Consolidation Model for Soft Soil Subgrade Considering the Threshold Hydraulic Gradient and Variable Permeable Boundary
Research purposes:The problem of roadbed settlement is the main cause of engineering accidents in infrastructure such as railways and highways.In order to improve the settlement prediction level of roadbed soil in soft soil areas,considering the non-Darcian flow of soil,the variable drainage boundary,and the nonlinear deformation characteristics,this paper proposes the corresponding piecewise-linear consolidation model.Among them,the seepage model with the threshold hydraulic gradient is used to reflect the effect of non-Darcian flow,the continuous drainage boundary is used to describe the changes in the permeability performance of soil boundaries,and the relationship of e-lg(av0)is used to represent the nonlinear deformation characteristics of soil.Then,some examples are used to analyze the change of boundary permeability,nonlinear deformation of soil and consolidation behavior of soil under non-Darcian effect,in order to provide theoretical support for the prediction of settlement after construction of soft soil roadbed.Research conclusions:(1)The stronger the non-Darcian effect of soil(i.e.the larger the value of the threshold hydraulic gradient),the worse the boundary permeability(i.e.the smaller the interface parameter),and the more obvious the phenomenon of consolidation hysteresis at the same time.(2)The value of the threshold hydraulic gradient can simultaneously affect the consolidation process and the final result.(3)The initial compression coefficient considering the threshold hydraulic gradient and the continuous drainage boundary has a significant impact on the settlement process.(4)The proposed consolidation model can simulate the settlement process of deep soft soil subgrade,and the relevant conclusions can be applied to the process of pile loading drainage reinforcement of deep soft soil.
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