基于大型机械化的隧道长步距施工优化

Tunnel Construction Optimization with Long Steplength Based on Large-scale Mechanization

现有规范规定的施工安全步距主要源于人工钻爆法隧道的工程经验与理论成果,难以与大型机械化设备相匹配,同时也制约了公路隧道机械化建造技术水平的发展。依托武深高速公路荷花隧道工程,提出了由三臂拱架安装机、全自动湿喷机械、自行式液压仰拱栈桥等组成的适用于Ⅲ级和Ⅳ级围岩的大型机械化设备配套方案,确定了各类机械设备施工所需的长步距。采用三维数值仿真技术对比分析了规范步距与大型机械化设备施工所需步距(简称大机步距),在2种工况下围岩的变形规律与塑性区分布特征,对大型机械化设备在所需步距施工后的围岩变形与结构受力特征进行现场监测。结果表明:采用大型机械化设备施工时,初支封闭成环步距≤55 m,仰拱步距≤93 m,二衬步距≤151 m,远超现有规范;相比规范步距数值工况,大机步距工况下的围岩沉降和隆起量值更大,但最大沉降值仍小于设备预留变形量;大型机械化设备在所提步距施工后,现场监测发现拱顶最大沉降值<15 mm,拱腰与边墙的水平收敛最大值分别小于12 mm和8 mm,均保持在设计允许范围之内,进一步验证了大型机械化设备在所优化长步距下的施工可行性与安全性。

The existing construction safety steplength regulations mainly stem from the engineering experience and theoretical achievements of manual drilling and blasting method tunnels,which are difficult to match with large-scale mechanized equipment,and also restrict the development of mechanized construction technology for highway tunnels.Based on the Wuhan-Shenzhen expressway lotus tunnel project,the large-scale mechanized equipment supporting scheme suitable for Class Ⅲ and Class Ⅳ surrounding rocks was proposed,which consisted of the three-arm arch installation machine,fully automatic wet spraying machine,selfpropelled hydraulic inverted arch bridge,etc.The required long steplengths for various mechanical equipment construction were determined.The three-dimensional numerical simulation technology was used to compare and analyze the deformation rules and plastic zone distribution characteristics of standard steplength and required steplength for large-scale mechanized equipment construction(referred to as large machine steplength)under two working conditions.Conduct on-site monitoring of the deformation of surrounding rock and structural stress characteristics of large-scale mechanized equipment after the required steplength construction.The result indicates that when using large-scale mechanized equipment for construction,the initial support enclosed loop steplength is not more than 55.0 m;the inverted arch steplength is not more than 93.0 m;and the second lining step length is not more than 151.0 m;far beyond existing specifications.Compared with the standard steplength numerical working condition,the surrounding rock settlement and uplift values under the large machine steplength working condition are larger,but the maximum settlement value is still smaller than the reserved deformation amount of equipment.After the construction with largescale mechanized equipment at the proposed steplength,it is found that at on-site monitoring,the maximum settlement value of arch crown is less than 15.0 mm;and the maximum horizontal convergence values of arch waist and side walls are less than 12.0 mm and 8.0 mm respectively,remaining within the design allowable range.This further verified the construction feasibility and safety of large-scale mechanized equipment under the optimized long steplength.