Study On Developmental Rule Of Regional Structure And Earthquake Mechanism In Tonghai Tunnel

Tonghai tunnel, with a total length of 10.302km, is the longest on Kunming-Hekou of yunnan international railway now under construction. The tunnel goes through that the region of crossover faults with SN and NW direction, which is Tonghai earthquake focus in 1970, which would suffer significant damage with earthquake disaster in the future.In the past, people thought that tunnel was restricted by the surrounding rock and soil, when earthquake came, tunnel would move alone with rock and soil, which is slight damage. Therefore, the research of active fault and earthquake resistant design of tunnel is rare. Alone with increasing the event of earthquake disaster in tunnel, many people have considered that is urgent.On basis of the construction of Tonghai tunnel, as well as on the collecting data of seismo-geology and seismic record, the developmental rule of regional structure and earthquake mechanism in tonghai tunnel, are studied by means of regional geological investigation and survey, deep-hole drilling exploration, Controlled Source Audio-frequency Magnetotellurics et al. in tonghai tunnel. Research on the distribution rule of deep regional active faults, the geophysical features, the features of new structure and regional strong earthquake, the developmental features of regional active structures in tonghai region. Research on the features of main active faults , characteristic of earthquake, spatial-temporal distribution of regional seismicity, as well as analysis tectonic earthquake hazard, distribution of regional earthquake focus, earthquake hazard and earthquake acceleration in the near field of Tonghai tunnel.In the near field of Tonghai tunnel, the research results show the movement features of crust new structure, which are whole uplift, difference rise and fall of faults block, faults strike-slip, cave and uplift of faults block, earthquake et al.The main faults strike are NW and NE and NNE direction. The active faults are strike-slip faults in Holocene and late-Pleistocene.The field is influenced by historical earthquake seriously, which is unsymmetrical in the spatial-temporal distribution of earthquake. The difference of seismicity is obvious in the earthquake intensity and frequency, which is less serious in the part south than that of the part north of the railway. The maximal earthquake intensity is X degree on the site of the railway in history. The earthquake intensity is strong and the earthquake frequency is high. The features of clustering occurring is remarkable,but the spatial-temporal distribution of earthquake is unsymmetrical in the field. The features of the clustering and continuously occurring are obvious with modern moderate-slight earthquake. In the next one hundred years, the level of seismicity will be the same as in 1900s'. Research illustrates that the spatial distribution and geological features for Zhougou fault (F_4-1), Guanying fault (F₄), Tonghai fault (F_11-2), Nizhe fault (F_11-3) and Wulongtang fault (F_11-4). The problem was solved in Tonghai tunnel by mean of Tunnel lining of anti-earthquake for active fault, to enlarge construction clearance of tunnel, to set deformation joint in boundary and inside of active fault zone. Thus, breakthrough has been achieved in the construction technology for tunnels under severe seismic zone, which has important guiding significance for future tunnels under similar geological conditions.