超前半闭合双导洞台阶法在富水大断面隧道中的应用

为解决用传统工法在富水大断面隧道不良地质段施工时出现的涌水、塌方等灾害,以云南省光山1号隧道为工程背景,通过工程地质调查和涌水、塌方机制分析,提出“超前半闭合双导洞台阶法”(简称“ASDP台阶法”)。用有限差分软件FLAC^3D对新工法的施工过程进行数值模拟。结合现场监测数据,发现右、左导洞开挖对拱顶、拱底竖向变形的“贡献”甚微,即使该工法提前开挖了导洞仰拱,但通过迅速施作工字钢形成半闭合结构,能够很好地控制土体卸荷带来的拱底隆起和隧道整体变形。采用ASDP台阶法后,光山1号隧道不良地质段最终得以顺利完成。ASDP台阶法工序衔接合理,进尺效率高,排水效果良好,造价低,可作为不良地质下富水大断面隧道施工的首选工法。

Application of Advanced Semi-closed Double Pilot Step Method in Water-rich Tunnel with Large Section

To tackle the problems of water inrush, collapse and other disasters in the construction of the unfavorable geological segment of water-rich large-sectional tunnel using traditional construction methods, we propose an advanced semi-closed double pilot step method (ASDP step method for short) based on engineering geological investigation and analysis on water inrush and collapse mechanism. Subsequently, we simulate the construction process of ASDP step method by using finite difference software FLAC^3D. In association with field monitoring data, we found that the excavation of the right and left pilots contributes little to the vertical deformation of the arch crown and the arch bottom. Even if the inverted arch of pilot is excavated in advance in this method, the arch bottom uplift and overall tunnel deformation caused by soil unloading can be well controlled by quickly applying I-beam to form a semi-closed structure. After adopting ASDP step method, we successfully completed the construction of unfavorable geological segment of Guangshan No.1 Tunnel. The ASDP step method is featured with reasonable connection among procedures, high footage efficiency, good drainage effect and low cost, thus can be used as the preferred method for the construction of water-rich large-sectional tunnel in unfavorable geology.