Dynamic response characteristics of shallow-buried biased small clearance tunnel subjected to various ground shaking

The axial force and bending moment of tunnel lining are crucial for lining stability. To investigate the response patterns of axial force and bending moment in shallow-buried biased small clearance tunnels under various conditions – including different adjacent slope angles, loading wave types, peak loads, and loading directions – extensive numerical simulations were conducted. The numerical results were subsequently verified through large-scale vibration table physical model experiments. The findings reveal that the variation patterns of lining axial force and bending moment under bidirectional coupled seismic waves demonstrate similarity to those under vertical seismic waves. Vertical seismic motion exerts a more pronounced influence on lining axial force response. Seismic wave peak intensity significantly affects lining axial force and bending moment, with both parameters showing gradual increases corresponding to peak load escalation. The arch shoulder of the slope-side right tunnel lining exhibits particularly strong axial force and bending moment responses. While Darui wave, Wenchuan wave, and Kobe wave produce essentially consistent axial force and bending moment response patterns in tunnel linings, their magnitudes differ substantially. Seismic wave type primarily influences response magnitude rather than characteristic patterns of axial force distribution. Increasing slope angles adjacent to tunnels correlate with heightened axial force and bending moment responses in linings. A logarithmic functional relationship exists between slope angle and response values at the lining arch shoulder. These findings provide valuable references for seismic design of shallow-buried biased small clearance tunnels.