Analysis On The Dynamic Response Of A Twin Tunnel

With the rapid development of tunnel and underground structure construction, as a tunnel type, the twin tunnel has been applied in more and more fields. It is significant in economic and social development to study the stability of a twin tunnel under dynamic loads. In this paper, based on the the 1st Nanzhou Tunnel in the Jing-Fu highway, the response features of the tunnel under both blasting and earthquake dynamic loads is analyzed by FEM method , combining tunnel blasting monitor materials. This paper mainly includes several parts below:1. The method studying the effect on the stability of the twin tunnel under the blasting dynamic loads and earthquake is discussed. Aiming at the domestic and overseas studying status in quo, dynamic FEM calculation and analysis method, blasting vibration simulation, the set for the boundary condition, the choice of the element type, meshing, and the simulation and input of the seismic wave is precisely presented.2. After analyzing on the tunnel blasting monitor results, it is regarded that traffic tunnel blasting vibration control is potential according the blasting vibration control specification.3.Using the ANSYS software, the IV class entrance of the tunnel is simulated. The results presented that the most dangerous position of the lining and the surrounding rock is the sidewall close to the blasting under the effect of the excavated tunnel, of which the vibration velocity and the 1st principal stress is obvious greater than that of other position of the tunnel. Bias pressure affects the distribution of the vibration velocity and 1st principal stress of the lining of the twin tunnel, but it is not a major factor.4. Typical sections of the Class IV tunnel under different burial depth is chosen, to analyze the variation law between the vibration velocity of the key position and the burial depth. The relation curve is established, and the effect extent of the burial depth to the vibration velocity and the 1st principal stress is obtained.5. Using time and frequency method to simulate the earthquake dynamic response on the typical section of the Class IV and the entrance of the Class V tunnel. The relations between the stress characteristic of key position of the tunnel and the burial depth is analyzed. It is discovered that both Class V and IV tunnels resist the earthquake well. The foot of the wall is the major position which supports the force and the burial depth, on some level ,affects it.