软土地层三线小角度叠交盾构隧道施工影响规律及位移控制

Construction Impact Laws and Displacement Control of Three⁃Line Small Angle Overlapping Shield Tunnels in Soft Soil Layer

天津地铁6号线入出段线盾构隧道上穿既有隧道,通过现场实测和数值模拟对既有隧道结构变形规律、变形影响因素、不同变形控制措施的效果进行了研究。结果表明:盾构上穿过程中既有隧道竖向位移整体呈现出隆起-沉降-隆起的变化规律;刀盘距叠交部位断面距离L=2.0D(D为隧道直径)时,叠交部位断面轴力达到最大值,L=0~2.0D时,叠交部位断面弯矩逐渐由L≤0时的横8字形转变为L≥2.0D时的三叶草形;新建隧道与既有隧道的叠交角度在15°~60°、竖向净距小于1.0D时,既有隧道竖向位移受新建隧道影响较大,实际工程中应使叠交角度大于60°,竖向净距大于1.0D;设置支撑台车后,支撑台车影响范围约为2倍台车长度,在影响范围内横断面位移得到控制,但随着支撑台车离开,原来位置处对位移的控制效果逐渐消失;与不注浆相比,深孔注浆加固后既有隧道竖向位移最大值和水平位移最大值分别减小了67.4%、76.0%。

The shield tunnel of the entry and exit section of Tianjin Metro Line No.6 up-crosses the existing tunnel.Through on-site measurement and numerical simulation,the deformation law of the existing tunnel structure,deformation influencing factors,and the effect of different deformation control measures were studied.The results show that during the process of shield tunnel up-crossing,the vertical displacement of the existing tunnel shows an overall pattern of uplift-settlement-uplift.When the distance between the cutterhead and the overlapping section is L=2.0D(D is the tunnel diameter),the axial force of the overlapping section reaches its maximum value.When L=0~2.0D,the bending moment of the overlapping section gradually changes from a transverse eight shape with L≤0 to a clover shape with L≥2.0D.When the overlap angle between a new tunnel and an existing tunnel is between 15°~60°and the vertical clearance is less than 1.0D,the vertical displacement of the existing tunnel is greatly affected by the new tunnel.In actual engineering,the overlap angle should be greater than 60°and the vertical clearance should be greater than 1.0D.After setting up the support trolley,the influence range of the support trolley is about twice the length of the trolley,and the cross-sectional displacement is controlled within the influence range.However,as the support trolley leaves,the control effect on displacement at its original position gradually disappears.Compared with no grouting,the maximum vertical displacement and maximum horizontal displacement of the existing tunnel after deep hole grouting reinforcement is decreased by 67.4%and 76.0%,respectively.