钻爆法隧道机械化施工二衬支护时机优化方法

Optimization Method for Installation Timing of Secondary Lining in Mechanized Tunnel Construction Using Drilling and Blasting Method

近年来中国钻爆法隧道大力倡导机械化全工序建造,这种机械装备集成化的现代施工模式虽可有效提升掘进效率,但超长的机械装备作业线布设距离将会严重滞后二次衬砌支护时机,对软弱破碎岩层的围岩-支护结构稳定性造成威胁。通过调研隧道设计、施工规范关于确定二衬支护时机的相关原则及控制指标,梳理机械化全工序施工的作业线布设方案,提出了钻爆法隧道机械化施工背景下二衬支护时机的动态优化方法,综合围岩弹塑性本构模型,以及喷射混凝土、钢架、锚杆、二次衬砌本构模型,建立了围岩-支护结构相互作用全历程解析方法用于求解承载极限比、荷载分担比,最后计算分析了围岩安全系数的分布规律。结果表明:通过算例分析验证了提出的机械化施工二衬支护时机动态优化方法的有效性;不同强化的初支方案对应了80~120 m的机械装备作业线布设距离(二衬最晚支护时机),且二次衬砌可分担7%~13%的围岩荷载;80、100、120 m机械装备作业线布设距离对应的初支方案下,围岩整体安全系数分别为1.19、1.30、1.26,均满足安全控制基准。

In recent years,China has vigorously advocated the construction of mechanized full-process tunnels using drilling and blasting methods.Although this modern construction mode of integrated mechanical equipment can effectively improve excavation efficiency,the overlong distance of mechanical equipment operation lines will seriously delay the timing of the secondary lining support,posing a threat to the stability of the surrounding rock support structure in weak and fractured rock layers.By investigating the relevant principles and control indicators for determining the timing of secondary lining support in tunnel design and construction specifications and sorting out the layout plan of the entire mechanized construction process,a dynamic optimization method for the timing of secondary lining support under the background of mechanized tunnel construction using the drilling and blasting method is proposed.This method integrates the elastic-plastic constitutive model of the surrounding rock,as well as the constitutive models of sprayed concrete,steel arch,anchor rod,and secondary lining.A complete history of the analytical method for the interaction between the surrounding rock and supporting structure is established to solve the bearing limit ratio and load sharing ratio.Finally,the distribution law of the safety factor of the surrounding rock was calculated and analyzed.The results indicate that the effectiveness of the proposed dynamic optimization method for the timing of secondary lining support in mechanized construction has been verified through case analysis:Different reinforced initial support schemes corresponding to a distance of 80 to 120 m for the deployment of mechanical equipment operation lines(the latest support time for secondary lining),and the secondary lining can share 7%to 13%of the surrounding rock load;the overall safety factors of the surrounding rock under the initial support scheme corresponding to the arrangement distances of 80,100,and 120 m mechanical equipment operation lines are 1.19,1.30,and 1.26,respectively,which meet the safety control benchmark.