Deployment process and size optimization of the inflatable plug for sealing a large section tunnel fire

• The finite element method can be well used to simulate the whole process of inflatable plug deployment in the large section tunnel. • The stress evolution during the deployment of the inflatable plug is analyzed, and the deformation stage of the material under normal working internal pressure was clarified. • The influence of inflatable plug size and installation position on sealing capacity was clarified, and the relationship between leakage area and inflatable volume was established, which affects the balance between sealing area and inflatable speed. Compared with traditional sandbag and roller shutter door, the inflatable plug is expected to be an economical, fast and effective tunnel sealing method. When the inflatable plug is used to seal the large section highway tunnel fire, the complex tunnel boundary affects the sealing capacity and stress evolution of the inflatable plug after deployment. It is also necessary to establish the relationship between the plug dimensions and the sealing effectiveness. This paper analyses the whole process of deflation, folding, installation and deployment of the inflatable plug in the large section tunnel through numerical simulation. The stress evolution of the inflatable plug was clarified. The sealing capacity of the inflatable plug was investigated using contact area and leakage area as indicators, and the relationship between the tunnel sealing ratio and the inflatable plug size was determined. The research results show that there is a stress concentration area in the inflatable plug after deployment, and the maximum stress decreases with the increase of the internal pressure in the inflatable plug. The sizes of the inflatable plug, especially the radius, have a significant effect on the sealing capacity. The leakage area of the inflatable plug showed an exponentially decreasing negative relationship with the inflation volume. Additionally, compared with installed in the tunnel top, installing the inflatable plug on the tunnel side can improve the sealing capacity, but will increase the probability of inflatable plug failure. This work can be references for the design of the inflatable plug to seal tunnel disasters.