Stress characteristics and weakening analysis of T-joint of connection passage by mechanical excavation method

The forces on the T-joint parts of connection passage by the mechanical excavation method is complex, and their safety problems are severe. A kind of connection massage segment and a portal structure are proposed. The numerical model for the T-joint of connection passage by the mechanical excavation method is established using the ANSYS finite element software. The deformation and stress of the tunnel with portal structures with different strengths at the buried depth of 15 m are analyzed. The results show that with the decrease of the strength of the portal structures, the maximum displacement of the tunnel and the displacement of the segment increase, and the maximum stress of the tunnel increases, but the increase amplitunde is slight. After the opening of the segment, the displacements of the segment above and below the centre of the opening are the most dangerous and need to be reinforced. The bolts mainly bear the stress at the joint, and special attention should be paid to the safety of the bolt connection between the hole segments. The research conclusions may provide a reference for designing and safely constructing the connection passage by the mechanical excavation mehtod.