Coupling Analysis Model Of Surrounding Rock-pressure Slurry-segment Of Large-section Curve Shield Engineering And Its Application

Curviline shield is widely used in urban tunnel construction,but its influence on the surrounding environment is more complex.At present,the researches on surface settlement caused by shield tunneling mainly focus on straight tunnel and horizontal curve tunnel,while the researches on surface settlement caused by grouting pressure and tunneling direction under vertical curve shield tunneling are relatively few.Based on the reconstruction project of East Sixth Ring Road(Beijing-Harbin Expressway ～ Luyuan North Street)in Tongzhou District,Beijing,this paper uses field measurement methods,theoretical analysis methods and numerical simulation methods to study the surface soil deformation law caused by largesection vertical curve shield.The main research contents and achievements are as follows:(1)Considering the turning direction and Angle of vertical tunneling,the surface settlement calculation formula caused by additional thrust of excavation face,friction resistance of shield shell,grouting pressure of shield tail and formation loss is derived based on Mindlin,and the feasibility of the formula is analyzed and verified with engineering examples.The results show that the soil uplift before excavation is mainly related to the friction resistance of shield shell,and the soil uplift after excavation is mainly caused by the grouting pressure of shield tail.The surface subsidence is mainly affected by the formation loss.The surface deformation caused by the additional thrust of the excavation face and the friction resistance of the shield presents an antisymmetric distribution.The uplift value of the shield tail grouting pressure reaches its maximum at the place where the segment is removed from the shield tail,and gradually decreases to the surface uplift value on both sides along this position,showing a symmetrical distribution.The difference coefficient of thrust and friction resistance is positively correlated with the surface settlement value,while the radius of the curve is negatively correlated with the surface settlement value.(2)The finite element analysis software ABAQUS was used to simulate the grout action by applying grouting pressure on the outer wall of the segment and the inner wall of the tunnel and establishing grout softening layer around the segment.The coupling analysis model of the segment,grout and surrounding rock was established,and the comparative analysis was carried out based on the measured engineering data.The variation trend of surface settlement is basically the same between the simulated value and the measured value,and the comparison results verify the rationality of the model.The numerical simulation results show that the surface settlement in the first stage and the second stage accounts for the largest proportion of the total settlement,which is related to the stability of the excavation face.The fifth stage accounts for the smallest proportion,which is related to the selection of parameters of grout softening layer and the setting of grouting pressure.(3)Based on the coupling analysis model of vertical curve shield segment,slurry and surrounding rock,the influence of different factors on the surface settlement was explored.The results show that the surface settlement value increases with the decrease of the curve radius.With the increase of tunnel depth,the surface settlement decreases gradually and the width of the surface settlement trough increases gradually.With the increase of the support force of the face,the surface settlement and the width of the transverse settlement trough decrease gradually.With the increase of grouting pressure,the surface settlement value decreases gradually.