循环荷载作用下非饱和土竖井复合地基固结理论研究

发布时间：2018-05-24 00:41

本文选题：非饱和土 + 固结理论　；参考：《青岛理工大学》2013年硕士论文

【摘要】：近年来，随着我国经济建设的快速发展，大量基础建设工程（如高速公路，高速铁路等）在软土地区进行施工建设，而现有设计理论大多是以饱和土的固结理论为基础，而土体通常是由气、液、固组成的三项体；此外，由于我国已经进入高速公路、高速铁路蓬勃发展的新时期，，且规划中和已建成的线路地区不可避免会经过广泛分布有深厚软粘土的地段，如我国东南沿海、长江三角洲一带等，竖井地基作为一种软基加固处理手段被广泛应用。然而，大量研究表明，经过压实的路基土仍然会处于非饱和状态。因此，从非饱和土的角度出发，采用非饱和土的理论与方法，对循环荷载作用下非饱和竖井地基的基本性质进行研究，解路基审计的理论及相关工程技术问题非常有必要。鉴于此，本文基于前人的工作，从Fredlund的非饱和土固结理论出发，建立任意荷载作用下非饱和土竖井复合地基固结计算模型，通过理论推导并结合有限元方法，对任意荷载作用下非饱和土竖井复合地基的固结问题进行了全面的分析研究。首先，在Fredlund非饱和土固结理论方程基础上，联合Darcy定律和Fick定律，建立关于有限深度的非饱和土竖井复合地基在任意荷载作用下固结的微分方程。通过Laplace变换，得到超孔隙气压力和超孔隙水压力在变换域内的半解析解。应用自编程序分析各种循环荷载作用下非饱和土的超孔隙气压力和超孔隙水压力的变化规律。其次，在之前研究的基础上，对计算模型进行修改完善，并运用有限元方法，对考虑涂抹效应的有限深度非饱和土竖井复合地基在任意荷载作用下超孔隙气压力、超孔隙水压力以及土体沉降的变化规律进行了分析研究。最后，对计算模型再进行更进一步改进，运用有限元方法，分析了考虑水平和竖向二向渗流的有限深度非饱和土竖井复合地基在任意荷载作用下超孔隙气压力、超孔隙水压力以及土体平均固结度的变化规律，并给出了此种土体模型在土体固结计算中可以忽略土体竖向渗流情况时的土体H k wz/kwr关系的大致范围。本文基于高速发展的工程建设对现有非饱和土固结理论提出更新、更高要求的客观现状，探索性地研究了任意荷载作用下的非饱和土竖井复合地基的固结沉降规律，给出了各种土体模型中超孔隙气压力、超孔隙水压力在各种荷载作用下的变化规律并分析对比了其之间的异同，对于非饱和土固结理论的完善发展具有重要意义。
[Abstract]:In recent years, with the rapid development of economic construction in our country, a large number of infrastructure projects (such as highway, high-speed railway, etc.) have been constructed in soft soil areas, and most of the existing design theories are based on the consolidation theory of saturated soil. The soil mass is usually composed of gas, liquid and solid. In addition, since China has entered the expressway, the high-speed railway is booming in a new period. And it is inevitable that the planned and completed railway areas will be widely distributed in areas with deep soft clay, such as the southeast coast of China, the Yangtze River Delta and so on. The shaft foundation is widely used as a means of strengthening soft foundation. However, a large number of studies show that the compacted subgrade soil will remain unsaturated. Therefore, from the point of view of unsaturated soil, the basic properties of unsaturated shaft foundation under cyclic load are studied by using the theory and method of unsaturated soil. It is very necessary to solve the theory of roadbed audit and related engineering technical problems. In view of this, based on the previous work, based on Fredlund's unsaturated soil consolidation theory, the consolidation calculation model of unsaturated soil shaft composite foundation under arbitrary load is established, which is deduced by theory and combined with finite element method. The consolidation problem of unsaturated soil shaft composite foundation under arbitrary load is studied. Firstly, on the basis of Fredlund's consolidation theory equation of unsaturated soil, Darcy's law and Fick's law are combined to establish the differential equation of consolidation of unsaturated soil shaft composite foundation with finite depth under arbitrary load. By means of Laplace transformation, the semi-analytical solutions of the excess pore gas pressure and the excess pore water pressure in the transformation domain are obtained. The variation law of excess pore gas pressure and excess pore water pressure of unsaturated soil under various cyclic loads is analyzed by using a self-compiled program. Secondly, on the basis of previous research, the calculation model is modified and perfected, and the finite element method is used to study the excess pore gas pressure of unsaturated soil shaft composite foundation with finite depth considering smear effect under arbitrary load. The changes of excess pore water pressure and soil settlement were analyzed and studied. Finally, the calculation model is further improved, and finite element method is used to analyze the excess pore gas pressure of unsaturated soil shaft composite foundation with finite depth considering horizontal and vertical two-direction seepage under arbitrary load. The variation law of excess pore water pressure and average consolidation degree of soil is given, and the approximate range of H k wz/kwr relation of soil mass can be neglected in soil consolidation calculation by this soil model. In this paper, based on the objective status quo that the existing consolidation theory of unsaturated soil is updated and demanded by the engineering construction with high speed, the consolidation and settlement law of the unsaturated soil shaft composite foundation under arbitrary load is studied in this paper. The variation law of excess pore gas pressure and excess pore water pressure under various loads in various soil models are given, and the similarities and differences between them are analyzed and compared, which is of great significance for the improvement and development of the consolidation theory of unsaturated soil.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU470

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