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在FLAC3D中,采用梁单元模拟基坑钢支撑时,现有的预应力施加模拟方法是在梁单元设置以后,通过对梁单元两端的节点施加一对相反的作用力来代表要施加的预应力,导致支撑预应力变为围护体系的外力这一与实际不符的情况发生。为此,本文根据钢支撑与围护结构相互作用的机理,提出一种改进的钢支撑预应力施加模拟方法—虚拟位移法,即先固定梁单元一端节点,另一端节点施加节点虚拟位移,虚拟位移再施加于梁单元上,使梁单元压缩形成预应力。以深圳地铁5号线前海湾站基坑工程为背景,进行了常规方法和虚拟位移法的比较:在对支撑结构的影响上,常规方法引起各道支撑的轴力变化与实际存在明显的差别,而虚拟位移法则与实际一致。本文工作有实际意义。
In FLAC3D, when beam elements are used to simulate the steel support of foundation pit, the existing simulation method of prestressing is to set the beam element to be opposite by applying a pair of opposite forces to the nodes at both ends of the beam element to represent the prestress to be applied , Resulting in supporting the prestress into a system of external force and the actual situation does not match. Therefore, based on the mechanism of the interaction between the steel support and the retaining structure, this paper proposes an improved method of virtual prestressing of the steel support, which is to first fix one end node of the beam element and apply the virtual displacement of the node to the other end node, Displacement is applied to the beam element to compress the beam element to form the prestressing force. Taking the construction of Qianhaiwan Station foundation pit project of Shenzhen Metro Line 5 as a background, the comparison between the conventional method and the virtual displacement method is made. The influence of the conventional method on the support structure is obviously different from the actual one , While the law of virtual displacement is consistent with the actual. This work has practical significance.