Internal force and deformation response of the primary support in a large-section,biased double-track loess tunnel during earthquakes
The internal force and deformation characteristics of the primary support structure in bias double-track loess tunnels with large cross-sections in the Loess Plateau of Northwestern China under seismic loads were investigated.This study focuses on a biased double-track loess tunnel with a large cross-section in the Ningxia Hui Autonomous Region.The Kobe wave was se-lected as the seismic input using data from engineering geological surveys and design reports.A 3D numerical simulation model was established using the finite difference software FLAC3D.The dynamic response characteristics of the primary support structure were examined by analyzing its internal force and deformation under seismic loads.Results reveal that seismic loading induces changes in the tensioned side at the arch positions of the left and right tunnels.Moreover,varia-tions in the axial forces,alternating between tension and compression,were observed at the arch waist in the left tunnel and at the arch shoulder,arch foot,and inverted arch positions in the right tunnel.Under seismic loading,the peak bending moment and peak axial force for the left and right tunnels occur at the arch foot,indicating that the seismic design of this position should be strengthened.The bending moment distribution on the sidewalls of both tunnels is asymmetri-cal under static conditions,with this asymmetry being more pronounced in the left tunnel.Under seismic conditions,the maximum bending moment and axial force in the left and right tunnels oc-cur at the left and right arch foot,respectively.The left tunnel,being on the biased-pressure side,experiences a more intense dynamic response.The right tunnel exhibits greater overall de-formation than the left tunnel under static loading.When subjected to seismic loads,both tunnels experience increased deformation and tilt to the right.The maximum displacements occur at the right arch shoulder and right arch waist,with displacement values of 34.98 and 39.11 mm,re-spectively.Considering the analysis of structural internal force and deformation,the arch foot po-sition of both the left and right tunnels is vulnerable to structural damage under seismic load,with the left tunnel(biased-pressure side)being more prone to damage at the arch foot.
万方数据
维普
