ABSTRACT
The field monitoring and laboratory model test of segment were carried out to study the mechanical behavior of segments in construction of super large diameter shield tunnel in city. To obtain the soil pressure distribution and segment internal force under different loading conditions, the large-scale segment model test was carried out with the engineering structure loading platform which can apply regional load separately. It was found that the lateral pressure coefficient had a significant influence on the top earth pressure. With the increase of the lateral formation pressure, the bending moment and axial force of the top segment ring changed from positive to negative, and the values increased continuously. By comparing the segment failure characteristics in different loading soil layers, the internal force of the segments in the soft layer was significantly greater than that in the hard layer. The ring vertical deformation can be suppressed by the increase of lateral formation pressure, but the sectional deformation of the segment was still a transverse ellipse.In order to obtain the actual stress conditions of segments and surrounding rock, the field monitoring section was equipped with earth pressure boxes, steel bar gauges, concrete strain gauge and bolt axial force gauge. Due to the pressure of the synchronous grouting, the monitoring pressure was slightly higher than the calculated earth pressure. The rebar of the segments had a high safety redundancy, so it was suggested to reduce the reinforcement ratio properly to be more economical. It was also found that the axial force of the axial bolt is significantly greater than that of the circumferential bolt.
