Study On The Safe Avoid Distance Of Metro Tunnel In Ground Fissures Site

The ground fissure is a special urban geological hazard in Xi’an, which brings a seriousthreat to Xi ’an subway construction. How to solve the problem of the subway tunnel goingthrough the ground fissure site is the key to Xi’an subway construction. Taking Xi ’an metroline No.3going through the ground fissure area as the research object, combined domesticand foreign research status of ground fissures, based on the features and trend prediction offuture activities of ground fissure, the safe avoid distance of subway tunnel going through thehangwall and footwall of ground fissure zone was studied.With the large-scale model test of subway tunnel parallelly going through the hangwallof ground fissure, the deformation characteristics, influence scope and failure modes ofsubway tunnel wrere disclosed and the safety avoid distance of subway tunnel located on thehangwall parallelling to the ground fissure zone is determined as30m. At the same time,using the finite element software MIDAS/GTS, the numerical model of metro tunnel locatingin the hangwall and footwall of ground fissure was respectively established, given thecompulsory settlement displacement to simulate the activity of ground fissure,the influence ofthe different distance from ground fissure on metro tunnel including the change of lateralhorizontal displacement of surrounding soil and structure, internal force and macroscopicdeformation, etc. were analysed, compared with model test results, the behaviors of the metrotunnel crossing the hangwall and footwall of ground fissure were disclosed.Combined the characteristics of displacement field, structural deformation,internal forcesand the requirements of code of avoid distance for ground fissure sites,the safe avoid distanceof the hangwall and footwall of ground fissure was respectively proposed,namly30m in thehangwall and15m in the footwall of ground fissure for metro tunnel crossing the groundfissure site.The results may provide a scientific basis for the theoretical guidance and designdesign, construction and safe operation of Xi’an Metro Line and followed other lines ofsimilar projects,and further enrich the research of ground fissure impact of underground structures.