Study On Seismic Response And Stabilization Of Tunnel With Shatter Rock Under Construction

Due to frequent earthquakes in recent years, more and more highway tunnels in our country were constructed inevitably in shattered rock. Shattered rock becomes more broken after repeated rubbing effect, it brought great security risk for safety construction. Many tunnels’surrounding rock in Guanggan are shattered rocks and a number of primary support and secondary lining cracks and even landslides occurred in the construction process under the aftershock, so its method needs to be improved because of lacking experience in its seismic stability analysis and safety control measures. This dissertation is based on the Guanggan highway tunnel research project. Firstly, the disasters that occurred in shattered rock are summarized and the influencing factors of tunnels’ seismic damage are studied. Then the dynamic response characteristics of the structure and surrounding rock under seismic action are studied. Lastly, this paper summarized the possible factors and mechanism of typical section’s instability under the dynamic action and studied the safety control measures during the construction. The main research contents and results are as follows:(1) By combining extensive literature and research data with the surrounding rock case revealed by the construction site, we make a count on surrounding rock in the earthquake area, generalized the shattered rock mass damage cases and their influencing factors.(2) Based on the engineering geological survey information and site conditions of Guanggan highway tunnels, the dynamic response characteristics of tunnel support structure in typical section during construction under the earthquake are analyzed by the method of numerical modeling. The presence of the supporting structure basically will not affect the dynamic response of the surrounding rock, and support with greater rigidity has bigger earthquake response, the parts which have largest dynamic response mainly exists in the spandrels and springing.(3) Cavity may exist behind the lining of Guanggan highway tunnels. By analysis of lining’s dynamic response characteristics, the results show that the presence of cavity does not affect the dynamic response law of other position of the structure, only leaves concentration phenomenon of the stress near the cavity, the structural forces generated within a certain range, and cavities will reduce the bearing capacity of the structure. Cavity and aftershocks is the main reason that led to the cracking of second lining according to the analysis.(4) According to the on-site monitoring and research data, combined with the results of dynamic response characteristics under different lining and cavity situation, the corresponding safety prevention and control measures are proposed.