Unified Description Of Structural Parameters And Constitutive Relationship Of Loess Based On Comprehensive Structural Potential

Natural loess has remarkable structure.As an important index of loess,its structure,together with other physical indexes of loess,affects the mechanical properties of loess itself.During the process from the beginning of the stress to the failure of loess,the strength of the soil itself is not enough to resist the external force.The research on the relationship between the structural evolution law and the strength deformation is very important,and the loess engineering disasters caused by the structural evolution are numerous.The research on the structure of loess is of great significance for the current lar-ge-scale infrastructure construction.Based on the comprehensive structural potential theory,this paper looks for the common evolution rules and characteristics of various structural parameters which are also evolved due to the comprehensive structural potential,constructs the mathematical expression of structural parameters and normalizes the structural parameters.On the basis of Duncan Chang hyperbolic model theory and considering the structure of loess,a new constitutive relation based on normalized structural parameters is proposed.The main research results are:(1)Based on the results of the conventional confining compression test and the confining compression test under suction balance,when the water content is large,the soil strength is large and there is almost no difference between,the two types of test results.With the decrease of the initial water content,the actual water content in the conventional confining compression test is slightly larger than the initial water content.At this time,the soil strength and structure are slightly smaller.The evolution law of strain structural parameters is drawn based on the confining compression test,The influence of matrix suction and particle bonding on soil structure is analyzed,and the rationality of the comprehensive structural potential theory is demonstrated and verified.(2)Through the conventional triaxial test,under the control of the consolidation confining pressure and water content,the soil with three different structural states of undisturbed,remolded and saturated are tested respectively,and the corresponding stress-strain curves are drawn,the evolution laws and internal relations of different structural parameters are analyzed,the stress coefficient K is highlighted,and the different stress parameters are connected with this parameter,and the mathematical models of various stress structural parameters are proposed,The internal relations of various structural parameters are concretely displayed.(3)The essence of soil structure change is that secondary structure will be generated after the primary structure is destroyed.As a special property of loess structure,the structural potential released by the same soil in different experiments should be the same.Normalization of structural parameters is to eliminate the impact of different stress paths and consolidation confining pressure on the initial structure of soil,All kinds of parameters are normalized and their corresponding change curves are drawn.Their evolution laws are consistent,which proves that all kinds of structural parameters are essentially the same in the expression of soil structural damage.(4)Based on Duncan Chang hyperbolic model theory,considering the structural influence of loess itself,the normalized structural parameters are integrated into Duncan Chang expression,and a new loess constitutive relationship is proposed.Using this constitutive relationship,three typical loess samples from different lands are calculated and analyzed,five important parameters of Duncan Chang model are obtained,and the commonness of K and N coefficients of loess in this constitutive relationship is boldly guessed and further discussed.