昆明某环境复杂闲置基坑长期变形分析与控制

发布时间：2018-11-13 09:20

【摘要】：随着我国城市化进程的不断深入推进,城市地下空间得到空前开发,基坑工程大量涌现。基坑施工会打破场地初始应力平衡状态,引发围护结构变形、地表沉降和周边土体发生位移,对周边环境造成不利影响。基坑支护作为临时性支撑结构,其设计使用年限一般较短。但工程建设可能会因资金短缺和设计变更等而出现长时间停工,形成闲置基坑。由于土体蠕变、湿化作用、降水固结和混凝土徐变等因素,使得基坑随着闲置时间的增长而变形加大,即基坑变形具有时间效应。时间效应会加剧基坑工程对周边环境安全的潜在威胁。本文以昆明某环境复杂闲置内支撑深大基坑为研究对象,通过三维数值模拟分析基坑的长期变形,根据模型分析和现场调查结果,进而提出基坑变形控制措施,最后采用数值方法分析加固效果。主要研究内容如下:(1)建立基坑、地下连续墙和地铁结构三维整体数值模型,分析基坑开挖过程中围护结构、区间盾构遂道、地铁车站,存车线结构的受力变形情况,通过比较模型计算结果和现场监测数据,验证所建模型的可靠性。(2)从土体蠕变、湿化作用、降水固结,混凝土徐变等方面,分析基坑长期变形的影响因素和作用机理,进而建立模型分析所需土体及钢筋混凝土支撑强度参数的简化方法。(3)通过试验方法获得基坑闲置后土体及支撑结构的强度参数,采用有限元方法建立考虑时间效应的整体时变模型,对基坑闲置前后整个开挖过程进行三维数值模拟,将计算结果与不考虑时间效应的非时变模型分析结果进行比较,分析基坑长期变形特性及对周边地铁结构受力变形的影响。(4)基于时变模型计算结果,结合闲置期间对基坑自身及周边环境潜在安全风险的分析,提出基坑长期变形控制措施,并分析了加固措施的可靠性。
[Abstract]:With the development of urbanization in China, urban underground space has been developed unprecedentedly, and foundation pit engineering has emerged in large numbers. The foundation pit construction will break the initial stress equilibrium state of the site, cause the deformation of the enclosure structure, the surface settlement and the displacement of the surrounding soil, which will have a negative impact on the surrounding environment. As a temporary supporting structure, the design life of foundation pit support is generally short. But the construction may be stopped for a long time due to the shortage of funds and design changes, forming idle foundation pit. As a result of soil creep, humidification, dewatering and consolidation, concrete creep and other factors, the foundation pit deformation increases with the increase of idle time, that is, the foundation pit deformation has a time effect. The time effect will aggravate the potential threat to the surrounding environment safety caused by foundation pit engineering. In this paper, a deep and large foundation pit with complex idle inner braces in Kunming is taken as the research object. The long-term deformation of the foundation pit is analyzed by three-dimensional numerical simulation. According to the results of model analysis and field investigation, the deformation control measures of foundation pit are put forward. Finally, numerical method is used to analyze the reinforcement effect. The main research contents are as follows: (1) the three-dimensional numerical model of foundation pit, underground continuous wall and subway structure is established. The reliability of the model is verified by comparing the results of model calculation and field monitoring data. (2) from the aspects of soil creep, humidification, dewatering and consolidation, concrete creep, the influencing factors and mechanism of long-term deformation of foundation pit are analyzed. Then a simplified method for analyzing the required soil mass and reinforced concrete bracing strength parameters is established. (3) the strength parameters of the soil and bracing structure after foundation pit is idle are obtained by the test method. A global time-varying model considering time effect is established by using finite element method. The whole excavation process before and after foundation pit idling is simulated by three-dimensional numerical simulation. The results are compared with the results of time-invariant model without time effect. The long-term deformation characteristics of foundation pit and its influence on the deformation of surrounding subway structure are analyzed. (4) based on the results of time-varying model, the potential safety risk of foundation pit itself and surrounding environment during idle period is analyzed. The long-term deformation control measures of foundation pit are put forward and the reliability of reinforcement measures is analyzed.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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