浅埋软弱围岩隧道施工塌方及处治措施研究

Research on Collapse and Treatment Measures for Shallowly Buried Weak Surrounding Rock Construction

针对云南武易高速公路丰收隧道施工过程中发生的塌方事故,分析了隧道大变形及塌方的成因,对浅埋偏压软弱围岩隧道三台阶法施工过程进行了三维精细化数值模拟。结果表明:软弱围岩、顺层及地形偏压、浅埋是隧道大变形及塌方的客观原因,施工不规范导致支护刚度不足、掌子面稳定性控制不力进一步加剧了隧道变形失稳,换拱则直接导致了隧道塌方;软弱围岩隧道开挖对掌子面前方岩体扰动范围达到3倍进尺,约80%的拱顶下沉发生在上台阶的开挖阶段;掘进宜采用短台阶,使初支及时封闭,锁脚锚杆打设最佳角度为45°,对围岩条件极差的区段可采用双侧壁导坑法施工;静力水准自动化监测系统可实现隧道沉降的实时监测,反馈指导施工。

The causes of tunnel deformation and collapse are analyzed in the context of the collapse accident that occurred during the construction of the Fengcai Tunnel of the Wuyi Expressway in Yunnan Province,and the threedimensional refined numerical simulation of the construction process of the three-stage method for shallowly buried partial pressure soft rock tunnel is presented.The results show that:the objective causes of the tunnel deformation and collapse are the weak surrounding rocks,the partial pressure of the cascade and topography,and the shallow burial;the lack of rigidity of the support due to irregular construction and the poor control of the stability of the palm face further aggravate the tunnel deformation and instability;the change of arch directly leads to the collapse of the tunnel;the excavation of the weak surrounding rocks disturbs the rock in front of the palm face up to 3 times of the footage,and about 80%of the sinking of the vault occurs in the upper step of the excavation stage;short steps should be used for excavation,so that the initial support can be closed in time,the best angle for locking anchors is 45°,and for sections with very poor rock conditions,the double sidewall guide pit method can be used;the static level automatic monitoring system can achieve real-time monitoring of tunnel settlement and provide feedback to guide construction.