Optimization of advanced support parameters is a core issue in controlling surrounding rock stability during the construction of ultra-large cross-section tunnels. Taking a single-bore four-lane tunnel in the Shenzhen-Shanwei special cooperation zone as the background, this study systematically investigates the influence of key parameters such as the thickness of the grouted reinforcement layer, the length of small pipes, the outer pipe angle, diameter, and circumferential spacing on the evolution of surrounding rock displacement through numerical simulation and field monitoring. The results indicate that the thickness of the grouted reinforcement layer and the structural parameters of small pipes significantly affect the distribution of surrounding rock displacement fields, with an influence amplitude of 1.3% to 16.3%, demonstrating substantial regulatory effects. When the pipe length is 4.5 m, the support effect is optimal, and surrounding rock displacement exhibits nonlinear reduction. With an optimal outer plug angle of 10° and a circumferential spacing of 0.4 m, a synergistic support system can be formed, achieving the best balance between reinforcement in fractured zones and pipe stress. Field monitoring verification confirms that the optimized support scheme effectively controls vault settlement and invert uplift, significantly reduces surrounding rock deformation, and enhances both construction safety and efficiency while delivering favorable economic and social benefits.