盐渍化软土地区砾石桩处理技术及复合地基性状研究

发布时间：2019-03-17 21:46

【摘要】：盐渍土在我国西北地区分布较广，对高速公路工程建设产生很多危害，而随着西部大开发持续推进，高速公路和高速铁路大规模建设，这对盐渍化软土地基处理技术提出了更高的要求。砾石桩是一种重要的盐渍化软土地基加固方法，具有效果良好、施工简便和造价经济等优点，，但目前对于盐渍化软土地区砾石桩复合地基的研究仍处于“应用领先于理论”的阶段，因此本文通过三维拉格朗日有限差分法、室内外试验和理论分析相结合的方法，深入研究了路堤下砾石桩复合地基的工作性状（附加应力场特性和变形规律），并通过具体工程实例进行了验证。本文主要研究成果简述如下：（1）说明砾石桩处理盐渍化软土地基的施工机械和施工技术，分析了盐渍土工程性质研究现状，综述了路堤荷载下桩体复合地基附加应力特性和变形场规律的研究现状，并指出其中存在的问题。（2）通过三维拉格朗日有限差分法模拟研究了路堤荷载下砾石桩复合地基附加应力场特性。明确了桩身应力、桩侧摩阻力沿深度变化规律；相比于均质地基，砾石桩复合地基在桩顶和桩端附近附加应力梯度较大；在路堤下桩体承担了更多的荷载，减少了桩间土附加应力，从而有效控制了沉降；并基于路堤下充分发挥桩体作用的思路，提出褥垫层的厚度和模量。（3）通过三维拉格朗日有限差分法研究了路堤荷载下砾石桩复合地基沉降规律和侧向变形规律。路堤荷载下桩土存在相对位移，桩顶沉降和桩间土沉降随着填土高度的增加均逐渐增大，填土结束后的桩顶沉降和桩间土沉降随固结时间仍逐渐增大直至趋于稳定；侧向位移沿深度呈弓形分布，最大侧向位移发生在软土层内。（4）依托具体工程实例对砾石桩加固盐渍化软弱土地基的效果进行了分析，并通过室内外试验对路堤下砾石桩复合地基工作性状进行了进一步分析，结果表明现场试验与采用FLAC3D计算的结果基本一致，验证了本研究数值模拟计算的正确性和可靠性，较为全面的揭示了盐渍化软土地区砾石桩复合地基的工作性状。
[Abstract]:Saline soil is widely distributed in the northwest of China, causing a lot of harm to highway engineering construction. However, with the continuous development of the western region, the large-scale construction of expressway and high-speed railway has been carried out on a large scale. This puts forward higher requirements for the treatment technology of salinized soft soil foundation. Gravel pile is an important reinforcement method of salinized soft soil foundation, which has the advantages of good effect, simple construction and economical cost. However, the research on gravel pile composite foundation in salinized soft soil area is still in the stage of "applying ahead of theory", so this paper combines the method of three-dimensional Lagrangian finite difference method, indoor and outdoor test and theoretical analysis, In this paper, the working behavior of gravel pile composite foundation under embankment (additional stress field and deformation law) is deeply studied and verified by a concrete engineering example. The main research results of this paper are summarized as follows: (1) the construction machinery and construction technology of gravel pile for treating salinized soft soil foundation are explained, and the research status of the engineering properties of saline soil is analyzed. This paper summarizes the research status of additional stress characteristics and deformation field law of pile composite foundation under embankment load, and points out the existing problems. (2) the additional stress field characteristics of gravel pile composite foundation under embankment load are studied by means of three-dimensional Lagrangian finite difference method. Compared with homogeneous foundation, the additional stress gradient of gravel pile composite foundation near pile top and pile tip is larger than that of homogeneous foundation. The pile under the embankment bears more loads, reduces the additional stress of soil between the piles, thus effectively controls the settlement, and puts forward the thickness and modulus of the cushion based on the idea of giving full play to the role of the pile under the embankment. (3) the law of settlement and lateral deformation of gravel pile composite foundation under embankment load is studied by means of three-dimensional Lagrangian finite difference method. Pile-soil displacement exists under embankment load. Pile top settlement and inter-pile soil settlement gradually increase with the increase of filling height. The pile top settlement and inter-pile soil settlement after filling are still increasing with consolidation time and then tend to be stable. The lateral displacement is arcuate along the depth, and the maximum lateral displacement occurs in the soft soil layer. (4) based on concrete engineering examples, the effect of gravel pile strengthening salinized soft soil foundation is analyzed, and the working behavior of gravel pile composite foundation under embankment is further analyzed through indoor and outdoor tests. The results show that the results of field tests are basically consistent with those calculated by FLAC3D, which verifies the correctness and reliability of the numerical simulation in this study, and reveals the working behavior of gravel pile composite foundation in salinized soft soil area in an all-round way.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

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