爆破施工下小净距隧道围岩稳定性分析

针对辽宁地区某公路隧道的地质情况和施工条件,重点讨论了小净距隧道爆破过程对施工中围岩应力、位移和间距的影响。提出采用有限元法研究小净距隧道爆破施工过程中每步开挖围岩的应力应变状况,以此优化设计方案。爆破荷载以均布压力荷载的形式垂直于洞壁方向作用在隧道洞壁上。结合本隧道台阶法开挖过程提取8个关键点应力应变值。模拟结果显示,开挖前期拱腰受力明显,此后边墙底部应力增长迅速,两洞的内侧边墙应力都普遍大于外侧边墙应力,而应变矢量和最大处主要集中在洞顶。中岩柱左侧的应力应变始终大于右侧说明开挖过程对先行洞侧的中岩柱扰动影响最大,同时左洞中台阶开挖完毕后中岩柱两侧位移差逐渐增大说明中岩柱有膨胀破环的趋势。

Stability Analysis on Surrounding Rock of Small Spacing Tunnel under Blasting Construction

Based on the geological and construction conditions of one road tunnel in Liaoning province, this paper discusses the influence of blasting construction of small spacing tunnel on surrounding rock stress, displacement and spacing. The finite element analysis method is used to study the surrounding rock stress and strain condition during each step of blasting construction of the small spacing tunnel and to make optimal design based on this study. The blasting load is perpendicular to the cave walls in the form of uniform pressure load action. According to the tunnel excavation process in the way of step method, this paper extracts stress-strain values at eight key points and diagrams have been drawn. The simulated results show that in the early time of excavation the maximum stress is mainly concentrated in the arch waist and then the stress of bottom wall develops rapidly. The stress-strain of inside wall is generally greater than that of the outside wall in both holes, and the top hole mainly gets the largest strain all the time. Both strain and stress of the middle rock at left side are larger than those at the right side which states there is more influence of the side at first hole on the middle rock pillars than that of others during the tunnel excavation process. At the same time, after the excavation of left hole at second step, the displacement difference between left and right side of middle rock pillars is gradually increasing, there is a trend of expansion and breakage for middle rock pillars.