Research on the Dynamic Mechanical Response Characteristics of Foundation Pit Support Structures Under Loading and Unloading Conditions
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摘要: 基坑支护结构体系的变形和应力特征是评价基坑稳定性与安全性的重要指标。以广州新塘地铁站深基坑工程为研究对象,研究基坑-建筑交叉同步施工过程中支护结构的内力变化和变形规律。通过现场监测和动态数值模拟,分析了内支撑、地下连续墙、盖板等支撑结构在上盖建筑同步施工荷载、列车运营荷载、土方开挖卸载下的力学响应特征,探究了基坑整体变形规律和模式。研究表明:采用“M”荷载模拟列车动荷载,相较于正弦波荷载更加符合真实情况,模拟结果与实测数据基本一致;桩体深层水平位移分布呈现出“前倾型”“山丘型”和“纺锤型”三种模式。由于基坑明挖区和盖挖区交界处支护结构的转换,导致交界处出现应力集中现象,并且本项目复杂工况使得应力集中的位置在基坑转角处和地下连续墙中部之间转移。Abstract: The deformation and stress characteristics of foundation pit support structures are crucial indicators for assessing pit stability and safety. This study examined the internal forces and deformation of the support system during the simultaneous excavation and superstructure construction at the Guangzhou Xintang Metro Station deep excavation project. Through field monitoring and dynamic simulation, the mechanical responses of internal bracing, diaphragm walls, and slab covers to combined loads from superstructure construction, train operation, and earth excavation unloading were analyzed, and the pit’s overall deformation patterns were investigated. The results demonstrated that an “M”-shaped load pattern for simulating train dynamics better reflected real conditions compared to previous sinusoidal wave models, with simulations closely aligning with field measurements. Monitoring data analysis revealed three patterns in the horizontal displacement of the pile bodies: “forward-leaning”, “hill-type”, and “spindle-shaped”. Due to the transition in the support systems at the junction between the open-cut and cover-cut excavation sections, stress concentration occurred. Furthermore, the complex construction conditions of this project caused the location of stress concentration to shift between the corners of the pit and the midsections of the diaphragm walls.
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