Study On The Influence Of Cavities On The Tunnel Lining Under The Blasting Vibration

Currently, the researches on cavity are mainly carried out under static loading in domestic and international, but little study on the rule of dynamic response of tunnel lining, when there is a cavity behind the lining, has been undertaken as yet. Therefore, the research on the lining dynamic response of the tunnel lining with defects(e. g. cavity) under the seismic effect of blasting, and study the influence on the safety of the tunnel lining with a cavity under the blasting vibration, has important theoretical significance.The main contents and results are as follows:(1)Using the structural mechanics method, to dissect the failure mechanism of the tunnel lining with a cavity behind the vault. Research shows that the dome section most likely failure occurs; the worse the condition of surrounding rock, the larger the size of cavity, the larger the geometry parameters of the tunnel section, the more significant the pulling force on the outside of the dome lining will suffer.(2)Simplified the question of deep tunnel with a cavity behind dome into two adjacent circular holes in the full space which is made of isotropic elastic material. And according to previous theories, put forward a solution to the problem with plane incident SH waves.(3)With the help of MIDAS/GTS, to construct numerical models, and to carry out numerical simulation of the dynamic response of the existing tunnel with a cavity under the excavation blasting vibration in a contiguous new tunnel. The results showed that, the increase of the size in hoop direction and radial direction, has a reduced role to the horizontal velocity of the vault lining, while increases the velocity in vertical direction, and the former is more significant; under the action of blasting vibration, the most heavily impacted by the cavity is the arch footing toward the bursting side and the bottom.(4)Under the effect of blasting vibration, the protective measures of the tunnel lining with cavities behind it can be divided into two categories, named active protection measures and passive protection measures. And describes the specific measures and action principle separately. After that, using numerical simulation method to verify the protective effect of protective measures.