摘要
为探究中岩柱厚度小于2 m深埋超小净距隧道先行洞未施作二次衬砌时的近接施工力学特性,通过数值模拟、现场试验等方法,研究超小净距隧道近接施工围岩变形和支护结构受力特征。结果表明:(1)先行洞未施作二次衬砌时开挖后行洞,近接施工影响显著,因后行洞施工引起的先行洞围岩变形约占其总变形量的43%;后行洞开挖使得先行洞初支变形和内力呈现明显的偏压效应,即靠近中岩柱侧收敛变形和结构内力增幅远大于外侧。(2)初支钢拱架受力大致可分4个阶段:先行洞开挖影响段、中期稳定段、后行洞近接开挖影响段以及后期稳定段。施工过程中先行洞左右拱脚和仰拱部位存在较大拉应力,应重点关注。(3)先行洞仅施作初支情况下开挖后行洞,将初支变形和内力作为必测项目,可动态掌握其变化规律,及时采取控制措施,保障施工安全,避免后行洞爆破对先行洞二次衬砌造成结构损伤。
In order to investigate the mechanical characteristics of close construction of the tunnel with the thickness of medium rock column less than 2 m without secondary lining,the deformation of surrounding rock and the stress characteristics of supporting structure of the close construction of ultra-small clear distance tunnel are studied by numerical simulation and field test.The results show that:(1)when the first tunnel is not lined with secondary lining,the influence of adjacent construction is significant,and the deformation of surrounding rock of the first tunnel caused by the construction of the second tunnel accounts for 43%of the total deformation;the excavation of the rear tunnel causes the deformation and internal force of the first branch of the front tunnel to show obvious bias effect,that is,the convergence deformation and the increase of structural internal force near the middle rock column are much larger than those on the outside.(2)The stress of the initial steel arch can be roughly divided into four stages:the excavation influence section of the first tunnel,the middle stable section,the excavation influence section of the rear tunnel and the late stable section.During the construction process,there are large tensile stresses in the left and right arch feet and invert parts of the first tunnel,which should be paid attention to during construction.(3)The deformation and internal force of the initial branch are taken as the necessary items to be measured when the first tunnel is only used for primary support.The change law of the deformation and internal force of the initial branch are grasped dynamically and the control measures are taken in time to ensure the construction safety and avoid the damage of the secondary lining structure of the first tunnel by blasting of the rear tunnel.
作者
居国防
JU Guofang(China Railway Construction Kunlun Investment Group Co.Ltd.,Chengdu Sichuan 610040,China)
出处
《铁道建筑技术》
2024年第2期41-45,共5页
Railway Construction Technology
基金
国家自然科学基金资助项目(52378425)
中铁建昆仑投资集团有限公司科技研发项目(202201)。
关键词
超小净距隧道
近接施工
力学特性
数值模拟
现场试验
偏压效应
ultra-small clear distance tunnel
close construction
mechanical characteristics
numerical simulation
field test
bias effect
