摘要
针对后岭下隧道内引出联络线段设计跨度大、变截面横向扩挖尺寸长、安全风险高等特点,对三台阶临时仰拱法上台阶采用支立门架法和类正洞台阶法横向过渡扩挖的2种方案进行了数值模拟,即在10 m过渡段内上台阶分部开挖:纵向先、后行导坑开挖并架设竖向支撑,支点上部纵向加设连接梁或用槽钢将环向拱架纵连。然后拆除扩挖侧中间竖撑,形成横向扩挖门洞,扩挖施工中采取支立门架法防护或类正洞台阶法扩挖,并最终扩挖至拱脚,最后接长正洞环向拱架,完成过渡段上台阶施工。数值模拟分析结果表明,2种方法均安全可行,结合现场围岩实际情况,本工程采取了支立门架方案成功完成了扩挖,洞周土体变形的监测值和模拟值变化规律基本一致,土体位移与应力变化均小于模拟值,且在允许范围内。本案的成功实施为类似大跨度变截面隧道横向扩挖施工提供重要的参考和借鉴,具有重要的实用意义。
Aiming at the design characteristics of large span,long horizontal excavation size of variable section and high safety risk in the lead line section in Houlingxia Tunnel,the numerical simulation of two schemes of lateral transition excavation using the supporting gantry method and the quasi-cave step method for lateral transition excavation by three-step temporary inverted arch method was carried out,That is,the excavation of the upper step division within the 10 m transition section.The longitudinal first guide pit and the rear guide pit were excavated and vertical supports were erected,and the connecting beam was added longitudinally in the upper part of the fulcrum or the ring arch frame was connected longitudinally with channel steel.Then the middle vertical brace on the excavation side was removed to form a lateral excavation door hole.In the excavation construction,the support gantry method was used for protection or the quasi-cave step method for excavation.Finally,it was excavated to the arch foot,and the long main hole was connected to the arch frame to complete the construction of the upper steps of the transition section.The numerical simulation results show that both methods are safe and feasible.Combined with the actual situation of the surrounding rock on site,the project adopts the supporting gantry scheme to complete the excavation.The monitoring value of soil deformation around the cave is basically consistent with the variation law of the simulated value.The soil displacement and stress changes are less than the simulated values and within the allowable range.The successful implementation of this case might provide an important reference for the lateral excavation construction of similar large-span variable section tunnels,and has important practical significance.
作者
孙引浩
Sun Yinhao(No.1 Engineering Co.Ltd.of China Railway 20th Bureau Group,Suzhou 215151,China)
出处
《石家庄铁道大学学报（自然科学版）》
2023年第1期77-83,共7页
Journal of Shijiazhuang Tiedao University(Natural Science Edition)
基金
陕西省自然科学基础研究计划青年项目(2022JQ-563)。
关键词
大跨度隧道
变截面
横向扩挖
围岩稳定性分析
large-span tunnel
variable cross-section
transverse expansion excavation
stability analysis of surrounding rock
