Dilatancy Of Soil Mechanism And Experimental Study

The development of geotechnical engineering is inseparable from the understanding of the nature of the soil. Soil deformation and strength penetrate through the whole process of geotechnical theory development. Soil constitutive model as the foundation of geotechnical engineering theory system, provide the theory basis for the development of engineering. Since1963the Cambridge model has been put forward, the soil constitutive theory as the basic question of theory and practice in geotechnical engineering has been the subject which geotechnical workers focus on. The two basic problems in the soil research are soil deformation and stability.The basic soil characteristic is the dilatancy and the stress hardening. They are a pair of mutual coupling nature. At present the studies on stress hardening is quite successful. But the dilatancy process is much more complex and influenced by numerous factors, the research of dilatancy is still not perfect. In order to properly describe the dilatancy,a lot of work need to be done.This paper mainly draws the following results:1、The model with phase change state replace critical state as the reference state of dilatancy sand, can reflect the transition from cut shrinkage to dilatancy. It can reflect two process of soil changes:shear shrinkage and dilatancy.2、This paper makes a brief summary of soil constitutive model development and the dilatancy mechanism. This paper introduced the conception of phase change and state parameter,corrected the hardening parameter to build a constitutive model for dilatancy of sand related to the state of materials.3、In this article, constitutive model is validated through a large number of consolidated undrained (CU) triaxial test and consolidation drainage (CD) triaxial test. The simulation results of theoretical mode and the experimental results are in good conformity. So the proposed model has better applicability.4、Loose sand under the action of the shear stress only shrinkage, however middle dense middle dense sand firstly shrinkage and then dilatancy. And more dense the dilatancy more obvious.5、With the increase of confining pressure, when the sample achieve to maximum shear stress, the corresponding axial strain increase. That means, the confining pressure greater, the shear capacity increase. Along with the increase of confining pressure, the differences of shear capacity became smaller. Or rather, the greater the confining pressure, the influence for shear ability of sample which different initial void ratio, is not obvious. In addition, the sample show softening phenomenon in the low confining pressure. And the greater the initial porosity ratio (the more loose sand),the peaks appeared the earlier.