不同倾角层状围岩隧道开挖松动圈的范围与分布

Range and Distribution of Loose Circle of Layered Surrounding Rock with Different Inclinations While Tunnel Excavation

层状围岩隧道在施工扰动下极易出现拱部严重超挖、掉块、离层、弯折、坍塌等工程问题,快速准确地确定围岩松动圈的范围和分布规律,对选择合理的支护设计参数以及消除安全隐患十分重要。以延安安塞经志丹至吴起高速公路大梁峁隧道为工程依托,采用离散元软件UDEC对岩层倾角分别为0°,15°,30°,45°,60°,75°和90°的层状围岩隧道开挖过程进行数值模拟,分析围岩松动圈的范围及分布规律。结果表明:岩层倾角为0°(水平)时,围岩松动圈范围最大,且出现在隧道拱顶处,松动圈范围为1.6~2.6 m;岩层倾角为0°和90°时,围岩松动圈沿隧道轴线对称分布;岩层倾角为30°,45°,60°,75°时,围岩松动圈呈不对称分布,且存在偏压现象。

Under the disturbance of construction,layered surrounding rock tunnels are prone to serious overexcavation of arch,block falling,separation,bending,collapse and other engineering problems. It is very important to quickly and accurately determine the range and distribution law of surrounding rock loose circle for selecting reasonable support design parameters and eliminating potential safety hazards. Taking the Daliangya Tunnel of Yan..an Ansai-Zhidan-Wuqi expressway as the engineering example,the excavation process of layered surrounding rock tunnels with inclination of 0°,15°,30°,45°,60°,75° and 90° were simulated by using the discrete element software UDEC,and the range and distribution law of surrounding rock loose circle were analyzed. The results show that when the strata inclination is 0°(horizontal),the loose circle of surrounding rock is the largest,which appears at the vault of tunnel, and the loose zone is 1.6~2.6 m. When the strata inclination is 0° and 90°,the loose circle of surrounding rock distributes symmetrically along the tunnel axis. When the strata inclination is 30°,45°,60° and 75°,the loose circle of surrounding rock is asymmetrically distributed,and there exists bias-pressure phenomenon.