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昔格达组地层是一种分布于我国西南地区的河湖相沉积半成岩,水稳性差,遇水易泥化、崩解,强度大幅度降低,在隧道开挖过程中易产生围岩大变形、初期支护结构开裂、掉块、坍塌冒顶等灾害事故,严重影响着交通隧道工程的建设。以改建铁路成都~昆明线米易~攀枝花段桐梓林隧道为工程背景,运用FLAC3D数值仿真软件,建立5种施工工法模型。从隧道围岩变形时空效应特征角度,对比分析昔格达组地层在不同施工工法中的变形响应。研究结果表明,不同施工工法对隧道拱顶沉降影响最大;当隧道设计预留变形量为10~15cm时,建议优先选择三台阶临时仰拱法;当隧道设计预留变形量为10cm以内时,建议优先选择CRD法;最先行开挖面最大挤出变形量与最先行开挖面面积近似呈线性正相关;采用预留核心或增加较大刚度的临时闭合支撑有利于控制掌子面挤出变形。
The Xigeda Formation is a kind of sedimentary semi-diagenesis of rivers and lakes distributed in the southwest of China. Its water stability is poor. When the water is easy to mud and disintegration, the strength of the Xigeda Formation is drastically reduced. It is easy to produce the large surrounding rock in the process of tunnel excavation Deformation, the initial support structure cracking, falling blocks, collapsed roof collapse and other disasters, seriously affecting the traffic tunnel construction. Based on the engineering background of the Tongzilin tunnel in Mianyi ~ Panzhihua section of Chengdu-Kunming-Kunming railway line, five construction methods were established by using FLAC3D numerical simulation software. From the perspective of the time-space effect of tunnel deformation, the deformation responses of the Xigeda Formation in different construction methods were compared. The results show that different construction methods have the greatest impact on the settlement of the tunnel vault. When the designed deformation of the tunnel is 10 ~ 15cm, it is suggested to choose the three-step temporary inverted arch method. When the designed deformation of the tunnel is less than 10cm, It is suggested that the CRD method should be prioritized. The maximum displacement of the first excavation surface is linearly and linearly related to the area of the first excavation surface. Temporary closure support with reserved core or increased stiffness is advantageous for control of extrusion Deformation.