基坑工程装配式钢管混凝土内支撑体系设计方法

摘要

Centered on the characteristics of deep excavation engineering for open-cut subway station projects, a fabricated inner-bracing system of concrete-filled steel tube, which consisted of normal straight components, short components, connection joints, etc. , was developed. Based on the features of inner-bracing stress and structure, the internal force calculation formulas were derived from all the components. Referring to the specifications of concrete-filled steel tube and the formulas of column stability, several calculation methods of bearing capacity for the supports and ring-shape purlin were proposed. The mix proportion of filled concrete was designed, and the concrete physical, working and mechanics properties were detected by material tests, and then the lightweight, slight expansion and self-compacting concrete were prepared as the inner-bracing filling material. Taking a deep excavation engineering of a station project in Beijing Subway as a case, the inner-bracing system of normal section foundation pit was designed and studied. The results show that the calculation methods of inner-bracing system design is reasonable and reliable, and the designed inner-bracing system meet the requirements of excavation support force and foundation pit stability.%为了解决常用基坑内支撑刚度不足、拆装不便等问题，针对明挖地铁车站基坑工程特点提出装配式钢管混凝土内支撑体系，包括标准直撑、短接直撑及连接节点等。根据该支撑体系受力和结构特点，推导了各组成部分的内力计算公式；依据钢管混凝土规范和压杆稳定欧拉公式，建立了钢管混凝土支撑、围檩等部件的承载力计算方法；通过混凝土材料的配合比设计及工作、物理、力学性能检测试验，配制出了具有轻质、微膨胀和自密实性能的CL50高强混凝土作为钢管混凝土内支撑的填充材料；以北京地铁某车站基坑工程设计资料为依据，对其标准段进行了详细的支撑体系设计，并对基坑变形、稳定性和支撑受力进行了验算。研究结果表明：所提出的内支撑体系设计计算方法合理可靠，所设计的装配式钢管混凝土内支撑体系能满足该基坑工程内支撑体系受力和基坑稳定的要求。