A new gantry pile reinforcement scheme is proposed to handle the settlement issue of pre-existing tunnel caused by drilling and blasting tunnel excavation in the top. Three-dimensional loading and stratum structure model are established for the shield tunnel of Huiyan Expressway under the Ruyi Road Zhangbei Tunnel. We performed finit element simulation using ABAQUS to model the cyclic excavation construction process of the tunnel. The settlement patterns of the pre-existing tunnels in the top with and without gantry pile protection are studied. The results show that: 1) the gantry pile protection can effectively reduce the tunnel settlement caused by excavation in pre-existing tunnels. The maximum settlement of pre-existing tunnels is reduced by 2.49 mm when using gantry pile protection, which is 30% lower than that without protection. 2) The use of gantry pile protection increases the shear force and longitudinal axial force in the tunnel at connection of the crossbeam and the tunnel. The peak shear stress increases by 433.2 kN. The use of this technique requires local reinforcement of the connection to prevent local shear damage due to stress concentration in the tunnel.