软土蠕变-固结特性及计算模型研究

根据国内外研究动态和实际工程的迫切需求，对软土蠕变—固结特性、计算模型、模型的数值求解方法和工程应用等进行了系统的研究，探讨了土工应力—应变模型、流变模型和固结模型的耦合机理，建立了实用的非线性弹粘性固结模型。研究表明，软土在任一时刻的变形都可以分解为瞬时变形和蠕变变形，其中，瞬时变形也呈现比较明显的非线性特征；土体变形的时效性由固结特性和粘滞特性共同决定，应力水平低时以固结变形为主，反之，土体的变形主要来源于剪切蠕变；土体的蠕变变形与孔隙水压力的消散有关，在同样的条件下，土体渗透性越差，蠕变变形越大；对于有厚度的土层，土体的次固结是在主固结过程中同时发生：土的蠕变对应力和应变的影响程度取决于土体的排水条件，当地基排水不良时，应力水平将随时间增高，变形计算中若不考虑蠕变特性将可能忽略地基潜在的失稳趋势。所以，考虑蠕变特性不仅是对计算结果的修正，而且是对工程安全性的重新评价。通过对有代表性的实例的计算和分析，验证了计算模型的合理性和结论的正确性。

RESEARCH ON CREEP-CONSOLIDATION CHARACTERISTICS AND CALCULATING MODEL OF SOFT SOIL

Based on the research trends of soil rheology and the stringent demand of practical engineering, the characteristics of creep-consolidation in soft soil, computational model, homologous numerical method and its application in engineering are systematically studied. The coupling of stress-strain model for soil and rheology model as well as consolidation model is researched. The practical model of nonlinear elasto-viscous consolidation is established. The study results show that the total displacement of soft soil, at given time, can be divided in instantaneous part and creep part. The instantaneous strain also presents obvious nonlinear property, and the time-dependent behavior of soil deformation is depended on its consolidation and viscosity. When stress level is lower, the displacement results mostly from consolidation. Otherwise the displacement primarily originates from shear creep. The creep deformation of soil is related to pore-pressure dissipation. Under uniform conditions, the worse the permeability is, the larger the creep deformation is. For soft soil strata, the secondary consolidation occurs during the primary consolidation, and the influence of creep on stress and strain is decided by drainage condition of soft foundation. The stress level will rise with time when drainage condition is bad. The possible destroy may be missed, if the characteristics of creep are not be taken into account of calculation. So, for the security of an engineering, the creep considered not only corrects the calculation results, but also is an afresh evaluation. Through the calculation of a representative example, the rationality of creep-consolidation model and the validity of conclusions have been tested and verified.