基坑降水引起的地表沉降及围护结构位移分析研究

发布时间：2019-01-10 12:41

【摘要】：在地下水位较高的地区进行深基坑施工时,必须在开挖之前进行降水,控制地下水位便于施工并保证基坑的稳定性。降低地下水位从而减少基坑内外水头差是比较常用、有效且经济的措施,但其也会对周围环境造成不良影响,如引起地表不均匀沉降、围护结构变形等。本论文结合某基坑开挖降水实例,分析渗流对基坑外地表沉降及围护结构影响。首先简要介绍了目前基坑工程的发展现状,指出基坑降水存在的问题、常用降水方法及适用范围。通过Midas Gts软件进行有限元模拟,使建立的模型正确反映基坑开挖降水过程。随着基坑开挖深度的增加,支护结构变形逐渐增大,并且最大变形位置发生在开挖面附近；基坑的沉降变形随着开挖深度增加而增大,最大沉降位置发生在16m位置(即一倍开挖深度)：在此基础上,研究考虑渗流与不考虑渗流状态下对基坑开挖的影响。其次对不同开挖阶段下的孔隙水压力、流速等值线进行了研究。离地下连续墙近的孔隙水压值变化最大,离地下连续墙越远,降水开挖对孔隙水压变化影响越小；开挖面墙体附近的流速等值线分布较密,墙体下端地下水在此处有较高的流速；而离墙体越远的地方,流速等值线分布越来越稀疏。最后研究基坑开挖不同影响因素,分别从土体的渗透系数和基坑内的水位变化情况进行分析。得出同时改变x、y、z方向渗透系数,对围护结构、坑外地表沉降及基坑隆起z方向影响远大于xy平面方向的影响：随着基坑内部水位增加,基坑外地表沉降逐渐减少同时,支护结构水平位移随之减少,并随着水位增加发生最大水平位移位置逐渐向上移动趋势,同时抑制基坑底部隆起。
[Abstract]:In the construction of deep foundation pit in areas with high groundwater level, dewatering must be carried out before excavation, and the control of groundwater level is convenient for construction and the stability of foundation pit must be guaranteed. It is common, effective and economical to reduce the water head difference between inside and outside of the foundation pit by lowering the groundwater level, but it will also cause adverse effects on the surrounding environment, such as uneven settlement of the ground surface, deformation of the enclosure structure, and so on. In this paper, the influence of seepage flow on the surface settlement and enclosure structure of foundation pit is analyzed with an example of foundation pit excavation dewatering. Firstly, this paper briefly introduces the development of foundation pit engineering, points out the existing problems of foundation pit dewatering, commonly used dewatering methods and its applicable scope. The finite element simulation is carried out by Midas Gts software to make the model accurately reflect the dewatering process of foundation pit excavation. With the increase of excavation depth, the deformation of supporting structure increases gradually, and the maximum deformation occurs near the excavation surface. The settlement deformation of foundation pit increases with the increase of excavation depth, and the maximum settlement occurs in 16m position (that is, double excavation depth). On this basis, the influence of seepage and non-seepage on excavation of foundation pit is studied. Secondly, the pore water pressure and velocity contour at different excavation stages are studied. The variation of pore water pressure near underground continuous wall is the biggest, and the farther away from underground continuous wall, the less influence of precipitation excavation on pore water pressure change. The distribution of velocity isoline near the wall of excavated surface is relatively dense, and the groundwater at the lower end of the wall has a higher velocity here, and the farther away from the wall, the distribution of velocity isoline becomes more and more sparse. Finally, the factors influencing the excavation of foundation pit are studied, and the seepage coefficient of soil and the variation of water level in the foundation pit are analyzed respectively. It is concluded that the influence of changing the permeability coefficient of xyyangz direction at the same time on the enclosure structure, pit surface settlement and pit uplift z direction is much greater than that of xy plane direction: with the increase of the water level inside the foundation pit, the external surface settlement of the foundation pit decreases gradually, at the same time, The horizontal displacement of the supporting structure decreases and the maximum horizontal displacement position moves upward with the increase of the water level and the uplift at the bottom of the foundation pit is restrained at the same time.
【学位授予单位】：海南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU46

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