Abstract: For the deep and large foundation pit adjacent to the subway, the pit construction method needs to be adopted in order to ensure the safety of the pit and the surrounding structures and utilities. To solve the problem of slow construction progress induced by the divisional excavation, combined with an engineering example, the support replacement condition of a deep foundation pit adjacent to the subway is optimized. Throughout review, evaluation and analysis, the results show that the safety envelope still meets the requirements, and the impact on the surrounding environment is manageable. Subsequently, the coupling design of different working conditions can be carried out in advance according to the actual needs of the site, so as to achieve the multi-dimensional optimization of the excavation sequence of adjacent zones. While ensuring the self-safety and environmental safety of the foundation pit, the construction speed of the foundation pit can be accelerated to the greatest extent and better economic benefits can be achieved. 

Key words: deep and large foundation pit, divisional excavation, middle partition wall, change of support