Abstract:

The definition of early stress form of inverted arch when simultaneously excavated with lower bench and related control standards are very important. Hence, the early stress of inverted arch of Zhongtiaoshan Tunnel under the effect of external load is analyzed by numerical analysis, displacementload inversion method, etc. The lower bench is simultaneously excavated with inverted arch, and due to the particularities of the method, the inverted arch will bear the load of surrounding rock deformation, excavation machine and cover soil weight after 2 hours of inverted arch construction. The analytical results show that the surrounding rock deformation greatly affects the stress on inverted arch; and the maximum compression stress induced by surrounding rock deformation occurs on inverted arch feet, while the weights of cover soil and excavation machine will reduce the compression stress on arch feet and increase the compression stress on crown bottom. The distribution of compression stress on crown top shows a Wshape, and the maximum compression stress of 0.14 MPa occurs on crown bottom. The compression strength control standard could be 0.2 MPa after 2 hours of inverted arch construction considering safety stock. The comparison results between the abovementioned method and traditional one show that the using of early highstrength concrete for inverted arch construction is necessary.

Key words: Zhongtiaoshan tunnel, bench method, inverted arch, railway tunnel, surrounding rock deformation