Liquefaction-Induced Deformation And Anti-Seismic Measures For The Foundation Of Nanjing Subway

It is a frontier subject to study the effect of seismic liquefaction on subway structure. Integrating into the Science Foundation Project of liquefaction-induced deformation and anti-seismic measures for the foundation of Nanjing subway in the thesis, the multiple shear mechanism model is used for the foundation of Nanjing subway to simulate the behavior of the seismic liquefaction-induced deformation in sandy soil. In order to reducing the damage that seismic load gives rise to on the structure which is built on liquescent soil layers, the study of anti-seismic measures is conducted. The main work is introduced in the following:(1)The great finite element program of Flip, which is published in Japan, is utilized for subway foundation of Nanjing to analyze seismic liquefaction-induced deformation in sandy soil. Considered the result of the numerical calculation, the subway foundation of Nanjing will be kept stable if the earthquake of 7 degree breaks out.(2) In the thesis, some other important factors on the stability of subway foundation during earthquake are studied, for example, the intension of earthquake, the unit weight of the subway tunnel, the depth of the subway tunnel, the content of clay in sandy soil, and inputing different earthquake waves. The rudiment rules of the factors on the subway residual deformation are found and a empirical formula for the subway residual deformation is given, which can consider the unit weight of the subway tunael, the intension of earthquake. All of these sophisticate the theory of the design of subway tunnel.(3) In the thesis, the study of anti-seismic measures is conducted in the case of the earthquake of 8 degree. Through the numerical calculation for improved soil layers, there is an economical and reasonable improved zone whose depth is a constant but whose width is decided by the controlling residual deformation of subway structure. And a empirical formula for the subway residual deformation is given which can consider the improvement depth and width. At the same time, it is proved that residual liquescent soil layer has obvious effect of vibration absorb to improved cover layer.