Abstract: In traditional support design, excessive safety redundancy often leads to resource wastage and increased costs. Here, the counteracting soil in support design is optimized to enhance the safety and economy of support structures while avoiding unnecessary overprotection, thereby achieving efficient resource utilization. A case study is conducted on a metro station foundation pit project in Hohhot, China, and the control effect of support structures on the foundation pit deformation during construction is systematically analyzed based on field monitoring data and numerical simulation methods. This study focuses on the effects of the height and length of counteracting soil on the foundation pit deformation. An optimization analysis of the counteracting soil is performed while maintaining consistent steel support parameters. Through optimization analysis of different counteracting soil parameters (such as length and height), it is found that the height and length of counteracting soil substantially influence the maximum horizontal deformation of the metro station. Specifically, the horizontal deformation gradually decreases as the height and length of the counteracting soil increase, and vice versa. Based on these findings, an optimized counteracting soil parameter selection scheme—height and length greater than 7 and 80 m, respectively—is proposed. This scheme maintains the metro station deformation within the safety range, thereby meeting the projects safety and economic requirements. Moreover, the rationality of adjusting the counteracting soil parameters at different construction stages is explored. 

Key words: deep foundation pit, counteracting soil, adjacent metro station, numerical simulation, support scheme optimization