昆明湖沼相软土地区深基坑支护及数值模拟研究

发布时间：2018-08-11 11:59

【摘要】：随着我国城市化高速发展,城市地下空间的开挖和利用成为城市基建的热点,在城市建设过程中正遇到越来越多的深基坑工程。在具体实际施工过程中,往往因为缺乏正确的设计或精准的施工,容易诱发严重事故,甚至造成人员的伤亡以及巨大的经济损失。而昆明地区软土成因复杂,工程地质特性较为特殊,与我国目前采用的以沿海地区为主要依据建立的国家标准差别较大,因此对于昆明湖沼相软土地区深基坑变形特点研究具有重要科研意义。本文研究的对象是昆明软土区某深基坑工程,使用的研究方法包括了现场检测、非线性有限元和理论法等,研究了以排桩+环形内支撑等多种联合方案下深基坑支护结构的变形、内力等规律,支护结构厚度和嵌固深度等因素对稳定性的影响,为实际工程项目作借鉴和参考。本文的主要研究内容如下:(1)分析了昆明湖沼相软土分布规律和工程地质特征,针对昆明湖沼相软土区某基坑工程特点,提出了以排桩、环形内支撑、坡面喷锚网等多种手段,结合坡顶大面积卸土减载的基坑支护方案,该方案在昆明湖沼相软土区基坑工程中首次运用,具有技术可靠,施工便利安全的特点。(2)针对昆明典型软土区建设场地深基坑的工程地质条件,确定了该深基坑监测内容、相应监测点、设计方案及细节方面的内容,对具体基坑的工程监测数据加以综合分析,从而获得该施工环境下的支护结构变形以及内力的动态规律等。(3)运用有限元分析法,基于MIDAS/GTS软件系统构建本工程的模型,对涉及到的相关施工工况进行模拟,将具体的模拟结果和实际监测的结果进行对比分析。最终发现两者基本一致,说明本次模型具有科学可行性。对应的结果:随着基坑深度的增加,相应内支撑被构建,侧向位移最大值开始呈现下移趋势,支护结构位移曲线也由悬臂式型位移逐渐呈现出抛物型位移曲线。(4)利用该数值模型,进一步研究了围护墙的厚度,以及对应的嵌固深度对支护结构稳定性所产生的影响。对应的结果:这两个参量在增加后,围护结构的变形减小,当两个参量达到一个临界值后,防范变形的效果基本上没有变化,成本开始大量增加。表明在满足结构要求时还需考虑造价。
[Abstract]:With the rapid development of urbanization in China, the excavation and utilization of urban underground space has become a hot spot in urban infrastructure, and more deep foundation pit projects are being encountered in the process of urban construction. In the actual construction process, due to the lack of correct design or accurate construction, it is easy to induce serious accidents, and even cause casualties and huge economic losses. However, the origin of soft soil in Kunming area is complex and the engineering geological characteristics are special, which is quite different from the national standard established mainly on the basis of coastal area in our country. Therefore, it is of great significance to study the deformation characteristics of deep foundation pit in the soft soil area of lake and marsh in Kunming. The research object of this paper is a deep foundation pit project in the soft soil area of Kunming. The research methods used include field detection, nonlinear finite element method and theoretical method, etc. In this paper, the influence of deformation, internal force and other factors on the stability of deep foundation pit supporting structure, such as the thickness of supporting structure and the depth of embedded structure, is studied under the combined schemes of ring and inner bracing of piles, which can be used for reference and reference for practical engineering projects. The main research contents of this paper are as follows: (1) the distribution law and engineering geological characteristics of soft soil in Kunming lake and marsh facies are analyzed. According to the engineering characteristics of a foundation pit in Kunming lake and marsh facies soft soil area, several methods are put forward, such as pile row, annular support, shotcrete anchor net on slope, etc. Combined with the foundation pit support scheme with large area unloading and load reduction on the top of slope, the scheme is first applied in the foundation pit engineering of Kunming Lake and soft soil area, and it is technically reliable. (2) in view of the engineering geological conditions of the deep foundation pit in Kunming typical soft soil area, the monitoring contents, corresponding monitoring points, design scheme and details of the deep foundation pit are determined. The monitoring data of concrete foundation pit are synthetically analyzed to obtain the deformation of supporting structure and the dynamic law of internal force in the construction environment. (3) the model of this project is constructed based on MIDAS/GTS software system by using finite element analysis method. The related construction conditions are simulated, and the concrete simulation results and the actual monitoring results are compared and analyzed. Finally, it is found that the two models are basically consistent, indicating the scientific feasibility of this model. The corresponding results: with the increase of foundation pit depth, the corresponding inner braces were constructed, and the maximum lateral displacement began to show a downward trend. The displacement curve of supporting structure is also gradually showing parabolic displacement curve from cantilever displacement. (4) by using the numerical model, the influence of the thickness of the retaining wall and the corresponding embedded depth on the stability of the supporting structure is further studied. The corresponding results are as follows: after the increase of these two parameters, the deformation of the envelope structure decreases. When the two parameters reach a critical value, the effect of preventing deformation basically remains unchanged, and the cost begins to increase greatly. It is indicated that the cost should be taken into account when meeting the structural requirements.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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