Resurvey and stability analysis of urban rail transit elevation control network affected by rainstorm

The stability of the elevation control network is the key to ensuring the correct construction of urban rail transit projects according to the design scheme. Due to the long construction period of urban rail transit projects, the ground elevation control network is vulnerable to instability and destruction caused by urban development and its engineering construction. Regular repetition surveys are required to ensure accuracy and stability. In addition, when the external environment changes suddenly, it is necessary to encrypt and retest the elevation control network in time, such as the potential impact of Zhengzhou 7-20 rainstorm on ground elevation control points. To clarify the changing trend and potential reasons of the subway elevation network, this study takes the elevation control network of Zhengzhou Metro Line 8 as an example. This paper first introduces the layout method, repetition survey principle, technical measurement requirements, and the stability analysis method of the starting point and results update standard. Secondly, the potential causes of the change of the subway elevation control network caused by rainstorms and the influence of regional settlement on the subway elevation control network are preliminarily analyzed by using the extra repetition survey results and conventional repetition survey results. Finally, the solution to the influence of regional settlement on the subway is proposed. The results show that: 1. Using the method of combined elevation difference can judge whether the starting point is stable; 2. ±5mm as the result update margin is reasonable; 3. It is appropriate to adopt the countermeasures of “ensure an error is controllable in the process and one-time adjustment after interval penetration” in the construction of the subway, and it is an effective means to control the influence of settlement for the operation of subway to control the surrounding groundwater exploitation.