【作者】 王超；

【导师】 朱杰；

【作者基本信息】 安徽理工大学 ， 建筑与土木工程， 2019， 硕士

【摘要】 随着社会经济的不断发展,城市用地日趋严重,兴建了大量城市地下工程,使得基坑工程不断向着更大更深的方向发展。支护结构在施工过程中的变形量与深基坑的工程质量有着密切的联系,选用支护方式从安全、可靠、经济适用这几个方面考虑是十分必要的。桩锚支护与其他支护方式相比适应性更强,能够有效约束土体的滑动破坏,限制基坑土体的位移,节省工程造价,是深基坑一种非常常用的支护方式。影响桩锚支护结构变形的因素有许多,但目前对桩锚支护结构变形影响因素的研究还存在一些差距。本文以蒙自锦隆财富深基坑工程为背景,使用有限元软件MIDAS/GTS建立三维模型,对动态施工过程进行模拟。主要内容如下:(1)通过查阅相关文献和资料,概述基坑支护方式的特点、使用范围和桩锚相互作用机理,总结支护桩和锚索的设计方法,为后续研究提供理论基础。(2)介绍现场地质及周边环境条件,对支护方案进行简介,采用MIDAS/GTS建立三维有限元模型。(3)依据工程设计建立有限元模型,根据具体施工工序建立分布工况,分析支护体系在动态施工过程中的内力、位移变化规律。模拟结果显示支护桩最大水平位移出现在桩顶位置,为26.14mm,支护桩的最大负剪切力发生在桩身中部,最大正剪切力发生在桩身中下部,支护桩的最大负弯矩发生在桩身中上部,最大正弯矩发生在桩身中下部,基坑周边土体沉降在距基坑边7m处达到最大沉降量8.72mm。将模拟值与监测值进行分析对比,模拟值和监测值相差不大,验证了有限元方法的可行性和有效性,为后续研究提供有效的数值模型。(4)分析桩径、桩间距、桩长、锚索竖向间距和水平间距对支护桩水平位移、弯矩和地表沉降的影响,当桩径或桩长增加,或者减小桩距时,能有效抑制支护桩的水平位移,但桩径和桩间距存在一有效值,当超过这个有效值时,对支护桩变形的影响不明显,桩径和桩间距的变化会改变支护桩的弯矩大小,但是不会改变反弯点的位置,通过在造价方面的对比,发现减小桩径的方法在保证基坑稳定和减小造价这两个方面都能兼顾,锚索竖向间距宜在2～2.5m之间。图:39表:12参:73更多还原

【Abstract】 With the continuous development of social economy,urban land use is becoming more and more serious,and a large number of urban underground projects have been built,which makes the foundation pit project continue to develop in a larger and deeper direction.The deformation of supporting structure in the construction process is closely related to the engineering quality of deep foundation pit.It is necessary to select the supporting method from the aspects of safety,reliability and economic applicability.Pile-anchor support is more adaptable than other supporting methods,which can effectively restrain the sliding failure of soil,limit the displacement of foundation pit soil,and save engineering cost.It is a very common supporting method for deep foundation pit.There are many factors affecting the deformation of pile-anchor retaining structure,but there are still some gaps in the study of the factors affecting the deformation of pile-anchor retaining structure.Based on the background of Jinlong Fortune Deep Foundation Pit Project in Mengzi,this paper uses finite element software MIDAS/GTS to build a three-dimensional model to simulate the dynamic construction process.The main contents are as follows:(1)Through consulting relevant literature and information,the characteristics and application scope of foundation pit support mode,interaction mechanism and destructive characteristics of Pile-anchor support are summarized,and the analysis theory of support structure is summarized,which provides theoretical basis for subsequent research.(2)This paper introduces the site geology and surrounding environmental conditions,briefly introduces the support scheme,and establishes a three-dimensional finite element model using MIDAS/GTS.(3)Based on the engineering design,the finite element model is established,and the distribution condition is established according to the specific construction procedure.The variation law of internal force and displacement of the support system in the dynamic construction process is analyzed.The simulation results show that the maximum horizontal displacement of supporting piles occurs at the top of piles,which is 33.01mm.The maximum negative shear force of supporting piles occurs in the middle and lower parts of piles.The maximum negative bending moment of supporting piles occurs in the middle and upper parts of piles.The maximum positive bending moment occurs in the middle and lower parts of piles.The settlement of soil around the foundation pit reaches the maximum settlement of 8.72mm 7 m away from the edge of the foundation pit.By comparing the simulated value with the monitored value,it is found that there is little difference between the simulated value and the monitored value,which verifies the feasibility and validity of the finite element method and provides an effective numerical model for the follow-up study.(4)The influence of pile diameter,pile spacing and pile length on the horizontal displacement and bending moment of supporting pile is analyzed.When pile diameter or pile length increases or decreases,the horizontal displacement of supporting pile can be effectively restrained,but there is an effective value of pile diameter and pile spacing.When the effective value is exceeded,the influence on the deformation of supporting pile is not obvious.The change of pile diameter and pile spacing will change the bending moment of supporting pile,but the effect is not obvious.By comparing the construction cost,it is found that the method of reducing pile diameter can take into account both the stability of foundation pit and the reduction of construction cost.The vertical distance between anchor cables should be between 2 and 2.5 m.Figure[39]table[12]reference[73]更多还原