库尔勒隧道开挖掌子面稳定性研究

Research on Stability of Excavating Face of the Korla Tunnel

在砂质围岩地层和软弱破碎围岩中开挖隧道会引起围岩扰动卸荷并改变围岩应力状态,若变形控制不当,极易导致掌子面发生破坏。库尔勒隧道为典型的戈壁全风化砂岩浅埋隧道,下穿既有营业线,掘进施工难度大,技术复杂。采用离散元颗粒流软件PFC2D研究全断面法、双台阶法及三台阶法在库尔勒隧道开挖中的适用性,从而确定合理的开挖工法。研究结果表明:采用全断面法和双台阶法施工时,围岩变形控制能力差,塑性区分布面积较大,围岩易产生滑塌。三台阶法更适合开挖库尔勒隧道,仰拱施作后隧道衬砌结构的安全系数较大,结构内力较小。相关研究成果可为今后类似工程提供借鉴。

Tunnel excavation in sandy surrounding rock strata and soft fractured surrounding rock will cause disturbance and unloading of surrounding rock and change the state of stress distribution of surrounding rock.If the deformation is not controlled properly,it is very easy to cause damage to the tunnel face.Korla tunnel is a typical shallow buried tunnel in Gobi completely weathered sandstone.It crosses the existing business line,which is difficult to excavate and complex in technology.The discrete particles flow software PFC2D is used to study the applicability of the full face method,double-step method,three-step method in the Korla tunnel excavation,so as to determine the reasonable excavation method.It is found that when using the full face and double-step methods in the excavation,the deformation control of the surrounding rock is bad,the distribution area of the plastic area is large,and the surrounding rock is easily collapsed.The three-step method is more suitable to excavate the Korla tunnel,the safety factor of the tunnel lining structure after inverted arch construction is bigger,and the internal force of the structure is smaller.The relevant research results can provide reference for similar projects in the future.