考虑流固耦合作用的深基坑降水工程环境影响研究

发布时间：2018-03-20 14:14

本文选题：基坑工程　切入点：降水开挖　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前,城市建设日益加快,基坑施工问题日益突出,为了有效把握施工进度、改善降水开挖对基坑施工影响、缓解基坑降水对周边环境影响,因此选取建设环境相对典型的城中村改造项目某回迁楼基坑作为分析对象,按照施工要求,对太原市的某基坑工程降水开挖过程做了数值模拟,详细分析了降水开挖对基坑周边环境产生的影响,为本基坑工程的顺利施工提出参考依据,也为下一步的基坑降水工程积累了经验。为了研究降水开挖中各个参数对周边环境的影响,本文详细介绍了地下水渗流基本理论和基坑降水理论。采用FLAC3D建立模型,采用流固耦合的方式进行计算,得出了相关参数的影响作用的大小。⑴以太原市的某基坑工程作为研究对象,根据岩土勘察结果和试验报告,然后利用FLAC3D有限差分软件,对比了未开挖前降水情况下与开挖降水过程后基坑中孔隙水压力、基坑水平位移和竖向变形的变化情况。并把数值模拟所得结果与实际监测进行了对比。⑵对太原某基坑工程进行考虑流固耦合情况下的数值模拟分析,应用FLAC3D程序分析了工程降水引起基坑周边地面变形的规律,包括止水帷幕深度、抽水井深度、抽水井井距、回灌井数量等因素对基坑周边地面变形产生的影响。根据上述的分析得出结论:⑴基坑降水使土体孔隙水压力逐渐下降,形成“降水漏斗”。受止水帷幕作用,基坑外部孔隙水压力降幅较小,基坑开挖工序对基坑外部土体孔隙水压力的变化没有影响。⑵模拟所得基坑内外地面沉降、基坑水平变形分布规律与实测值基本吻合,误差在允许范围之内。⑶止水帷幕深度变化时,开挖前降水过程中,帷幕深度对基坑内部孔隙水压力分布、基坑内部竖向位移的影响可以忽略不计,在基坑外部,帷幕深度越大,其止水效果越好,受地面最大沉降量和沉降范围越小。⑷当抽水井深度超过18m后,基坑内部的孔隙水压力降幅增加量有限,当抽水井深度超过帷幕深度时,基坑外部部分地下水直接平行进入抽水井,使得基坑外部土体发生较大沉降,仅提高降水井深度来增强基坑降水效果,一定范围内是不合理的。⑸抽水井井距为10m和12m时,抽水完成后,基坑内部孔隙水压力分布基本相同,随着井距的继续增加,其抽水能力将无法满足基坑开挖的需要,因此,实际工程中应该合理的选择井距。⑹对于设置回灌井,在止水帷幕下端,回灌井数量越多,该处孔隙水压力的变化越小,地面沉降大幅度的降低,此外,回灌井的布设还缩小沉降的影响范围。
[Abstract]:At present, urban construction is speeding up day by day, and the problem of foundation pit construction is becoming increasingly prominent. In order to effectively grasp the construction progress, improve the influence of dewatering excavation on foundation pit construction and alleviate the impact of foundation pit dewatering on the surrounding environment, Therefore, the foundation pit of a return building which is a typical urban village reconstruction project is selected as the analysis object. According to the construction requirements, the process of dewatering excavation of a foundation pit in Taiyuan city is numerically simulated. The influence of dewatering excavation on the surrounding environment of foundation pit is analyzed in detail, which provides a reference basis for the smooth construction of this foundation pit project. In order to study the influence of various parameters on the surrounding environment, the basic theory of groundwater seepage and the theory of foundation pit dewatering are introduced in detail in this paper. FLAC3D is used to establish the model. The fluid-solid coupling method is used to calculate, and the magnitude of the influence of relevant parameters is obtained. 1. Taking a foundation pit project in Taiyuan as the research object, according to the results of geotechnical investigation and test report, and then using FLAC3D finite difference software, The pore water pressure in foundation pit before excavation and after excavation is compared. The variation of horizontal displacement and vertical deformation of foundation pit is analyzed. 2. The numerical simulation results are compared with the actual monitoring results. 2. The numerical simulation analysis of a foundation pit project in Taiyuan considering fluid-solid coupling is carried out. The rules of ground deformation around foundation pit caused by engineering dewatering are analyzed by using FLAC3D program, including the depth of sealing curtain, the depth of pumping well, the distance of pumping well. Based on the above analysis, it is concluded that the dewatering of foundation pit at 1 / 1 makes the pore water pressure of soil gradually decrease and form a "dewatering funnel". The decrease of pore water pressure outside the foundation pit is relatively small, and the variation of pore water pressure of soil outside the foundation pit is not affected by the excavation procedure. 2. The ground subsidence inside and outside the foundation pit is simulated, and the horizontal deformation distribution law of the foundation pit is basically consistent with the measured value. In the process of dewatering before excavation, the influence of curtain depth on pore water pressure distribution and vertical displacement of pit can be ignored when the error is within the allowable range of .3 depth of waterproof curtain. The greater the depth of curtain is outside the foundation pit, the greater the depth of curtain is. The better the sealing effect is, the smaller the maximum subsidence and settlement range are. 4. When the depth of pumping well exceeds 18 m, the increase of pore water pressure in foundation pit is limited, and when the depth of pumping well exceeds the depth of curtain, the increase of pore water pressure is limited. The underground water from the outside of the foundation pit enters the pumping well in parallel directly, which makes the soil in the outside of the foundation pit settlement larger, and only increases the depth of the dewatering well to enhance the dewatering effect of the foundation pit. In a certain range, it is unreasonable that the interval between the pumping wells and the pumping wells is 10m and 12m. After pumping, the distribution of pore water pressure in foundation pit is basically the same. With the increase of well spacing, its pumping capacity will not be able to meet the needs of foundation pit excavation. At the lower end of the curtain, the more the number of recharge wells, the smaller the change of pore water pressure and the decrease of ground subsidence. In addition, the layout of recharge wells also reduces the influence range of settlement.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753.66

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