological properties of soil materials are deeply studied in this paper.The following research contents are mainly carried out:Firstly,the basic rheological characteristics and behavior of soft soil and clay are studied through steady shear rheological tests,and the practical significance of the platform value of rheological curve is pointed out.The phase transition of soil under shear and the reaction of internal structure are studied.Under shear,the soil undergoes the process of quasi elastic solid-viscoelastic body-quasi viscous fluid.The response law of soft soil and clay under variable shear rate and constant shear rate is studied.The effects of shear rate,moisture content,shear time,soil types and other factors on the rheological properties of soil were studied.Secondly,the viscoelastic properties and behaviors of soft soil and clay are studied through oscillatory shear rheological tests.The response laws of viscoelastic parameters such as complex modulus,elastic modulus,viscous modulus and phase angle to factors such as water content,soil types,shear rate and strain amplitude are studied.Parameters that can reflect the permanent deformation resistance and fatigue deformation resistance of soil are proposed.The obtained parameters can effectively reflect the viscoelastic characteristics of soil.Thirdly,the influence of mineral composition on clay viscoelastic properties is explored from the micro-level perspective.The viscoelastic parameters of three kinds of single clay minerals,namely kaolin,montmorillonite and illite,and their response laws to oscillating strain,oscillating time,water content and other factors are obtained.The mixed simulated clay was studied and the influence of clay mineral composition on clay was analyzed.The rheological behavior of clay is different from that of kaolin and illite.Montmorillonite minerals make a major contribution to the rheological behavior of clay.Then,it is noticed that two kinds of rheological phenomena related to soil,i.e.thixotropy and transformation of stress-strain relationship,are essentially related to viscoelastic properties of soil,and are studied and characterized based on rheology.The difference of viscoelastic modulus can accurately evaluate the thixotropic characteristics of soil.Positive value represents positive thixotropy of soil,negative value represents negative thixotropy of soil,intersecting with coordinate axis,and soil is compound thixotropy.The weak strain overshoot behavior of montmorillonite increases the irreversible deformation of soil and accelerates the change of thixotropy.Shear hardening and shear thinning behavior of soil can be distinguished from the convexity of rheological curve,and the conversion of stress-strain relationship can be easily distinguished from the peak number of viscosity curve.The results show that rheology has a good research effect on the thixotropy of soil and the transformation of stress-strain relationship.Finally,based on the colloid electric double layer theory,the origin and essence of soil viscoelasticity are analyzed.Electric double layer determines a series of physical and chemical properties of soil and is a comprehensive reflection of complex interactions between soil particles.Zeta(ζ)potential can provide a lot of information about the structure and properties of electric double layer.According to ζ potential,the rheological behavior of soil was revealed.In addition,the bonding between particles is not only dominated by ζ potential,but also affected to some extent by the particle size composition of the soil.If the particle size is too small,the particle spacing will be too large and the viscosity modulus will decrease.In this thesis,based on rheology,the rheological characteristics and behaviors of soil are recognized,studied and discussed,which enriches the research results of soil properties,deepens the understanding of inherent characteristics of soil,and provides a powerful reference for theoretical research and practical application.