Analysis On Seismic Response Of Damaged Lining Structure

Covering close to 9.6 million square kilometers, China is the world’s third-largest country by total area. The topographic and geological condition is pretty complex especially in the west part of China. In response to the national strategy of developing west regions, building traffic line to west part of China has been a top priority. Except for highway transportation and air transportation, rail transportation has been the main type of transportation connecting west part of China and east part of China because of its own advantages-fast and low freight. As an important part of the traffic line, many mountainous tunnels have been constructed and put into operation. However, the complicated topographic and geological conditions make many mountainous tunnels be easily harassed by many types of tunnel diseases. In fact, many mountainous tunnels are in operation with different tunnel diseases. Also, note that west part of China is in high seismic zone.This thesis mainly focuses on the seismic response of damaged lining structures. This thesis finishes the works as shown below.(1) Determination of the dimension of the tunnel model. FLAC3D is applied to establish tunnel models with transverse dimension (X direction) of 6 times,7 times, 8 times,9 times and 10 times the diameter of the cross section of tunnel. Then seismic load is applied to the bottom of the tunnel model in the transverse direction (X direction). Next, analysis on the seismic response is performed. The results indicate that when the transverse dimension (X direction) is no smaller than 8 times the diameter of the cross section of the tunnel, the effect of transverse dimension (X direction) on the seismic response tends to be stable. As a result, this thesis suggests that the transverse dimension (X direction) should adopt no smaller than 8 times the diameter of the cross section of the tunnel in order to eliminate the effect of transverse dimension on the seismic response.(2) Determination of the location and the range of the damaged parts. On the basis of the principle of dynamic strength reduction method, FLAC3D is adopted in this thesis to determine the location and the range of the damaged parts and the corresponding mechanical mechanism as well as the stability of the tunnel model. The results indicate that when the damaged part is at the crown, sidewall and the center of the invert respectively, the factors of safety of these three tunnel models are all equal to 0.85. When the damaged part extends on the crown, the factor of safety tends to be gradually small.(3) The First Point. On the basis of the principle of dynamic strength reduction method, FLAC3D is applied to analyze the safety and stability of the tunnel model with different types of cross section. The results indicate that the factor of safety of the circular tunnel is the highest among the analyzed tunnels (circular tunnel, three-centered circle tunnel and straight wall top arch tunnel); the factor of safety of straight wall top arch tunnel is the lowest; the factor of safety of three-centered circle tunnel ranges between that of circular tunnel and that of straight wall top arch tunnel. The Second Point. On the basis of the principle of dynamic strength reduction method, FLAC3D is applied to analyze the safety and stability of the tunnel models buried into different types of surrounding rock. The results indicate that the better the mechanical property of the surrounding rock is, the higher the factor of safety of the damaged tunnel become. The Third Point. On the basis of the principle of dynamic strength reduction method, FLAC3D is applied to analyze the safety and stability of the tunnel models with different buried depths. The results indicate that when the buried depth ranges from 2 times to 5 times the diameter of the cross section of the tunnel, it literally follows the law that with the increase of the buried depth, the safety of the tunnel model is enhanced. However, when the buried depth reaches at 8 times the diameter of the cross section of the tunnel, the factor of safety is smaller than that with buried depth being both 2 times and 5 times the diameter of the cross section. The Fourth Point. On the basis of the principle of dynamic strength reduction method, FLAC3D is applied to analyze the safety and stability of the tunnel model with the action of different durations of earthquake wave. The results indicate that the factor of safety of the tunnel model decreases with the increase of damage degree under the same duration of the earthquake wave; the longer the duration of the earthquake wave lasts, the more severe damages the lining structure suffers from.