富森大厦基坑变形监测及变形机理研究

发布时间：2018-06-30 19:41

本文选题：基坑支护 + 基坑监测　；参考：《湖南科技大学》2017年硕士论文

【摘要】：基坑工程是集岩土工程和结构工程等多学科于一体的系统工程,综合性强,影响因素多。在基坑开挖过程中,原有土体稳定状态将被打破,出现侧面临空的状态,发生应力重分布,导致土体出现不稳定的现象,引发工程安全性问题。为保证施工安全,就需要进行支护工程,因此对于基坑开挖后土体与支护结构之间的相互作用成了设计过程中人们最关心的问题。深圳富森基坑工程位于光明新区龙大高速东侧,华夏二路南侧。场地内自上而下地层大体可分为五大层,即人工填土层(Q4ml)、湖积层(Q4l)、冲洪积层(Q3al+pl)和残积层(Qel),下伏基岩为震旦系混合岩(Z)。基坑支护采用复合土钉墙设计,分别采用放坡加土钉加微型桩加锚索,土钉锚索加微型桩,以及桩锚支护的支护形式。现场监测工作中共设置14个水平、垂直位移观测点,监测施工过程中基坑壁上产生的水平、垂直位移。并设置了4个水位观测点,观测基坑止水帷幕渗漏问题。最终得到的监测结果可以发现最大位移在基坑壁中部,水平位移最大达到25mm,垂直位移最大达到21mm,证明了该基坑施工过程的安全性。本文通过FLAC3D软件的数值模拟,建立了富森基坑三维模型,分析基坑开挖支护前后应力应变情况。支护前后对比发现,最大、最小主应力较大程度的减小,在进行支护后,最大、最小主应力最大值区域整体范围向着支护桩体靠近。在基坑底靠近坡脚的位置,最大、最小主应力值相对偏大,存在应力集中现象,从而引起在基坑底部土体水平位移值偏大,说明这个部位受力状况比较复杂,导致基坑底部支护桩位置有较大的剪应变产生;并可以发现基坑尺寸对最大主应力分布有一定的影响。基坑水平位移最大值集中在中上部,并且方向向着基坑内部。进行支护后由于支护结构的支撑使得沉降最大位置不在基坑坡顶开挖边线处,其墙后沉降整体分布形式类似勺状,基坑沉降最大值发生在基坑坡顶距离开挖边线5.0~8.0m的位置。放坡支护在开挖到一定深度之前对应力有缓解作用;在基坑坡脚存在着应力集中现象,使得基坑坡脚位置水平位移相对较大;在基坑开挖到一定程度后,基坑开挖尺寸开始对基坑应力应变起重要作用。本文通过FLAC3D软件的有限差分法得到的相关结论可以为类似工程设计施工提供一定的借鉴。
[Abstract]:Foundation pit engineering is a systematic engineering with many disciplines such as geotechnical engineering and structural engineering. During the excavation of foundation pit, the stable state of the original soil will be broken, and the condition of side face will appear, and the stress redistribution will occur, which will lead to the unstable phenomenon of soil mass and cause the engineering safety problem. In order to ensure the safety of construction, it is necessary to carry out support engineering, so the interaction between soil and supporting structure after excavation has become the most concerned problem in the design process. Shenzhen Fusen Foundation Pit Project is located in the east of Longda Expressway, Guangming New area, and south of Huaxia Road 2. The upper and lower strata in the site can be divided into five layers, I. E. artificial filling soil layer (Q4ml), lacustrine layer (Q4l), alluvial layer (Q3alpl) and residual layer (Qel), and the lower voluminous rock is Sinian migmatite (Z). The composite soil nailing wall is used to support the foundation pit, and the supporting forms of the pile and anchor support are adopted, respectively, such as slope placement plus soil nailing plus micro pile plus anchor cable, soil nail anchor cable plus micro pile, as well as the support form of pile anchor support. A total of 14 horizontal and vertical displacement observation points were set up in the field monitoring work to monitor the horizontal and vertical displacement in the foundation pit wall during the construction process. At the same time, four water level observation points were set up to observe the leakage of water stop curtain in foundation pit. The monitoring results show that the maximum displacement is 25 mm for horizontal displacement and 21 mm for vertical displacement in the middle of the foundation pit wall, which proves the safety of the foundation pit construction process. In this paper, through numerical simulation of FLAC3D software, a three-dimensional model of Fucson foundation pit is established, and the stress-strain situation before and after excavation is analyzed. Before and after supporting, it is found that the maximum and minimum principal stresses decrease to a large extent, and after supporting, the maximum and minimum principal stresses of the whole region are close to the supporting pile body. At the bottom of the foundation pit near the foot of the slope, the maximum and minimum principal stress values are relatively large, and there exists the phenomenon of stress concentration, which causes the horizontal displacement of the soil at the bottom of the foundation pit to be larger, which indicates that the stress condition of this part is relatively complex. It can be found that the size of foundation pit has a certain influence on the distribution of maximum principal stress. The maximum horizontal displacement of foundation pit is concentrated in the middle and upper part, and the direction is toward the inside of foundation pit. After supporting, the maximum position of settlement is not located at the edge line of the slope top of foundation pit, and the overall distribution of settlement behind the wall is similar to that of ladle. The maximum settlement of foundation pit occurs at the position of 5.0 ~ 8.0 m from the slope top of foundation pit to the edge line of excavation. Slope support can alleviate stress before excavation to a certain depth; stress concentration phenomenon exists at the foot of foundation pit, which makes the horizontal displacement of foundation pit slope foot relatively large; after excavation to a certain extent, The excavation size of foundation pit plays an important role in the stress and strain of foundation pit. The conclusions obtained by finite difference method of FLAC3D software can be used for reference in the design and construction of similar projects.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU433

【参考文献】