【作者】 王浩；

【导师】 吴燕开；

【作者基本信息】 山东科技大学 ， 岩土工程， 2020， 硕士

【摘要】 当前,国内地下轨道交通的建设正在如火如荼的进行,随之涌现出了大量深大基坑工程。而基坑周边往往环境复杂、构筑物繁多、管线密集,这就使得基坑施工过程变得极为复杂,在其施工过程中导致的安全事故和引发的环境问题更是层见叠出。可见,基坑工程结构自身的安全至关重要,同时保证其周边环境的安全与稳定也不容忽视。本文以济南市轨道交通1号线的烈士陵园地铁车站深基坑工程为依托,在现场监测的基础上,结合有限元数值模拟,分析研究了深基坑降水开挖过程中引起的基坑变形、周边地表沉降以及对建筑物基础沉降的影响。(1)对深基坑的降水方法和适用条件进行了归纳总结,分析了深基坑降水、开挖引起的土体变形机理以及控制基坑变形的有关措施等,为地铁车站深大基坑降水开挖变形特性的研究提供了基础。(2)依据济南市轨道交通1号线此地铁车站深基坑现场施工过程的监测数据,从中选择具有代表性的监测点进行具体的数据分析,对该基坑周围土体沉降、围护结构变形、临近建筑物基础沉降三个方面进行分析。并对降水开挖引起的变形进行了总结:处在基坑长边地表沉降点的测值较短边地表沉降点的测值要大一些;基坑降水开挖的初期,围护结构的位移仅产生在桩体的顶部,水平位移的极值点会随降水开挖深度的增大而逐渐向桩体的下部移动,其极值点最终出现在距桩体底部三分之一左右的位置;周围建筑物基础沉降的最大点距离基坑边缘最近,而距离基坑较远的建筑物沉降监测点,在基坑开挖不久则出现向上隆起的趋势。(3)基于ABAQUS的流固耦合模块建立了考虑基坑开挖全过程的三维有限元模型,整个模拟过程分为六步降水、六步开挖,每一次水位都降到开挖面以下0.5m的位置,并将数值模拟结果与实测数据和理论计算进行对比验证,对基坑动态降水及开挖导致的主体结构变形特点进行了深入探讨。对于围护结构的变形,第一步降水产生的影响较小,第二步降水产生的影响最为突出,第二步降水后,降水对于围护结构产生的变形影响越来越弱,到第六步降水时,其对围护结构的变形起到了积极的作用,在一定程度上减小了围护结构的变形;关于坑周地表的沉降,降水所引起的地表沉降值均小于开挖所造成的地表沉降值,其中,第五步降水对地表沉降造成的影响最为明显,其对地表造成的沉降影响达到了地表沉降总值的14.2%。(4)通过数值模拟分别分析降水与不降水、不同降水方式、不同降水速度和深度以及建筑物距基坑不同距离的影响因素下,基坑和周边环境变形的基本规律。与隔层降水以及一次性降水方式相比,逐层降水的方式对于基坑自身的稳定性以及周边环境的影响要小;基坑降水的速度和深度存在最优值,当降水速度和深度皆达到最优值时,对控制基坑稳定性有一定的作用;相比降水深度,降水速度对基坑变形影响不大。更多还原

【Abstract】 At present,the construction of domestic underground rail transit is in full swing,and a large number of deep and large foundation pit projects have emerged.The surrounding environment of the foundation pit is often complex,with many structures and dense pipelines,which makes the construction process of the foundation pit extremely complicated,and the safety accidents and environmental problems caused by the construction of the foundation pit are overlapping.It can be seen that the safety of the foundation pit engineering structure itself is very important,while ensuring the safety and stability of its surrounding environment can not be ignored.Based on the background of the deep foundation pit project of the Martyrs Cemetery Metro Station of Jinan Rail Transit Line 1,this paper analyzes the deformation of the foundation pit,the settlement of surrounding surface and the impact of building foundation settlement caused by the precipitation excavation of the deep foundation pit through on-site monitoring combined with finite element numerical simulation.(1)Systematically summarize the method and applicable conditions of deep foundation pit precipitations,and analyze the soil deformation mechanism caused by deep foundation pit precipitation,excavation,and related measures to control the deformation of the foundation pit.The study on the deformation characteristics of pit precipitation excavation provides the basis.The study of excavation deformation characteristics provides the basis.(2)According to the monitoring data of the site construction process of the deep foundation pit of this subway station of Jinan Rail Transit Line 1,the paper selects a representative set of monitoring points for specific data analysis.The three aspects of soil settlement around the foundation pit,deformation of the enclosure structure,and foundation settlement of the adjacent building were analyzed.The deformation law caused by precipitation excavation is summarized:the measured value of the surface settlement point on the long side of the foundation pit is larger than the measured value on the shorter side of the foundation pit;In the early stage of precipitation excavation of the foundation pit,the displacement of the envelope structure only occurs at the top of the pile,the location where the maximum horizontal displacement occurs gradually moves to the lower part of the pile as the depth of precipitation excavation increases,and its extreme point finally appears at a position about one third from the bottom of the pile;The maximum point of building foundation settlement is closest to the edge of the foundation pit,and the settlement monitoring point of the building farther away from the foundation pit tends to uplift soon after excavation of the foundation pit.(3)Based on the fluid-solid coupling module of ABAQUS,the article established a three-dimensional finite element model considering the whole process of excavation.The entire simulation process is divided into six steps of precipitation and six steps of excavation,and each time the water level drops below the excavation surface by 0.5m.The numerical simulation results are compared with the measured data and theoretical calculations to verify the accuracy,and the deformation characteristics of the main structure caused by dynamic precipitation and excavation of the foundation pit were discussed in depth.For the deformation of the enclosure structure,the impact of precipitation in the first step is small,and the impact of precipitation in the second step is the most prominent,after the second step of precipitation,the impact of precipitation on the deformation of the enclosure structure is getting weaker and weaker,until the sixth step of precipitation,it played a positive role in the deformation of the enclosure structure and reduced the deformation to a certain extent;regarding the settlement of the surface around the pit,the surface settlement value caused by precipitation is less than that caused by excavation,among them,the fifth step of precipitation has the greatest impact on surface subsidence,and its settlement value has reached 14.2%of the total value of surface subsidence.(4)Through the numerical simulation,the basic laws of deformation of the foundation pit and surrounding environment under the influence factors of precipitation and non-precipitation,different precipitation methods,different precipitation speeds and depths,and different distances of buildings from the foundation pit are analyzed.Compared with the interlayer precipitation and the one-time precipitation method,the layer-by-layer precipitation method has less impact on the stability of the foundation pit itself and the surrounding environment;there is an optimal value for the speed and depth of the foundation pit precipitation,when the precipitation speed and depth reach the optimal value,it has a certain effect on the stability of the foundation pit;compared with the precipitation depth,the precipitation speed has little effect on the deformation of the foundation pit.更多还原