Abstract: Tunnels in soft rock mass with large deformation are characterized by low strength, significant deformation, and poor stability. During the construction, safety hazards such as large deformations, collapses, and sudden water or mud inflows are likely to occur. These hazards pose serious threats to both the construction safety and the engineering quality. Although researchers both domestically and internationally have conducted extensive studies on the optimization of support parameters, selection of construction methods, and deformation control, the dynamic optimization of support parameters and construction methods remains an impressive technical challenge under complex geological conditions. This study focuses on a tunnel in soft rock mass with large deformation in an expressway, utilizing on-site monitoring data and numerical simulation analysis to optimize the tunnel’s support parameters and construction methods. By analyzing the deformation characteristics of the surrounding rock and the stress behavior of the support structure, recommendations are made to optimize the support parameters for arch support, side wall support, and local weak sections. Additionally, based on the applicability analysis of various construction methods, the CRD method is recommended as the optimal construction approach under complex geological conditions. Suggestions for dynamically adjusting support parameters and construction methods are also provided. The research results demonstrate that the optimized support parameters and construction methods effectively control the deformation of surrounding rock, significantly enhancing the safety and quality of tunnel construction. These findings provide a theoretical foundation and practical guidance for optimizing support parameters and selecting construction methods in tunnel engineering under similar complex geological conditions, offering substantial significance for advancing tunnel construction technology.

Key words: Soft Rock, Numerical Analysis, Tunnel, Construction Method, Surrounding Rock Deformation