【作者】 胡勇刚；

【导师】 罗强；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2009， 硕士

【摘要】 水泥土搅拌法在20世纪50年代初美国首先研制而成,经过几十年的研究和发展,现在已广泛应用于各国的港湾建设等土木工程建设之中。目前对水泥土搅拌桩的各项力学特性及影响因素已有较深入的研究,但对水泥土搅拌桩复合地基的作用机理理论尚不成熟,还需要进一步研究。国内外对斜坡软弱土地基的研究还在起步阶段,对斜坡软弱土地基的破坏机理认识还不足。为充分掌握斜坡软弱土地基在路堤荷载作用下的变形特性,寻求合理的地基加固措施,在新建达成铁路扩能改建工程某工点进行现场测试研究,并以此为原型,设计了6组基于水泥土搅拌法地基处理方案的室内土工离心模型试验。通过对实验数据的整理分析,有以下主要结论:1)针对斜坡软弱土地基的上、下坡侧分别采取不同的桩间距布设,可减小斜坡软弱土地基沿横向的差异沉降变形,提高地基加固的均匀性;2)在斜坡软弱土地基的下坡一侧布设斜桩,具有较好的水平变形约束效果,但在竖向沉降控制方面表现略差;3)斜坡软弱土地基下坡一侧产生的变形将引起上坡一侧产生相同方向的变形,并以水平变形的表现较明显,地基加固应以控制下坡一侧的变形为重点:4)地基水平变形沿深度的变化规律因地基布桩疏密的不同而表现出先增后减的单峰型曲线和单调衰减的双曲线型两种形态。为充分掌握斜坡软弱土地基在路堤荷载作用下的承载特性,给斜坡软弱土地基的设计提供合理的设计参数。5)斜坡软弱土地基在构造上存在的不均匀性对路堤基底压力分布和桩土荷载分担等力学响应有明显影响,并随软弱土层厚度的增加产生一定的卸载效应和加剧桩土压力的调整;6)采用“上疏下密”不等间距的布桩模式,能调整桩土压力的分布,更好地适应地基软弱土层厚度的变化,提高地基加固的均匀性;7)加筋垫层筋带拉力受路堤荷载、软弱土层厚度和桩体布置间距等因素的共同影响,分布形态表现出显著的不对称性特点,最大值出现部位与斜坡软弱土地基可能产生的变形破坏位置有良好的一致性。更多还原

【Abstract】 Mixed-in-Place pile was first developed successfully in the United States at the beginning of 1940s, after decades of research and development, which has been widely used in Civil engineering, such as the Harbor construction, in many countries. At present, it has been intensively studied about the mechanical properties and influencing factors of the cement -soil mixing pile, but the theory of the mechanism on composite foundation of the cement -soil mixing pile has not mature, which needs to further study. The research on slope soft-soil foundation is in initial stage, and the understanding on the failure mechanism of slope soft-soil foundation is inadequate.In order to fully master the deformation characteristics of slope soft-soil foundation under loads of embankment and find to reasonable strengthening measures of the foundation, there’s a field test at a research site in new-building capacity expansion and conversion project between DAZHOU and CHENGDU. This essay uses the above project as a prototype, and designs 6 groups indoor geotechnical centrifuge model tests based on the foundation processing program of the Mixed-in-Place pile. Through the collation and analysis of the experimental data, the main conclusions are as follows:1)By adopting different pile spacing layout style at the upside and downside direction of the slope, it can reduce the differ deformation of the slope soft-soil foundation along the lateral side and improve the uniformity of the foundation treatment;2) It has better deformation binding effect by setting up the tilted pile in the downhill side of the slope soft-soil foundation, but it has less effective performance in controlling the vertical subsidence;3) The slope soft-soil foundation deformation that appeared at the downhill side will give rise to the same direction deformation at the uphill side, and the horizontal deformation is more obvious. The foundation treatment should put emphasis on the deformation controlling of downhill side;4)The varying law about horizontal deformation along the depth direction shows para-curve style which is first adding then reducing and hyperbola style that is humdrum reducing, attribute to the density of the pile layout.5) The non-uniformity of the slope soft-soil foundation in the structure has significantly effects on the mechanical response of the foundation, such as the pressure distribution and load-sharing;6) The use of the varying pile spacing mode can adjust the distribution of pile-soil pressure, and better adapt to the change of the thickness of the soft-soil foundation and improve the uniformity of foundation strengthening;7)The pulling force of the reinforced cushion geobelt is combined effected by many factors, such as the embankment loading, the thickness of soft-soil foundation and pile spacing arrangement. The distribution patterns has significant feature of the asymmetry. There is good consistency between the appearing position of the maximum value and the possible deformation location of the slope soft-soil foundation.更多还原