Research On The Influence Of Shield Machine Postures To Segment Force During Combination Construction

In the present stage of construction subway tunnel in city,the application of shield method is more common.Combination construction with its fast construction,short construction period,high economic efficiency,and can overcome the problems encountered by the shield method,has been more and more widely used.Contrapose the combination of construction,to have analyzed the impact of stress on the segment when the shield posture changed.Shield posture is a state to ensure that the shield is designed according to the axis of advance,by the automatic measurement system or artificial measurement system,the measured shield machine axis from the design line.It’s great influence of shield attitude on the stress of the segment,in the construction stage,effect is more obvious.Combine section tunnel of Wangjiawan Station-Zongguan station in Line 3,Wuhan Metro,using the finite element analysis,the establishment of the20 loops of stress model of segment.When the simulation,the segment is as homogeneous ring,neglecting the effect of segment joints,the constitutive model is plastic model of Mohr-Kulun.Analyze the influence of the shield posture to stress on segment in combination construction.The main contents are as follows:(1)Analyze segment mechanics in the process of empty pushIn the combination construction,segment is influenced by Jack thrust,friction and extrusion of lining rings,and grip of pressure of backfilling of pea gravel and grouting Outside the rings.Under combination of these force,analysis the longitudinal,transverse stress and displacement of segments.(2)Analyze the Effect of the force on the segment when Shield Machine’s posture changesIn the combination of construction,shield posture often change.When the shield machine thrust size,thrust direction changes,shield posture also produces change,analysis of stress and displacement of the segment.(3)Research on attitude control method of shield machineCombination the stress of the segment and effect factors of shield segment,and put forward shield posture adjustment method,to improving segment stress conditions.In this paper,by using the combined method of numerical simulation and theoretical analysis,based on the combination of the construction of shield posture the impact on the segment force are analyzed.The following conclusions are drawn:Thrust increases,the displacement and longitudinal stress of the segment will increase;Change the thrust direction,when thrust completely provided by the shield construction machine,the displacement and longitudinal stress of the segment will first increases and then decreases;When the thrust increases,exceeding the maximum thrust of shield machine provided,need to exert force measures,the displacement and longitudinal stress tends to decrease.Research methods and conclusions have practical guiding significance on the similar projects to choose the appropriate thrust and the direction of advance,optimize the segment force,adjustment shield posture.