| Segment lining as one of the three major elements of shield construction has a pivotal position,the stress and deformation is importment for the safety and quality in the construction and operation of the sheild tunnel.The stress of segment lining in the construction process is complex,diverse,this paper base on the takes lanzhou subway shield tunnel between YingMentan station and Matan station.Segment stress analysis model is established on the basis of actual data,different angles of the jack were studied on the segment displacement,stress,bolt axial force and shear force,the influence of segment clearance,in the case of emphatical analysis about segment grouting pressure.Specific content is as follows:The dispersion characteristics of Bingham fluid were analyzed by considering the timevarying characteristics of slurry viscosity,the weight of grout,the effect of groundwater and grout diffusion boundary conditions,the grout diffusion distance calculation formula and the slurry to segment pressure dissipation formula were obtained.A numerical analysis model was established by analyzing the jack force of shield machine up or down or travelling around to analyze the stress and deformation of segment and bolts for a total of 33 kinds of working condition.The results showed that:(1)Jack of the shield has a greater influence on the vertical and horizontal displacement of segments in the shield tail steel ring,and with the degree increase of Angle of jack,the influence is bigger.(2)The angles of jack shield had a greater impact on the maximum principal stress of segments than the minimum principal stress,and growth rate of the maximum principal stress can reach the minimum principal stress growth rate of more than 10 times;when the shield machine downward can reduce the maximum principal stress of segment,maximum principal stress of segment can be reduced about 20% while angle of jack reaching to 2.0 °,and make segments stress more reasonable.(3)The maximum axial force of bolt appeared generally on loop ring to bolt with a recent piece of segment to the jack.For shield machine driving up or driving around,bolt axial force with the 2 degrees of jack can reach 8~9 times with the 0 degrees of jack.For shield machine driving down,bolt axial force increased with the decreased firstly,the minimuml value appeared on 0.8 degrees;The maximum shear of longitudinal bolts generally appeard between the 3th ring and 4th,the shear force was larger near the grouting hole and the bottom of segments.(4)The maximum shear stress of clearance generally appeard between the segment lining and surrounding rock,the maximum compressive stress was in the space between the segment ring,the bigger degrees of jack can made them increasing when shield machine driving up or around,and the bigger degrees of jack can made them reducing when shield machine driving down.The maximum shear stress of segment ring generally appeared between the 3th ring and 4th ring,its distribution in the segment size of axial force and the position of longitudinal bolts distribution,the distribution of shear stress had a relationship with the axial force of segments and the position of longitudinal bolts. |
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