地铁车站复合墙结构体系受力特性

针对地铁车站复合墙体系受力变形规律与理论计算结果存在较大差异,围护结构土压力分布规律和主体结构内力具有不确知性的问题,采用EPS板(聚苯乙烯泡沫)代替防水垫层进行模型试验和数值模拟,对比分析复合墙和叠合墙体系受力、变形特性,得到墙后水平土压力、周围地表沉降、结构体系内力等变化规律。结果表明:复合墙技术具有良好的卸荷作用,可有效改善地铁车站主体结构受力状态;卸荷效果随EPS板厚度增大或弹性模量减小而增强,但地连墙弯矩会随着卸荷作用的增大而增大,因此,并非EPS板厚度增大或弹性模量越小就越好,而是需要确定合理的减载参数;复合墙体系会引起较叠合墙体系更大的周围地表沉降,本文条件下的主要影响区域为0.60H～1.25H(H为基坑深度),沉降差约为12%。

Mechanical characteristics of compound wall structural system for subway station

The stress states and deformation laws of the compound wall system of subway stations are quite different from theoretical calculation results, and the distribution law of earth pressure on retaining structure and the internal force of the station structure are uncertain. In this study, expanded polystyrene (EPS) foam was used to replace waterproof layer, and model tests and numerical simulations were conducted to investigate the stress states and deformation laws of compound wall and composite wall systems. The horizontal earth pressure behind the diaphragm wall, the surrounding ground surface settlement, and the structural internal force were obtained. Research results show that the compound wall technique had good load reduction effect and could effectively improve the stress state of the main structure of the subway station. The load reduction effect of the compound wall technique increased with the increase in the thickness of the EPS board or the decrease in the elastic modulus of the EPS board. However, the bending moment of the diaphragm wall would increase with the increase in the load reduction effect of the subway station structure. Thus, the load reduction effect is not always available at a higher EPS board thickness or a lower elastic modulus, but reasonable load reduction parameters of EPS board are required. The compound wall technique could induce a larger surrounding ground surface settlement than the composite wall technique. The influence area of ground surface settlement was about 0.60H to 1.25H in this study (H is the depth of the foundation pit), and the difference of the settlement between the two techniques was about 12%.