摘要
随着我国经济发展和城市建设现代化的不断提高,人们开始越来越多的对高空与地下空间进行规划利用。大型深基坑工程是高层建筑和城市地下工程的重要组成部分。在深基坑工程的施工中,围护结构的稳定性对基坑稳定性有主要影响。本文结合北京地铁奥运支线大屯路公交换乘站基坑工程,在以下几方面进行了较为深入的研究:
分析了深基坑围护形式和计算理论研究现状。对影响深基坑变形主要因素如墙体变形、坑底隆起、周围地表及建筑物的沉降等以及影响深基坑稳定的主要因素如水文地质、基坑规模及土压力值、设计方案及施工方法的合理性等进行了较为系统的分析。
依据大屯路公交换乘站工程概况和设计要求,进行了支护类型选取并进行计算,确定支护方案。利用FDM方法对支护结构模拟,结合大屯站基坑实际工程中拟建立的典型工况,得到主要变量如应力和位移等等的空间变化规律。
对大屯路公交换乘站基坑的施工过程进行了现场监测。提取并整理了锚索内力、围护桩的水平位移及内力和钢支撑的轴力的数据进行分析。得出了在刚支撑作用下,随基坑开挖的围护桩变形曲线、最大水平位移位置和桩顶部分段的倾斜等规律,并研究了钢支撑对支护结构的约束作用和轴力变化。
将监测所得数据与设计方案模拟计算结果进行对比,提取围护桩桩身水平变形数据,现场监测所得的位移趋势与数值计算所得的变形趋势大体上是一致的,为进一步对支护结构的研究提供了较为可靠依据。
结合FLAC 3d对基坑开挖的支护情况进行三维数值模拟,考虑开挖空间效应、层内钢支撑的间距、对撑与角撑的关系及钢支撑的刚度等因素对基坑结构的稳定性的影响规律,并提出了相应的基于变形控制的支护体系优化设计方法。
通过本文的研究,加深了地铁深基坑支护体系的认识,研究结果在深基坑支护结构理论分析、设计优化和计算等方面具有一定的参考价值。
With the implementation of economic development and the growing urbanization in China, people pay more and more attention to the exploitation of the higher space and underground space. Large-scale foundation pit engineering is the important element of the high-rise buildings and urban underground engineering. In the construction process of the deep foundation pit, the stability is one of the problems which pay most close attention. In the issue of the foundation pit stability, the stability of the retaining system is the chief part. Based on this, the author intensifies research on these aspects:
analyzing of the formality of retaining formality and the currently research state of the calculate theory, and integrating them organically, the result indicates that, the deformation of deep excavation consists of pile-wall’s deformation, swelling of pit bottom and the subsidence of the earth and buildings around the excavation. The main factors affecting the stability of deep excavation are hydro-geologic condition, the soil press and the scale of the excavation, the design plan and the construction method. The reasonable support style and scheme and the information construction method should be taken to protect the safety of deep foundation pit and adjacent structure; The retaining scheme and the monitoring plan of the foundation pit of DaTun Road station are given in this paper. After distilling and collation the data of the pile-wall’s deformation, cable stress and the axis force of the steeled support. The result find out the deformation curve and the variation laws of the steeled support axis force, and the result indicates that the x-displacement of the pile-wall could be the important evaluation index which shows the safety state of the retaining construction; Using the FDM software FLAC 3dto simulate the retaining state of the deep excavation to the foundation pit, gave the rule of the influence laws to the stability of the foundation pit. The influence include excavation space effect, interval of each steeled support in one layer, relation between the x-steeled support and oblique steeled support and the stiffness of the steeled support et cetera. Then in corresponding, bring up the measures for retaining system’s optimization design on the basis of deformation control.
Through the research, deepened the understanding to the retaining system in deep foundation pit of the subway station, and the research findings provided some theoretical basis for theoretical analysis, optimization design and calculation of the retaining in deep foundation pit.
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