Mechanical behavior of segment rebar of shield tunnel in construction stage

In this paper, a 3D finite element (FE) program ADINA was applied to analyzing a tunnel with 9 segment rings. The loads acting on these segment rings included the squeezing action of tail brush of shield machine under attitude deflection, the jacking forces, the grouting pressure and the soil pressure. The analyses focused on the rebar stress in two statuses: (1) normal construction status without shield machine squeezing; (2) squeezing action induced by shield machine under attitude deflection. The analyses indicated that the rebar stress was evidently affected by the construction loads. In different construction status, the rebar stress ranges from -80 MPa to 50 MPa, and the rebar is in elastic status. Even some cracks appear on segments, the stress of segment rebar is still at a low level. It is helpful to incorporate a certain quantity of steel fiber to improve the anti-crack and shock resistance performance.