城际地铁大断面隧道三台阶法开挖参数优化研究

Study on Optimization of Excavation Parameters of Three Bench Method for Large Section Tunnel of Intercity Subway

根据超前地质预报揭露的实际地质及围岩情况,将南京市青龙山隧道开挖采用的原CRD工法调整为三台阶开挖工法施工。为确保工法调整后隧道围岩的稳定,采用FLAC 3D数值模拟方法,建立了不同开挖台阶高度和长度的隧道模型,分析了隧道开挖过程中围岩位移场、应力场和塑性区的变化规律,最终确定三台阶开挖工法的最优参数。研究结果表明:上台阶高度的增加促进了隧道围岩水平的收敛,但对拱顶下沉量影响较小;台阶开挖长度比台阶高度对围岩稳定性的影响更大,围岩位移和应力释放速度随开挖长度的增加而增大;为便于大型机械施工、保证隧道围岩的稳定性,确定上台阶高度为0.54H时的最佳开挖长度为7m。

According to the actual geological and surrounding rock conditions revealed by the advanced geological forecast,the original.CRD method used in the excavation of Qinglongshan tunnel in Nanjing was adjusted to three-step excavation method.In order to ensure the stability of the tunnel surrounding rock after the adjustment,a tunnel model with the different excavated bench height and length was established by the FLAC3D numerical simulation method to analyze the change law of the surrounding rock displacement field,stress field and plastic area during.tunnel excavation.Finally,the optimal parameters of the three-step excavation method was determined.The results show that the height increase of the upper benches promoted the horizontal convergence of the tunnel surrounding rock,but had less influence on sinking amount of the arch;The bench excavation length had a greater influence on the stability of the surrounding rock than the height.The speed of the surrounding rock displacement and stress release increased with the increase of the excavation length.The optimal excavation length is 7 m when the upper bench height is determined to be 0.54H so that the large-scale mechanized construction and the stability of the tunnel surrounding rock can be ensured.