北京地铁新宫站基坑复合支护过渡部位的冗余度设计

Research on redundancy design of the transition section of composite pit support in the foundation pit of the Xingong Station of the Beijing subway

复合支护结构过渡部位中两种支护结构的水平刚度、受力方式、作用机理有所差异,故过渡部分是基坑安全控制的关键部位,对过渡部分进行冗余度的研究和优化具有非常实际的工程意义。论文结合北京地铁19号线新宫站基坑工程实例,通过数值模拟的方法,釆用MIDAS/GTS软件实现基坑的施工全过程模拟。在假定复合支护结构部分失效的情况下,以结构变形与受力情况为标准,对复合支护结构的冗余度进行了计算和优化设计。结果表明:(1)在出现支护结构局部破坏的情况下,复合支护体系的过渡部位桩体变形都出现了明显的增大;在有腰梁的情况下,桩体的变形得到了很好的控制;(2)出现局部破坏后,结构加入腰梁,增加了结构的传力路径,使整个结构的内力重分布更加均匀合理,可以有效地防止应力的集中,保证了结构的安全稳定;(3)在两种失效模式下,在支护结构之中加入腰梁对结构的冗余度都有明显的提升;混凝土腰梁对结构冗余度的优化效果要比钢腰梁好一些。在实际工程中,腰梁的加入对提升支护结构的稳定性和冗余度有着重要的意义,应注重对腰梁的设计应用。

Numerical simulation methods are used to simulate the whole process of construction of the foundation pit in the foundation pit project of the Xingong Station of Beijing Metro Line 19.Under the assumption that the composite support structure partially fails,the structural deformation and force conditions are taken as the criteria,and the redundancy of the composite support structure is calculated and optimized.The results show that(1) in the case of partial destruction of the supporting structure,the deformation of the piles at the transition section of the composite support system increases significantly;in the case of the waist beam,the deformation of the pile is well controlled.(2) After the partial damage occurs,the structure joins the waist beam,which increases the force transmission path of the structure,and the internal force redistribution of the entire structure is more uniform and reasonable,which can effectively prevent the stress concentration and ensure the safety and stability of the structure;(3) In the two failure modes,adding the waist beam to the support structure significant increases the structural redundancy,and the effect of theconcrete waist beam on the structural redundancy is better than that of the steel waist beam.In practical projects,the addition of waist beam is of important significance in improving the stability and redundancy of support structures,and the design and application of the waist beam should be emphasized.