Study on Seepage and Deformation Responses during Tunnel Excavation and the Influence of Support Parameters
To investigate the evolution characteristics of groundwater seepage and surrounding rock deformation during tunnel excavation and the effectiveness of support control, a steady-state seepage model and an elastoplastic mechanical model were developed for a deep-buried circular tunnel. The spatial distributions of the seepage and displacement fields and their responses to construction steps under the bench excavation method were analyzed, and the effects of the thickness, elastic modulus, and permeability coefficient of the primary support and grouting ring were examined. The results indicate that after excavation, groundwater converges toward the tunnel cavity and tunnel face, while the surrounding rock deforms toward the excavated space; the more significant responses are mainly concentrated around the tunnel periphery and near the tunnel face. As the excavation face approaches and passes the studied section, the peripheral displacement and outflow change rapidly and then gradually stabilize. Increasing the thickness of the primary support and grouting ring reduces the peripheral displacement and water inflow, but the incremental control effect diminishes with increasing thickness. Increasing the elastic modulus of the primary support and grouting reinforcement zone is beneficial for controlling surrounding rock deformation, whereas reducing their permeability coefficients can effectively decrease tunnel water inflow. When the water-blocking capacity of the primary support is enhanced, the external water pressure on the lining increases; when the water-blocking capacity of the grouting ring is enhanced, the external water pressure on the lining decreases. These results can provide a reference for selecting support and grouting parameters for tunnels in water-rich surrounding rock.
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