奥陶系浅变质板岩地层半山隧道坍塌成因分析与处治

Causes and treatment method of collapse of Banshan tunnel in ordovician low-metamorphic slate stratum

由于板岩地层的断层破碎带较多,隧道穿越板岩地层时极易发生塌方事故。通过对半山隧道塌方的调查,研究奥陶系浅变质板岩隧道塌方的原因,在此基础上提出塌方的处治方案,结果表明:由于节理密集带走向和隧道走向夹角较小,形成不利结构面组合并斜穿隧道,隧道开挖极易造成大面积塌方,是产生塌方的基本原因;拱顶脱空严重,块石堆积重力超过初期支护支撑强度导致开裂,是产生塌方的直接原因。提出优化超前注浆及超前长管棚的施工方案,并采用三台阶预留核心土法进行开挖。按照处治方案进行施工,效果良好,可为类似工程塌方处理提供借鉴。

Because of the fault fracture zone in slate stratum,collapse may occur when tunnels are passing through slate strata.The collapse of the Banshan tunnel and the causes of the collapse was analyzed,and the solution to this accident was pointed out.It was concluded that: the angle between the joint density area and the tunnel direction was relatively small,which formed unfavorable structure for the tunnel.The excavation of the tunnel led to collapse in large scale,and this was the cause of collapse.When the dome disengaged,the supporting structure can not bear the gravity of the stacked stons.Then the collapse may occur because of this; A optimized and advanced construction program with grouting and long pipe roof was proposed,and the three-step Core Soil Reservation was used for excavation.During the construction under the guidance of the treatment,no accident occurred,which would provide reference for similar collapse accident in future.