| Shield tunneling is a common method of underground tunnel excavation.Shield tunneling through buildings,soil disturbance will cause ground settlement and building deformation,which will even affect normal use if it exceeds a certain limit.Therefore,this paper summarizes the influence mechanism and law of shield tunneling,based on a double shield tunnel 600 inclined put on six layers of frame structure building as the engineering background,through the finite element software MIDAS/GTS,analysis of shield tunnel construction on the surface and the ground subsidence and deformation characteristics of buildings,and the results are compared with the measured data.On this basis,the changes of excavation sequence and position relation are compared and the corresponding control measures are proposed.The research results show that:(1)Double-line shield tunnelingl is tunneled diagonally through the entire building at the same time,the settlement conforms to the space-time effect.Under the additional stress of the superstructure,the settlement increased by 3mm and the settlement groove was no longer symmetrical and smooth.The scope and mutation change with the location of the building.The maximum construction influence range is within 30m around the center of the two tunnels,and the disturbance settlement occurs within 15m before the shield construction reaches the building.(2)When the double-line tunnel is fully excavated,The maximum vertical settlement is-9.75mm in the middle of the building,lateral+2.93mm deviation occurred in the front left of the building,while lateral-2.27mm deviation occurred in the rear right,which is not much different from the measured data.The horizontal offset increases gradually from bottom to top,and the whole building has a downward trend.The frame column is bent.The axial force and bending moment of the left and right side columns of the frame building change more significantly than that of the middle column,which tends to decrease gradually from the bottom up.The change of axial force is more obvious than that of bending moment.(3)According to the construction order of digging the right line first and then the left line,the settlement slot is shifted from directly above the right line tunnel to above the central axis of the two tunnels.After the right line excavation,the settlement of the right side of the building is up to a maximum of-6.39mm,after the excavation of both tunnels,the maximum settlement moved to the middle of the building,with a value of-9.78mm.The settlement and axial force changes of the monitoring points were superimposed twice due to the influence of the two tunnel excavations,but there was no significant difference between the final value and that of the simultaneous tunneling.(4)Double shield tunneling when only the right line runs diagonally through the left side of the building at the same time,local subsidence occurs on the traversed side,the maximum settlement of-12.10mm occurred in the left rear of the building,and the maximum uplift of+2.17mm occurred in the right front of the building.The building as a whole has a trend of leaning to the left.The maximum horizontal offset value is the top layer-7.92mm,and the maximum tilt rate is 0.308‰.It is more than three times higher than the maximum tilt rate during the previous two construction periods.It indicates that the inclined side is more likely to cause the uneven settlement of the structure and cause the inclined failure.(5)In order to avoid serious surface deformation and structural damage under the above construction conditions,numerical simulation combined with shield machine construction control and building reinforcement control measures to cooperate with construction site monitoring to ensure construction quality and safety. |
