为掌握昔格达组地层大断面隧道变形特征，确保大断面隧道施工期间围岩的稳定性，以改建铁路成都至昆明线米易至攀枝花段桐梓林隧道为依托，采用数值模拟与现场多断面监测相结合的方法，研究在三台阶临时仰拱法施工中昔格达组地层大断面隧道变形的时空效应。研究结果表明： 昔格达组地层大断面隧道洞周围岩变形以竖向沉降为主；拱顶先行沉降与上台阶开挖引起的拱顶沉降之和占总沉降的41.3%，超前影响范围为1.3D；隧道开挖期间拱顶沉降和拱脚水平收敛主要受中台阶开挖的影响；隧道拱顶沉降随时间变化的预测公式为U=102.105·exp(-5.33/X)；隧道拱脚水平收敛随时间变化的预测公式为L1=19.552·exp(-7.49/X)；隧道墙腰水平收敛随时间变化的预测公式为L2=17.862·exp(-23.26/X)。

The deformation characteristics of large crosssection Tongzilin Tunnel on MiyiPanzhihua Section on ChengduKunming Railway located in Xigeda Fm strata and constructed by three bench+temporary invert arch method are studied by numerical simulation and site monitoring, so as to guarantee the stability of surrounding rocks during construction. The study results show that: 1) The deformations of surrounding rocks of large crosssection tunnel in Xigeda Fm strata are mainly along vertical direction. 2) The primary crown top settlement and crown top settlement induced by top heading excavation takes 41.3% in total settlement; and the advanced influencing range is 1.3D. 3) The crown top settlement and arch feet convergence are mainly affected by middle bench excavation. 4) The prediction formula for crown top settlement vs. time is U=102.105·exp(-5.33/X). 5) The prediction formula for horizontal convergence of arch feet vs. time is L1=19.552·exp(-7.49/X). 6) The prediction formula for horizontal convergence of tunnel wall waist vs. time is L2=17.862·exp(-23.26/X).