Research On The Constitutive Relation Of Coarse-grained Soils And Their Applications In Excavation Engineering

Shenyang is located in the alluvial-proluvial plain by the River Liao and the River Hun.The major area of the city is composed of the medium-coarse sand,the gravelly sand and the round grain sand.Hence,it has great practical significance to research the physical and mechanical properties of the coarse-grained soils in Shenyang area.Concerning the issue,moisture contents,densities,proportions of solid particles and relative densities of the three kinds of soil samples which were taken on the site are obtained by a serious of indoor soil tests.Also,the large scale triaxial consolidation drained shear tests are processed by groups with different relative densities.The date of the consolidated drained triaxial shear test shows the initial modulus and the peak strength are greatly influenced by the relative density for the medium-coarse sand,the gravelly sand and the round grain sand.Through curve fitting,the empirical formula of coefficient M for the initial modulus and coefficient K for the peak strength is established.Then,based on the theory of Disturbed State Concept,the general disturbance function which can consider the influence of both the advantage disturbance and the disadvantage disturbance is established in which D,is used as a parameter of disturbance.Combined the results of triaxial tests,the non-linear plastic constitutive models focused on the three kinds of soils are obtained in which the disturbance function is introduced of the traditional Duncan-Chang model.Also,the calculation curves by the modified model are analyzed comparing the test curves.On the basis of these,the modified models of the three kinds of soils considering the influence of disturbance are processed by the FEM program ABAQUS.And the user-defined UMAT subroutines are obtained.At last,the excavation of Caozhong Station in Shenyang Metro Line 9 and the excavation of a residential in Shenyang are taken as engineering projects to analyze the horizontal displacements of retaining piles and the ground settlements near the excavation in different construction processes.The test curves show that it is better to use the modified model considering the influence of disturbance comparing the traditional models.And,fouced on the problem of deformation of excavation engineering,the FEM results show that comparing the analysis of M-C model and Lizheng Deep Foundation program,it has evident advantages to use the modified model in this paper to calculate the deformation nearby in practical matters during excavation as it has a good fitting of the monitoring value.