地连墙基坑开挖中渗流作用对基坑变形的影响

发布时间：2019-03-28 20:38

【摘要】：随着建筑规模越来越大,深基坑工程不断出现,而基坑深度的不断加深使得基坑变形成为基坑支护最重要的安全指标。在基坑的各种支护方案中,地连墙因刚度大、变形小、安全保障性好、兼可与逆作法相结合作为主体结构的结构形式得到广泛的应用,关于地连墙基坑变形的研究也随之增多。但地下水渗流作用作为影响基坑变形的主要因素之一,相关研究却相对匮乏,尤其是将土体孔隙水的渗流单独分离出来进行的研究更为稀少。本文采用有限元模拟方法将基坑的降水过程作为独立分析步进行模拟,通过考察降水分析步前后的基坑变形变化,探究土体孔隙水的渗流作用对基坑变形的影响。主要研究内容如下：(1)介绍有限元模型的参数选用和分析步、接触等具体问题的处理,将整个基坑的开挖过程分为降水和开挖两个分析步来区分两个不同的过程所引起的基坑变形。通过采用所介绍的模拟方法对一个基坑工程实例进行模拟,将模拟结果与实测结果进行对比以验证其适用性。(2)在研究各因素的影响之前,确立一个用作对比标准的基准模型。对该基准模型的有限元模拟结果进行分析,详细叙述了采取该模拟方式时基坑的各项变形大小和特征。将地连墙的侧向变形、基坑外土体沉降和基底隆起作为基坑变形对比项,并分析降水过程所导致的基坑各项变形在总变形中所占的比重。(3)改变地连墙的入土深度,将各种深度地连墙基坑的变形分析结果进行对比,得出地连墙的入土长度对基坑各项变形以及渗流作用大小的影响。改变土体的渗透系数、孔隙比和回弹指数,同样对基坑各项变形和降水过程的变形所占比例进行分析,探究土体参数对基坑变形和渗流作用大小的影响。(4)研究两种减小渗流影响的措施：地连墙嵌入基岩、在基坑外围设置降水井。对两种措施进行有限元模拟,除了措施相关参数在有限元模型中有所区别,其他参数均与对比模型相同,将模拟结果与基准模型的结果进行对比,得出两种措施的作用大小。
[Abstract]:As the scale of the building is becoming larger and larger, the deep foundation pit works continuously, and the depth of the foundation pit is increasing, so that the deformation of the foundation pit becomes the most important safety index of the foundation pit support. In the various supporting schemes of the foundation pit, the ground connection wall is widely used because of the large rigidity, small deformation, good safety and security, and can be combined with the reverse construction as the structure of the main body, and the research on the deformation of the foundation pit of the ground connection wall is also increased. However, the seepage of groundwater is one of the main factors that affect the deformation of the foundation pit, and the related research is relatively scarce, especially the research on the separate separation of the pore water of the soil. In this paper, the precipitation process of the foundation pit is simulated by the finite element simulation method, and the effect of the seepage of the soil pore water on the deformation of the foundation pit is studied through the study of the deformation of the foundation pit before and after the precipitation analysis step. The main contents of the research are as follows: (1) The process of selecting and analyzing the parameters of the finite element model is introduced, and the excavation process of the whole foundation pit is divided into two analysis steps of precipitation and excavation to distinguish the deformation of the foundation pit caused by two different processes. The simulation results are compared with the measured results to verify the applicability of a foundation pit engineering case by using the described simulation method. (2) A baseline model used as a reference standard was established prior to the study of the impact of the factors. The finite element simulation results of the reference model are analyzed, and the deformation and the characteristics of the foundation pit are described in detail. The lateral deformation of the ground connecting wall, the settlement of the soil mass outside the foundation pit and the base uplift are used as the comparison items of the deformation of the foundation pit, and the specific gravity of the deformation of the foundation pit caused by the precipitation process in the total deformation is analyzed. (3) To change the depth of the ground connection of the wall, compare the deformation and analysis results of the foundation pit with various depth, and obtain the effect of the length of the earth-connecting wall on the deformation of the foundation pit and the size of the seepage. The permeability coefficient, the ratio of porosity and the rebound index of the soil body are changed, and the proportion of the deformation of the foundation pit and the deformation of the precipitation process is also analyzed, and the influence of the soil parameters on the deformation and seepage effect of the foundation pit is studied. (4) Two measures to reduce the influence of seepage: the ground connection wall is embedded in the bedrock, and the dewatering well is set on the periphery of the foundation pit. The finite element simulation of the two measures, except that the relevant parameters of the measures differ in the finite element model, the other parameters are the same as the comparison model, and the simulation results are compared with the results of the reference model to obtain the effect of the two measures.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753

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