Study On Numerical Simulation And Prevention And Control Of Ground Fissure In Xi’an F5 Based On FLAC3D

The collapsible loess distributes largely in Xi ’an.Xi ’an has been affected largely by the ground cracks and ground subsidence under the single or comprehensive action and influence of natural state or human activities.In this paper,a large-scale comprehensive planning project in Xi’an is taken as an example to study the spatial distribution,ground fissure characteristics and evolution characteristics of ground fissures,which is threatened by ground fissures.Combined with the actual situation of the construction project,a scientific and reasonable safe avoidance distance is proposed to ensure the long-term safety of the construction process and buildings and the safety of people’s lives and properties.On the basis of field investigation,referring to the corresponding engineering specifications and building levels,the safe avoidance distance between the upper and lower walls of the studied ground fissures is determined.The finite element numerical simulation model based on FLAC3D is established and the reasonable safe distance of the building is obtained when the ground fissure moves 5cm,20cm and 50cm horizontally at the upper and lower walls,which provides a solid geological basis for the planning project construction and a reliable guarantee for the safety and stability of the building.The main conclusions of this paper are as follows:the research project belongs to building class II(underground comprehensive pipe gallery),f5 ground fissures cross the proposed project between Changle Road and Hansen Road,so the influence of ground fissures on the building needs to be considered;the causes of ground fissures in Xi’an are mainly caused by a series of steep normal faults developed on the hanging wall of Lintong-Chang’an fracture,which is a single component of the structure,and accompanied by urban development.The spatial development of f5 ground fissures is uneven.Through the establishment of numerical simulation model of f5 ground fissures,when the fissures move vertically for 5cm,20cm and 50cm,the maximum avoidance distance of the upper wall is 30m,90m,223m,and the maximum avoidance distance of the lower wall is 25m,41m and 177m.According to the simulation results and the requirements of ground fracture code and the current situation of ground fracture activity,it is considered that the project should be safe and reasonable in the construction process according to 20m in the South(hanging wall)and 12m in the North(footwall)of f5 ground fissures.