The platform of the Badaling Great Wall Underground Station consisted of large span triple tunnels. The triple tunnels passed through several major faults. Based on preliminary in situ monitoring, the interaction behavior among triple tunnels was significantly severe, and the original supports failed to meet the safety requirement. Therefore, pipe roof pre-support (PRPS) and curtain grouting pre-reinforcement (CGPR) were used as the pre-construction techniques. By numerical investigation, the pipe diameter, the arrangement angle of PRPS, and the grouting thickness of CGPR were optimized as 108 mm, 150°, and 3 m, respectively. According to numerical results, PRPS predominantly bore loose rock and reduced mean crown settlement (MCS), while CGPR primarily improved the mechanical properties of rock and decreased the pillar plastic ratio (PPR). PRPS and CGPR had complementary advantages in time, space, and mechanical properties. PRPS could timely form a strong arch structure far ahead of the tunnel face, CGPR could effectively restrict the development of plastic zone. They mutually and actively formed a strong permanent ring in front of the tunnel face. After the field application of PRPS and CGPR, the mean surrounding rock pressure reduced by 33.4%, the MCS reduced by 58.7%, and no support damage was observed. The excavation safety was guaranteed.

Compared with single or twin tunnels, the pressure arch effect of deeply buried, symmetrically distributed triple tunnels are more complex and less studied. In this paper, the arching responses are in-situ measured in the deeply buried, symmetrically distributed triple tunnels of Badaling Great Wall station. Numerical research is subsequently conducted to investigate the formation and development of the pressure arch of triple tunnels. Then, the influencing law of buried depth on pressure arch behavior is systematically studied. Based on monitoring data, the rock pressure distribution is asymmetric about the axis of the triple tunnels, and the arching response of the middle tunnels is more significant than that of the left and right tunnels. According to numerical analysis, a combined large pressure arch may be easily formed across the triple tunnels. The pre-arching and double-arching effects are also numerically observed during triple tunnel excavations. The inner boundary of the pressure arch of the middle tunnel is 14.0 m, nearly two times higher than those of the left and right tunnels. This simulation result indicates that the mechanical state of the middle tunnel is the least desirable. Moreover, the critical arching depth of closely spaced tunnels is 1.75 times that of a single tunnel. Compared with a single tunnel, the support of triple tunnels should be additionally strengthened.