复合土钉墙支护结构在深基坑工程中的应用研究

发布时间：2018-02-04 03:24

本文关键词： 复合土钉墙支护微型桩变形影响因素　出处：《西安建筑科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：复合土钉墙支护技术具有施工简便、造价低廉和支护效果良好等显著优点而在深基坑工程中得到广泛应用。目前对该支护形式的作用机理研究较少,相应理论也不够完善,设计偏于保守,造成了巨大的资源浪费。为了使复合土钉墙支护技术更好的应用于工程实践,对其作深入的研究十分必要。本文以西安某深基坑工程为研究背景,对常见的深基坑工程支护方案进行比较分析,采用微型桩+土钉的复合支护结构。基于ABAQUS有限元软件建立三维模型,模拟基坑开挖的全过程,模拟过程中考虑了土钉、微型桩和土体的粘结滑移作用,各构件之间采用节点位移耦合的方法。通过与现场实测数据对比分析,验证了ABAQUS模拟支护结构的受力变化和基坑变形的合理性。通过合理的模型,分析归纳出土钉、微型桩和面层的参数对基坑变形的影响规律,找出最优设计值并优化原方案,为同类工程的设计和施工提供参考。本文的主要研究成果如下:(1)微型桩+土钉复合支护结构在控制边坡位移方面有显著的效果。边坡水平位移表现出顶部小,中部大的“鼓肚”型分布,并且下部有收敛趋势。地表沉降最大值出现在离开挖面一定位置处,最后趋于稳定;坑底隆起值距离开挖面越远越大,最后趋于稳定。(2)从上至下,前二排土钉轴力呈现两端小,中部较大的“枣核”型分布,从第三排土钉之后,最大轴力逐渐向开挖面移动且距离面层一定距离,其中土钉的最大轴力出现在第三排。第四排和第五排土钉轴力最大值出现在开挖面附近,说明此处坑壁坡脚剪应力集中,容易发生事故。(3)基坑每步开挖支护后,微型桩出现的最大剪力均为负剪力,方向朝基坑的外侧。随着开挖步的进行,对应的最大剪力值也不断增大,到了开挖底面位置,剪力的绝对值最大,在微型桩嵌入到坑底以下一定深度的时候,剪力值又变为0。(4)复合土钉墙支护结构中,土钉的布置方式、长度、直径、水平间距、倾角和微型桩的间距及面层的厚度是基坑变形的主要影响因素;微型桩的直径和入土深度对控制基坑变形的效果不明显。
[Abstract]:Composite soil nailing wall support technology has been widely used in deep foundation pit engineering because of its advantages such as simple construction, low cost and good support effect. The corresponding theory is not perfect, the design is conservative, resulting in a huge waste of resources. In order to make the composite soil nailing wall support technology better applied in engineering practice. It is necessary to make a deep research on it. This paper takes a deep foundation pit project in Xi'an as the research background to compare and analyze the common support schemes of deep foundation pit engineering. Using the composite support structure of micro-pile and soil nailing, a three-dimensional model based on ABAQUS finite element software is established to simulate the whole process of foundation pit excavation, and soil nailing is considered in the simulation process. The bond-slip effect of micro-pile and soil is analyzed by using the method of joint displacement coupling between the components. The results are compared with the field measured data. Through the reasonable model, the influence of soil nailing, micro-pile and surface layer parameters on foundation pit deformation is analyzed and concluded. Find out the optimal design value and optimize the original scheme. To provide reference for the design and construction of similar projects. The main research results of this paper are as follows: 1). The micro-pile soil nailing composite support structure has remarkable effect in controlling the slope displacement. The horizontal displacement of the slope is small at the top. There is a large "bulge" type distribution in the middle part, and the lower part is convergent. The maximum value of surface subsidence appears at a certain position from the excavated surface and tends to be stable at last. From top to bottom, the axial force of the first two rows of soil nailing shows the distribution of "jujube core" type with small ends and large middle part, after the third row of soil nailing. The maximum axial force gradually moves to the excavated surface and is far from the surface layer, in which the maximum axial force of soil nailing appears in the third row. The maximum axial force of 4th row and 5th row of soil nailing appears near the excavated surface. It shows that the shear stress concentration at the foot of the pit slope is easy to happen. 3) after every step of excavation of foundation pit, the maximum shear force of micro pile is negative shear force, which is oriented towards the outside of foundation pit. The corresponding maximum shear value is also increasing. At the bottom of the excavation, the absolute value of the shear force is the largest, when the micro-pile is embedded in a certain depth below the bottom of the pit. In the composite soil nailing wall support structure, the layout, length, diameter, horizontal spacing, inclination angle, spacing of the micro-pile and the thickness of the surface layer are the main influencing factors of foundation pit deformation. The effect of the diameter and depth of the micro pile on controlling the deformation of foundation pit is not obvious.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753

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