Analysis Of The Settlement Of Utility Tunnel Due To Shield Tunneling Of Metro Twin Tunnels Crossing The Existing Utility Tunnel From Its Bottom

When the double-tube parallel tunnels shield under-passing,the utility tunnel over the tunnels would produce displacement.For site construction,strict control of construction parameters is necessary to avoid excessive displacement of utility tunnel.Based on the engineering background of Guangzhou Metro Line 11,this thesis deals with the variation law of stratum displacement corresponding to utility tunnel displacement during shield tunneling by theoretical calculation,and the law is further verified by numerical simulation.Taking the stress of elliptical orifice as the research object,the mechanism of the settlement tank of the utility corridor which change with the angle of intersection is analyzed.According to the Peck formula of the data inverse fitting correction obtained by numerical simulation proves that the displacement of the pipe gallery accords with the theory of Gaussian regular distribution curve.Conclusions are obtained through research and analysis as follow:(1)For the stratum without pipeline or less rigidity of pipeline,the settlement curve formed by shield propulsion force on the surface longitudinally is symmetrical to the surface point corresponding to shield propelling surface.The settlement curve formed by the friction force between shield and surrounding soil on the surface longitudinally is symmetrical to the surface point corresponding to a certain distance behind the shield propelling surface,and the settlement curve of stratum displacement formed in the surface longitudinal is always the settlement value.(2)The soil displacement caused by shield tunneling increases continuously with the increase of formation depth,and decreases with the decrease of the offset of formation loss.(3)The results of theoretical calculation and numerical simulation show that with the decrease of the intersecting angle between the two parallel tunnels under shield tunneling the maximum value of the displacement settlement trough and the width of the settlement trough are gradually decreased and the width of the channel is gradually increased with the decrease of the intersecting angle between the two channels.(4)According to the numerical simulation results,the influence range of the settlement of the upper composite tunnel under shield tunneling is linearly related to the length of the intersection,and quadratic related to the area of the intersection.(5)When the intersection angle decreases gradually,the centrifugal rate of the elliptical orifice corresponding to the cross section of the pipe gallery increases gradually,and the tension zone is gradually formed above and below the ellipse,and the pressure zone is larger on the left and right side,thus making the disturbance range of soil more extensive.(6)The modified Peck formula of two-hole parallel tunnels is fitted in reverse by the numerical simulation result,which verifies the theory that the displacement and settlement trough of pipe gallery accords with Gauss distribution curve.