现代基坑工程中出现坑中坑的情况越来越普遍，设计需要对坑中坑的桩墙围护进行结构分析。坑中坑的外围基坑与内部基坑的桩墙存在相互影响，因此，坑中坑的桩墙围护结构受力分析相对而言更加复杂。针对这种坑中坑内、外桩墙的复杂受力情况，提出了坑中坑桩墙围护结构的弹性支点法联合求解模型，通过对内、外桩墙间有限土体的地基弹簧刚度的求解，使该模型可以解决坑中坑桩墙的内力变形计算问题。具体的坑中坑工程实例分析表明，采用弹性支点法联合求解模型得到的围护结构变形、内力与工程实际比较吻合，研究成果具有一定理论与工程实用意义。

In the modern foundation pit engineering, pits-in-pits is becoming more and more popular. It needs special analysis according to the structural design requirements of retaining walls. There exists mutual influence between the outer retaining walls and the inner retaining walls; so the stress analysis of the retaining walls is more complicated. For the complex stress condition of the outer and the inner retaining walls in pits-in-pits, a combined bars FEM system based on the flexibility fulcrum method is developed. By solving the spring stiffness of the finite soil mass between the inner and outer retaining walls, the model can be used to solve the problem of calculating the internal force and deformation of the retaining wall. The pits-in-pits case study shows that the deformation and internal force of the retaining structure calculated by flexibility fulcrum method are quite consistent with the engineering practice. The research results have certain theoretical and engineering practical significance.