Elastic-Viscoplastic Consolidation Theory Of Non-linear Rheologic Structured Soft Clay And Settlement Calculation Of Vertical Drains Ground

Soft clay of marine sediment extensively distribute near the littoral in southeast China. Rheological & structured properties which are important research task of geotechnical field have important effect on soft clay consolidation resulting in mainly difficulties in design & construction of groundwork. As a subtopic of the project of National Natural Science Foundation deal "study on groundwork design theory and method of finishing settlement", the research work was supported by National Natural Science Foundation of China(50279021).The major contents are mainly summarized as follows.(1) Clarify the important meanings of researching non-linear rheologic and structural properties of soft clay. Research constitutive models of rheologic and structured soft clay from theory and test and numerical simulation aspect.(2) Improve Yin & Graham timelines model by bringing forward the change of reference stress(initial stress) along the different depth.lmproved model include load.penetrability and the change of reference stress(initial stress) along the different depth. Establish a one-dimensional non-linear rheologic consolidation equation by using improved model. Based on the principle of iterative and general analytical solution for one-dimensional consolidation of layered soils, solution of semi-analyticaly method has been developed herein for elastic-viscoplasty consolidation problem of layered ground. Derivate formulae of average consolidation degree and some time settlement and general settlement of groundwork has been established.(3) Establish a new one-dimensional elastic-viscoplastic consolidation model of non-linear rheologic and structured soft clay by introducing structured yield stress for analyzing stress-strain and logical hypotheses and time dependence relationship based on Yin & Graham time lines model. The methods of semi-analytical and finite difference of new model are introduced. The new model includes stress-strain time dependence and structured yield stress augment bringing by viscous deformation and the effect of strain rate of structured yield stress. Compare the new model with Yin & Graham model and soft-soil-creep model of PLAXIS and test results of Lerouiel et al. & Imai et al. to validate its correctness and to expatiate that rheologic and structured properties effect on soft clay consolidation.(4) New model calculation needs eight fundamental parameters, such as original void ratio, permeability coefficient, re-compression coefficient, compression coefficient, coefficient of secondary consolidation .original effective stress .structured yield stress and strain rate (while the effective stress equal to the structured yield stress).(5) Analyze ground dissipation of pore pressure and settlement and consolidation degree affected by various factors change such as soil structure, structural strength, re-compression index, coefficient of secondary compression, the magnitude of loading, permeability coefficient, the rate of loading, the thickness of clay and the self -weight stress etc.(6) Obtain three phase compression curve of structured soft clay basing on test results of Schertmann and Nagaraj: elastic compression stage, structure damage suddenly dropping stage and normal compression stage. Reasonable structured yield stress and compress parameter could be founded by the new curve. Bring forward calculation methods of consolidation degree and settlement and additional settlement of vertical drains ground affected by disturbance and structure properties.(7) Adopt new model and disturbed structured soil calculation formulae making numerical simulation for prefabricated plastic drains preloading of soft soil ground of Shenzhen-Hongkong west route-way to verify the availability and practicability of the new model and to clarify that structured disturbance and viscous effect have great significance on soft clay consolidation analyses.