Calculation Thoery And Its Engineering Application Of Settlement Of High-filled Embankment Based On Elasto-viscoplastic Constitutive Model

Due to the rapid development of high speed expressway and railway in central or western where hills and mountains are widely distributed,the high embankments appear more frequently in our country.Therefore,effective calculation and prediction of settlement deformation during construction and post-construction always be a crucial project of road building.Under the combined influence of low confining pressure of embankment and high stress in embankment body,the settlements problem will be more complicated because of the over-consolidation,dilatancy,strain-softening and so on.Based on the time-dependent 3D elastic viscoplastic constitutive model,which can reflect the rheological behavior of the over-consolidated soil,the main research performed in this study are concluded as follows:(1)The subloading Cam-clay model proposed by Hashiguchi is improved by using evolution function with over-consolidation state parameters,which is based on Hvorsley Plane.Regarding the improved subloading plane as the reference yield plane,and according to the Relative over-stress theory,the new elastic viscoplastic constitutive model is established,which can reflect the dilatancy,strain-softening,stress history and character of time-dependent for over-consolidated soil.The over-consolidation state parameters of new model can obtained by triaxial shear tests,and comparing with the matching method of Nakai model and Asaoka model,the physical meaning is more certain.Finally,by introducing two over-stress parameters(over stress parameter m' and time-dependent parameter co),which can measured by triaxial compaction tests whose strain velocities are different.The method of measuring m'and c0is given combing the triaxial test data of France embankment soil and Hong Kong marine over-consolidated soil.(2)Through the User-material Subprogram UMAT Portal in ABAQUS,the stress integration algorithm of elastic viscoplastic constitutive model is performed by program.Taking the viscoplastic deviator strain increment as iteration variable,the dynamic yield function is solved by using the Newton downhill method.Finally,reliability of the algorithm of the proposed elasto-viscoplastic constitutive model is verified by the triaxial test data of France embankment soil and Japan Fujinomori over-consolidated soil.(3)Combining the indoor triaxial test data of compacted soil,by using the total stress approach and ignoring the effect of matric suction,the model proposed in this study correctly reflects the characters of dilatancy,strain-softening and time-dependent,and the predicted result is matched well with the experimental data.(4)Based on the high embankment engineering in Intelligence Drive part(K1+430-K1+620)in Xiang River District in Changsha Hunan.Combing the geological survey data and mechanics parameters of soil,the material parameters in the model are ascertained.By using the model proposed in this study and element birth-death method in ABAQUS,the layered filling process of the high embankment is simulated accurately.The analysis shows that compared with Mohr-Column model,the prediction results of new model are more similar with monitor settlements.The predicted post-construction settlement will be about 7.9cm after 10 years,which satisfy the control standard of post-construction totally.