Abstract:

A numerical model which was verified previously by field measurements was used in this study to investigate the deformation behavior of tunnel intersection during the excavation of connection adit. Parametric studies were conducted by using different cover depths, rock mass strengths, and lateral stress coefficients. Results of the numerical analyses show that the deformation mechanism of the intersection during the connection adit excavation depends on plastic zone distribution and the direction and the magnitude of the principal stress. For elastic model, the deformation of the main tunnel on the connection adit side would move towards the excavation direction of the connection adit. For elastoplastic model, the deformation behavior of the main tunnel would be influenced by the magnitude and orientation of the principal stress. According to the results of this paper, the deformation mechanism of tunnel intersection is influenced both by the release of the lateral constraint due to connection adit excavation and the loading changes due to the plastic zone.