Effect Of Blasting Excavation On The Structure Safety Of Existing Tunnel Adjacent To The New Tunnel

By means of transform the existing railway to double line railway, we can improve the transportation efficiency and transport capacity not to mention saving investment. In the construction process of double line tunnel, it is a very common phenomenon that the clear distance between the existing tunnel and the new tunnel was small and lead to this problem: the blasting earthquake wave induced by blasting excavation endangers the safety of concrete lining of existing tunnel and the effect of blasting exerted on the operations of existing tunnel was adverse.In this paper, based on the practical situation of double line tunnel in No.2 Yu-Huai railway, the dynamic characteristics of the existing tunnel resulted from blasting excavation was studied by means of numerical simulation. The main work is:①Elaborate the theories of rock blasting fragmentation mechanism , especially the development and application in the tunnel project of the theory of control blasting. Elaborate the types and features of blasting earthquake wave. By analyzing evaluation standard of rock blasting both at home and abroad, summarizing a new safety criteria about peak particle velocity (ppv).②Tunnel blasting is simulated through ANSYS/LS-DYNA dynamical finite element program to get seismic wave's transmission law. Some examples about vibration influence of tunneling blasting on the existing tunnel were analyzed, such as different types of surrounding rock. By comparing the distribution and the time-course curves of ppv and stress, some conclusions are obtained.③From the maximum ppv perspective, combine with the Safety regulations for blasting, provide the construction program which would ensure the safety of the existing tunnel.④From the stress distribution and the time-course curves perspective, analyzing the rationality and defect of the Safety regulations for blasting.⑤Provide the double blast information construction program which would solve the contradiction about construction progress and safety of the existing tunnel.