Research On Soil Structural Parameters And Structural Constitutive Model Of Unsaturated Loess

Because of its special mechanical and engineering characteristics, loess has been the one of the important study points in geo-engineering. The fundamental research basis of these properties in soil mechanics is the structural characteristics of the loess. The key in studying the structural characteristic is the soil structure quantification description. Based on the observation and analysis of a large number of new developments in loess soil mechanics, unsaturated soil mechanics and loess dynamics, the paper takes the soil structural parameters and the relationship between soil structure and mechanical properties of unsaturated loess as its essential research duties. The main achievements of the paper are as follows:1. On the basis of systematic analysis and recognition to trhe thoughts of soil structure potential, it is found that the current structure parameters have their limitations that can not reflect the variations of soil structure both in initial natural soil state and in isotropic compressive conditions. So researches have been made to improve it, and put forward two new parameters, one of which can reflect the effect of the isotropic compressive conditions on the soil structure, the other can reflect the initial structure physical state, which can be obtained by tests combining the thoughts of releasing structure potential with the principle of cone penetrometer for liquid limiet test.2. By large amount of tests, the rationality and sensitivity of the two new parameters in descripting the variations of soil structure have been demonstrated. And furthermore, the continuity and consistency in using them together with the previous parameters to quantatativelly describing the soil structure variation through the whole process from the initial state, to the isotropic consolidation stress state and then to the triaxial shearing state are approved. Finally, the above concepts are also extended to the dynamic condition to describe the structure variation with the progress of dynamic stress or strain. This further demonstrates the rationality of the thoughts of soil structure potential. 3. The curves of soil structure variation in different soil, different stress states and different stress patterns have been quantified. The approach, form and merits of describing them by using hyperbolic curves are discussed. Then the structural constitutive model of intact unsaturated loess both in static and in dynamic stress conditions are established. The results calculated by using the models are in accordance with that of tests.