| Land reclamation has become an important method for port dredging and dredged slurry treatment and land development in coastal countries.The dredged slurry after dredging must undergo vacuum preloading treatment before construction can be carried out.Based on the study of the basic characteristics of dredged slurry and the characteristics of vacuum preloading consolidation,this paper aims to explore the clogging mechanism of vacuum consolidation and establish the theory of vacuum consolidation.The consolidation theory of dredged slurry was studied to obtain a vacuum consolidation solution with better engineering application value,and to provide theoretical calculations for the vacuum consolidation of soft soil foundations.Based on the improved consolidation equipment and the measurement method of permeability coefficient,the consolidation test and permeability test of dredged slurry with different initial moisture content were completed.Based on the analysis of the compression and permeability characteristics of dredged slurry in low stress stage,a formula was proposed to express the relationship between void ratio,effective stress and permeability coefficient of dredged slurry with high water content in semi logarithmic coordinates by segments,and the applicability of the formula in different initial states was given.A series of vacuum preloading laboratory tests were carried out to monitor the transmission and distribution of vacuum in drainage body and soil in real time,which provided a scientific basis for the proposal of vacuum transmission formula.The clogging mechanism of vacuum consolidation was revealed.The judgment standard of clogging formation and the method of dividing clogging area were given,and the formulas of clogging coefficient and clogging ratio with time,space and vacuum degree were put forward.Through the research and analysis of the settlement displacement of the soil at different positions,the consolidation effect of the dredged slurry under the action of different vacuum preloading was obtained.Based on the research on the engineering characteristics and consolidation characteristics of the vacuum preloading method for the treatment of dredged slurry,a theoretical model of large deformation radial consolidation considering the clogging effect was established.The model was taken into account the influence of the clogging coefficient during the consolidation process,as well as the nonlinear changes in soil compression and permeability.The analytical solution for the consolidation of the dredged slurry treated by vacuum preloading was obtained by derivation,and the explicit solution was given by the optimized value method,and the correctness of the solution result was verified by comparison with the existing solution.A vacuum degree transfer formula considering factors such as timeliness,limit depth and nonlinear attenuation was proposed,and a vacuum consolidation solution considering the influence of vacuum degree transfer was derived.Based on the development formula of clogging coefficient and clogging ratio with time,space and vacuum degree proposed in this paper,the vacuum consolidation solution considering the development of clogging was derived.It was revealed that the soil that was closer to the PVD under vacuum consolidation was consolidated first,and the clogging zone was basically no longer consolidated after the formation of clogging,and a vacuum consolidation model considering non-uniform strain was established.Combining the segmented expression formula of the relationship between the void ratio of the high water content dredger sludge and the effective stress and permeability coefficient,the vacuum consolidation solution considering the consolidation characteristics of the non-uniform strain and high water content dredger sludge was obtained. |
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