Risk Assessment Of Safety Impact Of Shield Tunnel Construction On Adjacent Buildings

The development and utilization of urban underground space is one of the important development directions to solve the current shortage of land resources in the development of urbanization in China,and the subway,as an important way to alleviate urban traffic,is being built in more and more cities.Rapid urban tunnel engineering planning and construction also caused a series of problems,among which the damage caused by the tunnel construction of adjacent buildings is particularly prominent.How to determine the impact of tunnel excavation on the safety of buildings along the line before tunnel construction,and how to evaluate the potential damage of adjacent buildings caused by tunnel constru ction are of great practical significance for metro construction planning,line selecti on and risk avoidance,as well as to take appropriate risk control me asures.Tunnel excavation will cause the surrounding strata movement,which will cause the deformation and damage of adjacent building foundation and upper structure.Therefore,how to reasonably predict the strata movement caused by tunnel excavation is very important.Firstly,by analyzing the settlement law of the surface and the deep soil below the surface,the relationship between them is established.Then,based on the peck formula,by introducing the parameter a of different kinds of soil,the surface displacement release rateηof the tunnel face and the maximum slope k of the surface longitudinal settlement,the calculation model of the ground settlement induced by the construction of single and double tunnel shield tunnel is proposed,and several engineering examples are us ed The model is validated and analyzed.Then,considering the settlement and inclination of the building caused by the lateral settlement of the deep soil,and assuming that the building is completely flexible（i.e.subject to the surface deformation）,com bined with the risk level of the building damage,the risk range of the impact of the tunnel construction on the adjacent buildings is obtained,the calculation model of the risk range of the tunnel construction on the adjacent buildings is proposed,and t he tunnel diameter D and the foundation buried depth D are analyzed as well as the influence rule of formation loss rate V_L and other parameters on the size of building risk area,the range of risk area and its boundary values（C/D）₀ and（x/D）₀（C is the thickness of the soil layer on the tunnel,x is the horizontal distance between the building and the tunnel center）are derived and verified by numerical software.The model can be applied to the preliminary assessment of damage risk of adjacent buildings i n shield tunnel construction.Then,in order to evaluate the damage risk of adjacent buildings in shield tunnel construction in detail,based on the statistical analysis of the damage mode and damage accident of the building structure,two kinds of commo n building structures,brick concrete structure and frame structure,are sel ected as the research objects,and through the establishment of different kinds of building deformation control indexes,the harm of tunnel construction to buildings and buildings are also analyzed Finally,the risk assessment matrix is used to give the sa fety risk level of tunnel excavation to adjacent buildings.Finally,the detailed evaluation model is verified and analyzed with two engineering examples.The results show that the model proposed in this paper is reasonable and applicable.