Research On Mechanical Property And Constitutive Mode Of Coarse-Grained Soils

Coarse-grained soil has many good engineering properties, and its applications become increasingly widespread. In order to adapt to the analysis of the civil construction’s structural strength and deformation, the research of coarse-grained soil has become an important topic in the academic session. In the meantime, the practicality and rationality of the constitutive model that coarse-grained soil adopts largely determines the quality of the geotechnical engineering numerical analysis. There is no widely recognized constitutive model today, which can be used for all coarse-grained soil. For the above reasons, study and discussion are unfolded in this paper。(1) Large consolidated drained triaxial compression test was done to study the hydrokinetic characteristic of the coarse-grained soil with different coarse material contents and with different compaction degree. From the test results, we can get the following conclusions:Shear strength increases rapidly with the growth of the coarse material when the coarse material is in the range of30%and50%. With the coarse material growth, the samples have a tendency towards strain softening, and the dilatancy effect gradually increases. The lower the confining pressure is, the more obvious the dilatancy effect is. when compaction degree of coarse-grained soil is greater than93%, compaction degree has little effect on soil strength and soil strength is mainly determined by the surrounding pressure. With the increase of the compaction degree, the soil deformation is significantly reduced, so we should increase the soil compaction degree as much as possible.(2) The applicability abilities of Duncan-chang model and Rowe shear-swelling model are discussed. Duncan-chang model can’t reflect soil’s deformation well. In this paper, a parabolic relationship through the origin of axial strain square and lateral strain is is developed, and form which the improved Duncan-chang model is deduced.(3) The verification of the improved model is performed abased on the test data and the data in the document [9]. The verification result indicates that the improved model can reflect the coarse-grained soil volumetric behavior well, and the model can dovetail nicely to the properties that the dilatancy is more likely to occur at the lower confining pressure and the tangential poisson ratio tend to be equal.(4) The improved model’s parameter L is discussed, from which we can discovered that L=4can be used as the criterion for dilatancy. The dilatancy phenomenon can’t occur when L≥4; when L<4, the dilatancy phenomenon will occur at a lower confining pressure, and the lower the L is, the more easy the dilatancy phenomenon will occur, the lower critical confining pressure of the dilatancy and shear dilatation is, the small the cumulative axial strain at the same confining pressure is.