| Along with modern industry development and urban scale expansion , traffic problems have become prominent day by day .By right of the advantage of the large carrying capacity ,safety and rapid ,subway has become the important measure which resolves the traffic problems of the city. However ,at the same time we enjoy the convenience and the fast which the subway provide us ,it also brings us negative effect which have aroused people's attentions .For one thing ,that is the problem which is induced by the construction of the subway . By lots of predominance , the shield tunneling is applied in the subway tunnel excavation more and more .However, the disturbance to the soil is unavoidable which may induce different levels of displacement and deformation of the stratum .And when the displacement and deformation of the ground are over a certain limit ,it will endanger the surrounding roads, nearby buildings and underground pipeline's security .In the next place ,it is the problem of the impact of vibration induced by the subway .While the development of the subway is in the ascendant , the noise and vibration problems caused by subway have gradually emerged . As the primary traffic route of the city ,subway tunnel often drill through the urban areas which is sensitive to the vibration and the yawp .When the train is running in the underground tunnel ,the upside buildings and people would be influenced by the yawp and the vibration of the foundation or the earth's surface which is caused by the subway.As the famous ancient capital which came through 13 dynasties, ancient buildings which are preserved so far in xi'an are widely distributed .One of the most important and outstanding problem induced by the subway project construction in xi'an is how to avoid or reduce the influence of the construction and the operation of the subway on the ancient buildings to the utmost extent .Bell tower is a landmark building in Xi'an, which is the important national heritage conservation units , and hold significant historical status and cultural connotation .The NO.2 and the NO.6 route of the xi'an subway surround the bell tower ,the subway construction may cause the stratum settlement and the running of the subway may induce the vibration ,all of which could endanger the safety of the bell tower.Not only to ensure the realization of planning route, but also to guarantee the safety of cultural relics ,it is a difficult problem .By means of the large-scale finite element analysis software-ANSYS, through the establishment of three-dimensional finite element model including bell tower ,tower base ,surrounding stratum and subway tunnel: 1) achieving the circulation of the subway tunnel excavation process by making use of the element killing technique and the Macro Document of ANSYS Parametric Design Language (APDL), simulating and calculating the displacement and deformation of the stratum induced by the shield tunneling excavation in both case of the single tunnel and double tunnel excavation, analyzing the influence of the shield tunneling excavation on the bell tower and the surrounding stratum at different engineering stage .2)achieving the simulation of the subway vibration loading by means of the Table Parameter of the APDL ,and then by making use of the transient dynamics analysis ,simulating and calculating the influence of the subway vibration on the bell tower in three case of different speed of the train ,further more, analyzing the influence of the vibration on the bell tower by combining the FEM results and the field survey of the effect of ground traffic loading, consequently ,gained some useful conclusions ,and in hope of what we present can provide reference for the study of the influence of the subway on the ancient architecture ,in order to promote coordinated development between urban construction and ancient architecture protection. |
