荷载作用下软粘土地基土性指标变化规律及承载力研究

发布时间：2018-05-10 06:18

本文选题：软粘土地基 + 不等向固结　；参考：《天津大学》2014年硕士论文

【摘要】：随着我国水运交通行业的迅猛发展,越来越多的港口与海岸工程建设在自然条件较差的深厚软粘土地基上,地基承载力分析的准确性显得尤为重要,会直接影响到工程的安全性与经济性。而目前在使用排水固结法进行软基加固处理时,土体抗剪强度的增长和土性指标的变化趋势尚不明确;另一方面,随着抛石基床、沉箱、填料、胸墙等上部结构物的逐步施工,竖向荷载对地基土体土性指标和地基承载力产生的影响也不容忽视,这些都是实际工程设计中较为关心又亟待解决的问题。本文针对这些问题,结合交通运输部建设科技项目,依托烟台港西港区防波堤二期实际工程,通过进行常规物理性质试验、三轴固结不排水剪切试验以及有限元软件数值模拟,对不同固结压力、不同固结度下软粘土地基的抗剪强度和土性指标变化规律以及地基承载力情况开展了一系列研究工作,主要工作内容如下:(1)通过总结国内外涉及固结度影响的各种试验研究,将固结度的控制方法划分为围压比值法、加载时间法、孔隙水压力法和排水量法四种,并在排水量法的基础上加以改进,开展同时考虑不等向固结压力和固结度两种因素的三轴试验研究。(2)利用ABAQUS软件建立直立式防波堤结构的二维弹塑性有限元数值模型,分析各种工况设计荷载作用下地基土体的竖向位移和上部结构物所产生的附加应力。(3)利用SLB-1型三轴剪切试验仪,对淤泥质粉质粘土原状土样进行室内三轴固结不排水剪切试验,得到荷载作用下土体抗剪强度和土性指标随固结度和轴向偏应力的变化规律,并根据试验数据提出工程设计中考虑荷载作用的土性指标计算公式。(4)对粉质粘土原状土样开展验证三轴试验,证明了所得土性指标变化规律对于软粘土的普遍适用性,给出计算公式的推荐用法。(5)利用有限元数值模型,分别计算采用原始土性指标和考虑荷载作用下土性指标变化的软粘土地基承载力情况,通过对比分析得出采用分级施工方法时软粘土地基承载力会提高约11%的结论。
[Abstract]:With the rapid development of water transportation industry in China, more and more port and coastal projects are built on the soft clay foundation with poor natural conditions. The accuracy of foundation bearing capacity analysis is particularly important. It will directly affect the safety and economy of the project. At present, the increase of soil shear strength and the change trend of soil property index are not clear when using drainage consolidation method to reinforce soft foundation. On the other hand, with the gradual construction of the upper structure, such as rubble bed, caisson, packing, chest wall, etc. The influence of vertical load on soil property index and bearing capacity of foundation soil can not be ignored. These problems are concerned and solved in practical engineering design. In view of these problems, combined with the construction science and technology project of Ministry of Communications and Transport, relying on the actual project of the second phase of breakwater in Xigang District of Yantai Port, through the conventional physical property test, triaxial consolidation undrained shear test and finite element software numerical simulation, A series of research work has been carried out on the variation law of shear strength and soil property index and bearing capacity of soft clay foundation under different consolidation pressure and different consolidation degree. The main work is as follows: (1) by summing up all kinds of experimental studies on the influence of consolidation degree at home and abroad, the control methods of consolidation degree are divided into four kinds: confining pressure ratio method, loading time method, pore water pressure method and displacement method. On the basis of the displacement method, a triaxial experimental study, which takes into account two factors of unequal consolidation pressure and consolidation degree, is carried out. The two-dimensional elastic-plastic finite element numerical model of vertical breakwater structure is established by using ABAQUS software. The vertical displacement of foundation soil and the additional stress produced by superstructure under various design loads are analyzed. The laboratory triaxial consolidation undrained shear test of silty clay samples is carried out by using SLB-1 triaxial shear tester. The variation of shear strength and soil property index with consolidation degree and axial deflection stress under load is obtained. According to the test data, the formula of calculating soil property index considering load in engineering design is put forward. The triaxial test is carried out on silty clay undisturbed soil samples, which proves the general applicability of the change law of soil property index to soft clay. The recommended method of calculation is given. (5) by using finite element numerical model, the bearing capacity of soft clay foundation is calculated by using the original soil property index and considering the change of soil property index under load, respectively. By comparison and analysis, it is concluded that the bearing capacity of soft clay foundation will be increased by about 11% when the method of graded construction is adopted.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U652.2;TU442

【参考文献】