Based on the engineering context of a shield tunnel section with ultra-shallow overburden along the coastal express line in a certain region, this study addresses the technical challenge of surface heave deformation during the construction of long-distance, large-section shield tunnels in shallow burial conditions. A numerical model for shield tunneling in complex underground environments with ultra-shallow overburden and large cross-sections was established using the software FLAC3D. Based on three different ground reinforcement conditions (no reinforcement, full-area reinforcement, and grid-type reinforcement), the control effect of grid-type ground reinforcement on surface deformation and heave during the shield tunneling process was systematically analyzed. The results show that: (1) The Z-direction displacement trends of the surface under the three conditions are consistent, with heave concentrated above the tunnel crown. Without cement-soil reinforcement, the surface heave increases significantly, with the maximum heave being approximately 52% higher than that of reinforced conditions, indicating that ground reinforcement measures are highly effective in controlling surface heave deformation; (2) Compared to full-area reinforcement, grid-type reinforcement reduces the reinforcement range by 22%, with only a 2% decrease in displacement. When the spacing between the cement-soil reinforcement layer and the tunnel bottom is 1 m, the heave increases by 6.5% compared to a spacing of 3 m, demonstrating that a larger spacing significantly enhances the reinforcement effect, and depth adjustment has a noticeable impact; (3) The scheme with a grid spacing of 4.65 m and a cement-soil layer bottom 2 m away from the tunnel bottom effectively controls surface heave, reduces cement usage, lowers construction costs and duration, and ensures tunnel safety and stability, providing a valuable reference for shield tunneling in shallow overburden sections. The research results can provide valuable references for controlling surface deformation during shield tunneling through ultra-shallow overburden sections.