Experimental study on buckling behavior of corrugated steel arch support under tunnel surrounding rock pressure

Steel arch supports are widely used in tunnel construction, but their thin-walled nature makes them susceptible to buckling prior to strength failure. To investigate the evolution of buckling behavior and the spatial characteristics of deformation, physical model tests were conducted on steel arches. Two models were considered: flat steel arches and corrugated steel arches, along with two surrounding rock conditions: with or without sand filling. By analyzing the buckling deformations, strain and critical loads, the results demonstrated that the corrugation shape dramatically enhances structural stability, increasing the critical buckling load by approximately 20 times under identical sand-filled conditions, while reducing vault settlement by approximately 80% compared with flat steel arches. Lateral pressure from the surrounding rock further improves stability, with a lateral pressure coefficient of 0.7 yielding a 145.6% increase in the critical buckling load relative to the no-lateral-pressure condition. The results further revealed that the buckling evolution of the steel arch undergoes three stages: the elastic stage, the nonlinear plastic stage and the instability stage, where the plastic stage is dominated by tangential strain, with magnitude 1.5 to 3 times that of the longitudinal strain. Spatial differentiation of buckling deformation is identified: at the wave-peak, the vault flattens under compression, while at the wave trough, the haunch bulges outward. This study has revealed the evolutionary stages and spatial distribution of buckling in steel arches, and has identified critical early-warning indicators. The results provide practical references for both construction-stage stability control and long-term in-service safety monitoring.