预压作用下软土微观结构试验及弹黏塑性模型研究

Study of elasto-viscoplastic model and microstructural test of soft soils under consolidation by preloading method

为了揭示软土固结蠕变机制,计算软基"工后沉降",开展了室内模拟真空、堆载以及真空-堆载联合预压加固软土的固结蠕变三轴试验及三轴试验前、后的微观结构试验。建立了能考虑微观结构改变的弹黏塑性(EVP)软土蠕变模型。研究结果表明:原状软土样在真空预压、堆载预压、联合预压3种预压荷载作用下,固结过程和蠕变过程具有耦合效应;土体微观结构参数的改变与宏观工程性质的改变具有相辅相成的关系;EVP模型弱化了具体应力路径的变化,其反映弹性的参数和反映黏塑性的参数可由微观结构参数确定;改进的EVP模型既能计算土体的弹黏塑性变形,也考虑了土体微观结构的变化,能更全面地反映土变形的实质。

In order to reveal the mechanism of consolidation-creep of soft soil, the settlements of soft foundtions after the completion of projects are calculated. The triaxial consolidation and creep tests have been carried out which simulate of soft soils under consolidation by vacuum, surcharge, and combined vacuum-surcharge preloading. The microstructure tests of soft soils before and after triaxial tests have been carried out also. The elasto-viscoplastic (EVP) model which could consider the change of microstructure of soft soils is set up. The outcome is drawn as follows:The results of triaxial tests show that the course of consolidation and the course of creep of samples under the loading of three different preloading methods have the coupling effect. The results of microstructure tests show there are relationships of supplement each other between the change of microstructure and the change of engineering characters of soft soils. The specific stress path of change is weakened in EVP model, in which parameter reflected the elastic and parameter reflected the plasticity and viscosity of soft soils could be determined by the microstructure parameters. The improved EVP model not only can calculate the EVP deformation of soft soils but also considered the microstructure changes of soft soil, which can better reflect the essence of soil deformation.