沉积泥砂非线性大变形固结沉降计算模型

沉积形成的水底黏性泥砂自重固结过程表现出显著非线性大变形固结特征，应采用大变形固结理论进行泥砂沉积固结计算。基于软黏土一维非线性大应变固结理论，应用有效应力、渗透系数与孔隙比间扩展幂次函数固结本构关系，由达西定律、有效应力原理、连续介质方程等建立大变形固结控制方程，根据固结单元孔隙水渗流、单元变形与泥砂沉积层固结沉降耦合关系形成黏性泥砂大变形自重固结数值模型。泥砂自重作为固结荷载，数值模型假定沉积泥砂各向同性且固结沉降应变、孔隙水渗流仅发生于竖直方向，为一维单向沉积固结过程；采用泥砂沉降柱试验确定泥砂非线性扩展幂次函数关系参数。模型应用中，划分竖向固结单元，由沉积泥砂固结本构关系确定各固结单元有效应力及超孔隙水应力，通过超孔隙水应力时间维度上的消散过程及各固结参数间的耦合关系计算泥砂固结沉降。数值模型计算结果表明，沉积黏性泥砂自重固结初期表现为有效应力调整过程，初始有效应力与孔隙比根据固结本构关系匹配调整为扩展幂次函数关系；沉积泥砂应变与应力固结度存在20%左右误差，泥砂固结沉降发展快于超孔隙水应力消散过程，证明沉积泥砂固结沉降变形的发展与超孔隙水应力消散并非同步耦合。计算模型应用于室内沉降柱试验模拟淤积黏性泥砂自重固结沉降预测中，模型输出与试验结果符合良好。

Numerical model for nonlinear large strain consolidation of deposited sediment

Large strain consolidation theory is applied to calculate deposited cohesive sediment weight deposition and consolidation for the significant nonlinear large strain characteristics. Based on soft soil one-dimensional general large strain consolidation theory and the application of quasi-power functional consolidation constitutive relationships between effective stress, permeability and void ratio, nonlinear large strain consolidation governing equation can be built up according to Darcy law, effective stress principle as well as the soil continuous equation. By the coupling relationship of pore water seepage, element deformation and weight consolidation settlement, a full cohesive sediment weight consolidation numerical model is developed for the nonlinear large strain characteristics. With the fact that deposited sediment weight is as the consolidation loading, the new developed model assumes the deposited sediment layer is homogenous, and the consolidation settlement along with the pore water seepage only occurs in vertical direction, and then the sediment consolidation process can be seen as one dimensional weight consolidation. Moreover, nonlinear quasi-power consolidation constitutive relationship parameters are determined by the cohesive sediment settlement column experiment. Consolidation elements are applied to evaluate the effective stress, excessive pore pressure of different depths, and deposited sediment consolidation settlement is determined by the dissipation of excessive pore pressure in time scale. Numerical model performance shows that there is a clear adjustment process for the relationship of deposited layer effective stress and the void ratio according to the quasi-power functional constitutive relationship in the initial stage. An approximate 20% error between stress and strain consolidation degree means that deposited sediment consolidation settlement develops faster than excessive pore pressure dissipation, which also proves the asynchronous coupling relationship of consolidation deformation and excessive pore pressure dissipation in large strain consolidation. According to the numerical model performances in cohesive sediment consolidation with settlement column experiment, the new developed model outputs show a well agreement with the measured one.