摘要
大变形控制一直是高地应力软岩隧道设计与施工中面临的重要难题,其中变形控制基准更是适当变形释放、减少拆除的关键因素之一。为此,依托成兰铁路高地应力千枚岩隧道,通过大量工程实践,分析软岩隧道断面型式优化、锚杆支护技术、开挖方法优化、二衬施作时机等,提出成兰铁路软岩隧道大变形控制技术。进而通过大量变形量测数据统计,分析基于施工过程的隧道变形特征,考虑隧道测量丢失位移,确定隧道预留变形量,建立基于施工过程的隧道位移控制基准。研究结果表明:基于“主动控制”的软岩隧道支护理念,成兰铁路提出“优化断面,强化锚杆,减少开挖分步,动态调整,分级控制”的软岩隧道大变形控制技术,重点优化锚杆的类型、参数及施工机械等,使锚杆快锚固,早承载。针对不同大变形等级,逐渐优化隧道断面,尽量采用大断面开挖,既可以减少围岩扰动,又可以减少空间限制对长锚杆施作的影响,从而控制围岩变形,提高施工效率,二衬作为安全储备,在初支变形稳定后施作,保证结构的长期稳定性。高地应力千枚岩隧道变形具有显著的时空效应,随着大变形等级提高,仰拱施工后变形占比增大,变形时间效应增强;虽然不同大变形等级下隧道变形量具有一定的离散性,但统计样本显著地服从正态分布;考虑测量丢失变形,以正态分布样本平均值的95%的区间估计作为隧道预留变形量限值,建议成兰铁路轻微大变形段、中等大变形段、严重大变形段和极严重大变形段单线隧道预留变形量分别为10~20、25~35、35~45、大于45 cm,双线隧道预留变形量分别为20~30、25~40、40~60、大于60 cm。考虑大变形分级和开挖方法,基于隧道施工过程建立高地应力千枚岩隧道变形控制基准,通过监控量测实时监测隧道变形,及时采用措施,可以有效防止初支侵限。
Large deformation control has always been an important problem in the design and construction of high geo-stress soft rock tunnel,where the deformation control criteria are one of the key factors for proper deformation release and demolition reduction.Therefore,based on the high geo-stress phyllite tunnels of Chengdu—Lanzhou railway,and a large number of engineering practice,this paper analyzed the section type optimization,bolt support technology,excavation method optimization and timing of secondary lining of soft rock tunnel,and put forward the large deformation control technology for soft rock tunnels of Chengdu—Lanzhou railway.Then,based on a large number of deformation measurement data and statistics,the tunnel deformation characteristics based on the construction process were analyzed while the lost displacement of tunnel measurement was considered.The reserved deformation of the tunnel was determined before the establishment of the tunnel displacement control standard based on the construction process.The results show that based on the soft rock tunnel support concept of“active control”,a large deformation control technology of"optimizing cross-section,strengthening anchor bolt,reducing excavation step by step,dynamic adjustment and hierarchical control"for soft rock tunnels is proposed for Chengdu Lanzhou Railway,focusing on optimizing the type,parameters of anchor bolt and construction machinery so as to make the anchor rod anchor quickly and bear load early.According to different large deformation levels,as the tunnel cross-section is gradually optimized,the maximum use of large cross-section excavation can not only reduce the disturbance of surrounding rock,but also reduce the impact of space constraints on the operation of long anchor bolts,so as to control the deformation of surrounding rock and improve the construction efficiency.The secondary lining is used as a safety reserve and is constructed after the initial support deformation is stable to ensure the long-term stability of the structure.The deformation of phyllite tunnel with high stress shows significant time-space effect.With the increase of large deformation level,the deformation proportion increases and the deformation time effect increases after inverted arch construction.Despite a certain discreteness of the tunnel deformation under different large deformation levels,the statistical samples obviously follow the normal distribution.Considering the measurement loss deformation,the interval estimation of 95%of the average value of normal distribution samples is taken as the limit value of tunnel reserved deformation.It is suggested that the reserved deformation of single track tunnel in slight large deformation section,medium large deformation section,serious large deformation section and extremely severe large deformation section of Chengdu Lanzhou railway is 10~20 cm,25~35 cm,35~45 cm and greater than 45 cm respectively,and the reserved deformation of double track tunnel in the corresponding sections is 20~30 cm,25~40 cm and 40~60 cm,and more than 60 cm respectively.Considering the large deformation classification and excavation method,the deformation control benchmark of high stress phyllite tunnel is established based on the tunnel construction process.As the tunnel deformation is monitored in real time through monitoring and measurement,timely measures can be taken to effectively prevent the clearance-intrusion induced by primary support.
作者
郭小龙
谭忠盛
喻渝
GUO Xiaolong;TAN Zhongsheng;YU Yu(School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China;China Railway Eryuan Engineering Group Co.Ltd,Chengdu 610031,China)
出处
《铁道学报》
EI
CAS
CSCD
北大核心
2022年第3期86-104,共19页
Journal of the China Railway Society
基金
铁道部科技研究开发计划(2010G018-C-1)
国家自然科学基金(51678034、51978041)。
关键词
隧道工程
软岩
变形特征
控制基准
控制技术
tunnel engineering
soft rock
deformation characteristics
control criteria
control technology
