Study On Unsaturated Dynamic Constitutive Model Under Cyclic Loading For Chuanxi Talus Mixed Soil

The foundation settlement issues of subways, highways and railroads in the process of operation become increasingly prominent and studying dynamic mechanism of soils under traffic loading and how to establish the dynamic constitutive model which has become a major technical problem to be solved. Existing research objects are in the sand and soft clay, talus mixed soil with little research. In a complex geological environment of the mountains of the Western Sichuan exist widely a kind of talus mixed soil, with many origins, various compositions, multiple gradations, and complex particle morphology and environment sensitivity. Experimental studies have shown that unsaturated nature and content between the fine particles are two features for talus mixed soil in western Sichuan. Therefore, the study has the important theoretical and engineering applicable value. Because it researches the dynamic characteristics of the mixed soil under traffic loading in consideration of the two basic features of unsaturated nature and content between the fine particles, in order to construct the unsaturated dynamic constitutive model for such soil under dynamic response analysis and provide a reliable theoretical basis and analytical methods for dynamic stability analysis and disaster prevention concerning mixed soil structures, the natural slopes, high embankments, highways and railway subgrades composed of the mixed soil in western Sichuan mountainous area and even the entire southwest regionAfter a series of studies by laboratory experiments, two kinds of mixed soils differ in clay content and clay mineral soil. According to the microscopic theory of soil mechanics, natural void ratio will be a difference. The shear strength of soil sample 2 is greater than that of soil sample 1 during unsaturated static triaxial test. It uses the parameter of ks to reflect the impact of test curve in this article, according to the microscopic theory of soil mechanics. Hydraulic coupling relationship of unsaturated soils can be built by Van Genuchten SWCC. It use the parameters of βSr、 n、m to reflect the impact of test curve. Unsaturated static triaxial test showed that the stress-strain behavior of two soil samples is affected more by moisture (matric suction). It uses the parameters of ks、s to reflect the stress-strain behavior. Unsaturated consolidation test showed that the matrix suction is an important parameter affecting mixed soil consolidation characteristics. It uses the parameters of X(s)、κ、 r、β to reflect the consolidation characteristics. So, there are 10 parameters associated with unsaturated nature and content between the fine particles. They are e、βSr、n、m、ks、s、κ(s)、κ、 r、β. These parameters can be gained through laboratory experiment results or test curve fitting.Within the framework of the elastic-plastic bounding surface model, combined with the real description of unsaturated soil collapsible performance LC yield curve, based on the mapping rule of mobile mapping origin, considering the two main features of talus mixed soil and taking classic MCCM as plastic potential equation, a dynamic constitutive model for unsaturated mixed soil has been elaborated. Comparisons between experimental results and model simulations show that the elaborated model is not only capable of describing the unsaturated loess behaviors under Static loading and cyclic loading, but also can truly predict the phenomenon of hysteretic properties during both loading and unloading. The model parameters can be obtained through fitting or routine experimentation results.