强风化花岗混合岩上硬下软地层公路隧道施工优化  

Optimization on Highway Tunnel Construction in Upper-hard Lower-weak Stratum with Intensely Weathered Granitic Migmatite

作　　者：袁刚 徐金峰 李守仁 石州 严绍明 YUAN Gang;XU Jin-feng;LI Shou-ren;SHI Zhou;YAN Shao-ming(Yunnan Communications Investment and Construction Group Co.,Ltd.,Kunming,Yunnan 650228,China;College of Civil Engineering,Tongji University,Shanghai 200092,China;Yunnan Lincang-Yunxian Expressway Co.,Ltd.,Lincang,Yunnan 675800,China)

机构地区：[1]云南省交投集团投资有限公司,云南昆明650228 [2]同济大学土木工程学院,上海200092 [3]云南临云高速公路有限公司,云南临沧675800

出　　处：《公路交通科技》2024年第7期153-162,共10页Journal of Highway and Transportation Research and Development

基　　金：云南省交通运输厅科技项目(云交科教便[2021]7号)。

摘　　要：针对临云高速公路特长隧道全、强风化花岗混合岩上硬下软地层的特殊地质情况,采用原开挖支护方案施工过程中围岩变形收敛较大并可能发生局部坍塌、冒顶等问题,结合隧道变形监测结果,针对性提出缩短隧道台阶长度+锚杆长度及布置的优化方案,并通过有限差分数值模拟软件对不同开挖支护工况的围岩压力、隧道变形、锚杆轴力和塑性区深度等进行对比分析。结果表明:隧道采用台阶法施工时,开挖至硬、软岩层交界处附近,由于拱脚下围岩性质软弱,无法形成可靠的支撑,上覆岩土体会挤压衬砌使其产生较大的沉降和收敛变形,且该交界位置的围岩压力最小;上硬下软地层隧道开挖过程中,中台阶开挖支护对隧道变形收敛影响最大,随着中台阶长度的缩短,隧道变形收敛逐渐减小,围岩压力逐渐增大;短锚杆对围岩的变形控制作用较弱,增长锚杆长度可以更好发挥锚杆的悬吊增强作用,充分利用了围岩的承载能力,减小了开挖支护后隧道的变形;采用上台阶、中台阶、下台阶、仰拱长度分别为4,6,2,2 m,锚杆长度分别为4.5,6.0,6.0,4.5 m的开挖支护方案既可以满足隧道变形收敛要求,也可以方便实际施工,保证了隧道的安全、快速掘进。Aiming at the special geological conditions of Lincang-Yunxian expressway tunnel,where the geological layers consist of fully and intensely weathered granite mixed rock with upper-hard lower-weak stratum,the original excavation and support scheme would lead to significant deformation and convergence issues in the surrounding rock during construction process.This could potentially result in local collapses,roof caving,and other problems.Therefore,in the conjunction with tunnel deformation monitoring result,the targeted proposal was made to optimize the tunnel step length,anchor rod length,and arrangement.The comparative analysis was conducted through finite difference numerical simulation software to assess surrounding rock pressure,tunnel deformation,anchor rod axial force,and depth of plastic zone under different excavation and support conditions.The result indicates that when the tunnel is constructed by using step method and excavated near the boundary between hard and soft rock stratum,the weak nature of surrounding rock under arch foot prevents the formation of reliable support,leading to significant settlement and convergence deformation of overlying soil,with the minimum surrounding rock pressure occurring at boundary position.In the excavation process of tunnels in upper-hard lower-weak stratum,the excavation and support during middle step excavation have the greatest influence on tunnel deformation convergence.As the length of middle step shortens,tunnel deformation convergence gradually decreases,while surrounding rock pressure increases.The short anchor rods have weaker control influence on the deformation of surrounding rock.Increasing the length of anchor rod can better enhance its suspension effect,fully utilizing the bearing capacity of surrounding rock,and reducing the deformation of tunnel after excavation and support.The excavation and support scheme with step lengths of 4,6,2,2 m for upper,middle,lower steps,and anchor rod lengths of 4.5,6.0,6.0,4.5 m respectively,which meet the requirements fo

关 键 词：隧道工程 施工优化 数值模拟 台阶长度 锚杆布置 上硬下软地层 

分 类 号：U455.7[建筑科学—桥梁与隧道工程]