Study On Settlement Control Of Zhengzhou Subway Shield Tunnels Undergoing Existing Building

It will cause formation disturbance and ground deformation using shield method construction.Tunnels are inevitably constructed under existing buildings,underground pipelines and bridges,etc.due to the environmental restrictions and traffic requirements.It's necessary to study the influence of shield tunneling on the environment nearby.This paper studies the risk control measures of shielding tunneling undergoing buildings and the main contents and results are as follows:(1)The mechanism and variation rule of ground settlement caused by shield driving are analyzed.The ground settlement mainly occurs in the three stages: shield cutting arrival,shield passage and shield tail prolapse,and the settlement accounts 86% of the total settlement.The failure index and current code of buildings are studied,and the deformation limits of buildings are analyzed.For buildings with larger stiffness,the overall inclination rate should be used as the main control index and for long strip buildings,cracks(or local differential settlement)should be used as the main control index.(2)The main reason for the large settlement of the strip-shaped foundation building in the early stage is that the pressure of soil silo does not increase synchronously with the excavation depth,and Synchronous grouting is not in time.After taking measures,the total settlement of the buildings duiring the newly excavating is obviously reduced to 24% of the original maximum settlement.Although the total settlement value of the building is larger than the control value set by the code and the scheme,the differential settlement is still within the allowable scope of the code,and there are no obvious cracks in the appearance.It is confirmed that the main damage index of shallow foundation building is differential settlement,and if cracks occur,the change of cracks should be observed.(3)In the study of risk management and control of subway shield tunneling through buildings,firstly,the establishment of risk management system is introduced as a whole,and the organizational structure and responsibilities of risk management system are defined.And then,taking a shield tunnel under construction in Zhengzhou as an example,this paper introduces the risk assessment during the construction preparation period of shield tunnel.Finally,the whole process risk management and control measures of Underpass buildings are studied.It avoids the loopholes in management and provides management support for shield tunneling underneath risk sources.