| Loess was formed in the Quaternary of geological age,through wind transport and deposition.It has obvious structure,large voids in soil,complex material composition,and high water sensitivity.Loess presents typical engineering properties.Loess is very sensitive to water content due to its strong water sensitivity and structure.Compressive deformation of soils includes three parts:instantaneous deformation,consolidation deformation and creep,among which consolidation deformation is the largest.Under the traditional framework of soil mechanics,the constitutive relationship of soil is basically confined to stress and strain,relation with the time factor is not taken into account.This is quite different from the actual engineering.Extensive experiments and engineering practice show that the rheological properties of soil play an important role in many engineering failures and can not be neglected in its deformation research.Gibson foundation is the most common form of foundation in engineering practice.Its shear modulus increases linearly with depth.Traditional consolidation theory of soil mainly adopts homogeneous soil foundation model,while the research on the characteristics of heterogeneous Gibson foundation along depth is rarely examined.The following work are carried out in this study.1.A large number of geological data and field research,the genesis and distribution characteristics of loess are reviewed.The physical and mechanical properties of loess in Taiyuan area are summarized through laboratory experiments.The existing soil consolidation and creep studies are summarized.The shortcomings and limitations of the existing research work are analyzed.2.Taking the original loess samples from a construction site along Fenhe River in Taiyuan area as raw materials,the remolded loess samples with different water content were prepared under the same compaction work according to the geotechnical test standard.Then the K0 consolidation tests were carried out on the original loess samples and the remolded loess samples with different water content by using Nanjing WG single lever consolidation instrument,and the loading was applied by Chen Zongji graded loading method.From experimental data,the consolidation characteristics of remolded loess with different water content are analyzed.By comparing the consolidation test results of remolded loess with that of undisturbed loess,the influence of structural properties on the consolidation deformation of loess is discussed.3.By using the empirical method,the strain-time curve obtained from the consolidation test of unsaturated remolded loess is originally fitted,and the fitting degree of different empirical functions is compared,and the fitting parameters are analyzed.The rheological model is established by using the combination of classical rheological elements,and the parameters of the model are obtained by fitting the constitutive equation of the rheological model.The effects of water content and applied stress on the parameters of each model are analyzed.4.From the classical Biot consolidation equation,the two-dimensional consolidation equation of Gibson saturated foundation is obtained by thin-layer method.The consolidation equation of Gibson saturated foundation is obtained by weighted residual method in finite element analysis.Then the boundary condition of foundation is introduced to solve the consolidation equation,and the influence of shear modulus variation coefficient on the consolidation characteristicsoftwo-dimensionalsaturatedfoundationisanalyzed emphatically. |
