Abstract:

The Badaling Great Wall Station on BeijingZhangjiakou Highspeed Railway is an underground mined station, of which the transition section is designed as a single span with a maximum excavation span of 32.7 m and a maximum excavation area of 497 m2. The surrounding rock of superlarge crosssection tunnel is always characterized by large deformation and instability, the largescale mechanical construction cannot be applied to multiguide pilot excavation, the construction speed is low, and the prestressed anchorage cable in tunnel is difficult to be carried out. Hence, the so called DFHZ method, advanced excavation of tunnel top, layered downward excavation, core soil reserved and keys locking, is adopted, and the advantages of construction flowchart of the method are introduced. By adopting the abovementioned method, the tunnel safety can be guaranteed, the deformation and settlement of the surrounding rock can be reduced, and the mechanical construction is available. The stability of the surrounding rock can be guaranteed by using prestressed anchor rod and prestressed anchorage cable. During the construction of prestressed anchorage cable, the technologies, i.e. adding anchoring joints, setting up slurry with sulphoaluminate cement, free section grouting and then anchoring section, and highpressure grouting, etc.〖KG-*3〗, are adopted to shorten the construction schedule of anchorage cable and guarantee its safety. The monitoring results of crown top settlement and horizontal convergence at Zhangjiakou End are small, which indicates the rationality of the abovementioned method.

Key words: highspeed railway, mine station, superlarge crosssection, DFHZ method, prestressed anchorage cable, prestressed anchor rod