Settlement Analysis Of Reinforced Area Of Assembled Shield Inspection And Repair Wells

In recent years,urban metro tunnel engineering in China has made considerable progress.Shield tunneling,with its advantages,has been more and more widely used in tunnel engineering,and has gradually become one of the main construction methods of Metro tunnel.However,there are some unavoidable problems in shield tunneling.In long-distance shield tunneling construction,the wear of cutter head is prominent,which results in slow advance speed and unstable pressure control,especially in sandy gravel strata in the north and southwest.In the actual construction process,there is a greater risk of direct warehouse opening for tool replacement.Therefore,tool head maintenance and tool replacement are often carried out by building maintenance wells in advance on the line.In recent years,due to the continuous development of the concept of recyclable and green construction,assembly steel structure is gradually emerging and applied in the field of shield cutter head overhaul wells.However,there are some problems in the practical application of the structure,the most important one is how to reduce the disturbance to the soil in the process of shield tunneling and cutter head maintenance to ensure the safety of the whole project.Based on the two practical applications of assembled overhaul wells on the Beijing New Airport Line,this paper discusses the reinforcement methods,reinforcement scope,procedures and preventive measures of the assembled structure,which are prone to settlement and deformation,in combination with field monitoring data.The main contents are as follows:(1)Based on the two-time repair project of assembled cutter head,the construction technology of this new structure is introduced,and the applicable conditions,advantages and disadvantages of deep hole grouting and high-pressure jet grouting are compared and analyzed.This paper studies the difference of actual effect in shield tunneling,shield tunneling and cutter head maintenance under two kinds of reinforcement methods,and gives suggestions on reinforcement technology selection under different engineering conditions.(2)The whole construction condition is modeled by numerical modeling software,and the settlement of the longitudinal length,transverse length and reinforcement strength of the reinforcement area is analyzed by changing the parameters of the reinforcement area.Finally,the reasonable reinforcement range of longitudinal,transverse and strength of the reinforcement area is given,and the suggestions for the reinforcement area under different reinforcement methods are given.(3)By analyzing the data of surface settlement,earth pressure and simulation results of two engineering examples,it is concluded that shield tunneling and cutter head rotating maintenance are the most important processes to cause soil deformation and settlement around the overhaul well,and the settlement occurs inside and around the overhaul well.The settlement value is closely related to the scope and strength of the reinforcement area.Finally,concrete measures to control settlement and construction risk are given: reasonable arrangement of reinforcement scope and reinforcement mode during the construction of overhaul wells;precise control of parameters such as earth silo pressure,cutter head thrust and propulsion position during shield tunneling;early warning of soil deformation and secondary reinforcement scheme during the overhaul of shield tunnels.