Study On Seismic Response Rules Of Unsymmetrical Loading Tunnel Based On Large-scale Shaking Table Test

The terrain conditions in the western region of China are very complex and mainly mountainous and plateau.Tunnel, as an important form of traffic structure, is widely used in railway and mountain highway engineering. Due to the restriction of terrain, geological and environmental factors, it is inevitable that unsymmetrical loading tunnel is formed. In recent years, many earthquakes occurred in the western areas and the traffic facilities were damaged seriously in high intensity seismic region. Many highway tunnels, including a lot of unsymmetrical loading tunnels, were damaged in the 2008 Wenchuan earthquake. It was difficult to repair the damaged tunnels, which caused significant economic losses. Therefore, it is very necessary to study the seismic response rules of unsymmetrical loading tunnel, which has certain guiding significance for seismic design of unsymmetrical loading tunnel. Based on National Natural Science Foundation of China (number:51204125) " Seismic catastrophe behavior and anti-seismic performance evaluation of rock slope containing underground caverns", large scale shaking table test of unsymmetrical loading tunnel was completed and dynamic response characteristics of unsymmetrical loading tunnel were studied. MIDAS/NX finite element software was used to numerical simulation and the results were compared with the model test results. The key studies were as follows:(1) Unsymmetrical loading tunnel for large-scale shaking table testBased on similar theory, a large-scale shaking table model test of unsymmetrical loading tunnel with the scale of 1:10 was completed. The design principle of similarity relation was introduced and the main similarity coefficients of physical and mechanics were determined. The simulation materials and point layout schemes were also selected. Three seismic waves including Darui synthetic seiswave, Wenchuan earthquake wave and Kobe seismic wave were selected as input wave, and the excitation scheme were formulated.(2)Seismic response analysis of unsymmetrical loading tunnelAccording to shaking table model test data, the dynamic response of acceleration, dynamic strain and surrounding rock pressure under different seismic waves, its peak excitation acceleration and excitation directions were studied. The acceleration amplification factor was defined and the dynamic response of acceleration was analyzed from the horizontal aceleration amplification coefficient and the vertical acceleration amplification coefficient. The results showed that the difference of seismic response law of horizontal and vertical acceleration, and the seismic response was related to the type of seismic wave, the amplitude of the seismic wave and the location of the measuring points. In addition, one of the reasons why unsymmetrical loading tunnel was more easily damaged in earthquake was that the lining was applied to asymmetry force. The surrounding rock pressure generated by the horizontal seismic wave was greater than the vertical seismic wave, but surrounding rock pressure produced by XZ-excitation was not a simple superposition of horizontal and vertical.(3) Numerical simulation about dynamic response of unsymmetrical loading tunnelA three dimensional unsymmetrical loading tunnel was established by MIDAS/NX finite element software and Wenchuan wave (XZ) with different excitation intensity was given an example. The comparison analysis were conducted between numerical simulation results and model test of unsymmetrical loading tunnel. The results showed that the fitting degree of numerical simulation and model test was high, and numerical simulation results and shaking table model test results were all reasonable. Based on it, the distribution of inner force of unsymmetrical loading tunnel was analyzed by numerical simulation in earthquake.