Analysis on Asymmetric Excavation and Asymmetric Support Design System of Adjacent Tunnel Foundation Pit

New foundation pits in densely populated urban areas often face the dual constraints of "narrow site and proximity to subway tunnels". Traditional symmetrical support and symmetrical excavation can easily cause excessive lateral displacement of the tunnel, endangering operational safety. It is urgent to reveal the horizontal displacement response law of tunnels under the coupling of asymmetric support and asymmetric excavation, and propose a new design and construction method that balances economy and safety. This article takes a nearby tunnel foundation pit project in Guangzhou as an example to propose the design principle of asymmetric support structure for the foundation pit and the construction method of asymmetric excavation. Using Lizheng software and finite element simulation method, a structural deformation model that can simulate the actual asymmetric support and excavation process is established. The research results indicate that the error between numerical simulation and actual monitoring results is only about 7%, and the displacement control rate has increased by 1.2 times compared to conventional methods. This study not only solves the stability and safety issues of subway tunnels, but also proves that relevant design concepts have a good protective effect on tunnels in complex environments, providing a good reference for the design of similar foundation pit support.