Experimental and numerical study of the failure mechanism and stability of tunnel linings under different cavity conditions

In highway tunnels, the presence of a cavity behind the lining can affect the contact between the lining and surrounding rock, leading to the concentration of pressure from the surrounding rock and acceleration of cracking in the tunnel structure. Thus, such cavities pose significant safety hazards. However, due to the complexity of the interaction between the cavity behind the lining and the surrounding rock, it is challenging to clarify the mechanism of damage caused by the cavity. In this study, we developed a mechanical model for testing the linings of highway tunnels and conducted numerical simulations of the bearing capacity of the lining in the presence of cavities. The results showed that the presence of a cavity behind the arch crown significantly affected the overall lining structure along with the stress state and deformation of the lining, leading to cracking at the arch crown of the lining. In contrast, the effects of single voids at the arch shoulder and arch waist were relatively small. When the cavity is located on one side of the lining, the effect of the deviation angle of the cavity center on the overall safety factor of the lining becomes more significant, with a maximum decrease of 62% in the safety factor. This study provides an essential reference for detecting and evaluating tunnels during operation when voids are present behind the lining.