The Adjacent Influenced Partition And Deformation Control Technology Of Overlapping Tunnel With Small Radius Curve

This paper has a systematic study on the key construction technology of overlapping tunnel with small radius curve through engineering analogy, numerical calculation and on-site measure, and so on, which takes the Nanluoguxiang Station-East station overlapping tunnel section project of Beijing Metro Line6as background, aiming at adjacent excavation problem of urban uderground, around the adjacent influenced partition, strata deformation control and optimization of construction scheme and other key technologies.The following achievement and outcome was gained:(1) Combined with the basic theory of adjacent influenced partition, the paper puts forward the standard of adjacent construction influenced partition for overlapped tunnel based on the additional deformation. And then with numerical calculation method, the paper analyzes mutual influence degree of excavation-shield overlapping tunnel and two-hole overlapping shield tunnel, from surface additional deformation, tunnel side additional deformation and plastic zone layout, divides adjacent partition into3areas(intensive-effect area, weak-effect area, no-effect area).(2) Contrast to the mutual influence degree of excavation-shield overlapping tunnel and two-hole overlapping shield tunnel, this paper concluded that the shield excavation can better control the mutual influence and the construction risk of overlapping tunnel. And then, the paper puts forward proper construction-safety controlling countermeasures, aiming at the adjacent construction characteristics.(3) Through numerical calculation method, this paper has a study on the surrounding strata deformation law caused by shield at small radius curve condition. The construction of shield tunnel with small radius curve leads to the asymmetric distribution of the strata deformation and plastic zone, the smaller the curve radius, the more obvious the asymmetry of strata deformation and plastic zone. Use the equivalent circle zone simulate the overbreak of the shield, shield tail interspace, grouting, and so on, the thicker the equivalent circle zone, the greater the stratum deformation. About the impact of asymmetric thrust, the greater the difference of left and right, the more obvious the asymmetry of strata deformation, the greater the total jack thrust, the smaller the surface settlement. And then, the paper puts forward proper construction-safety controlling countermeasures, aiming at the tunnel construction with small radius curve. (4) The research result of the overlapping tunnel adjacent partition has been fully applied in Nanluoguxiang Station-East station overlapping tunnel section project of Beijing Metro Line6. The research result of the overlapping tunnel adjacent partition and the surrounding strata deformation law caused by shield at small radius curve condition was considered to be scientific and rational according to the project and field testing result. Contrast to the monitoring results of the excavation-shield overlapping tunnel project and two-hole overlapping shield tunnel project, this paper concluded that the shield excavation can better control the surface settlement, Reduce the construction disturbance and risk.