软岩隧道浅埋段围岩全位移空间分布特征研究

Spatial Distribution Characteristics of the Full Displacement of Surrounding Rock of a Shallow-Buried Tunnel Section in Soft Rock

围岩位移信息的收集对指导新奥法隧道施工具有重要意义。在各种因素制约下,围岩位移信息采集不可避免存在损失位移。文章依托阿拉坦隧道工程实例,以现场实测全位移数据为基础,确定了各施工阶段的围岩应力释放率,并在此基础上,对隧道浅埋洞口段地表与拱部围岩的全位移变化规律进行了三维数值分析。结果表明:隧道开挖过程中,地表测点竖向位移最大为33 mm,与实测结果基本一致,且地表测点竖向位移远大于水平位移,竖向损失位移比例占围岩总位移量的比例高达42.86%;隧道拱顶围岩竖向位移计算值为60 mm,与现场实测结果基本一致,隧道拱部围岩不同方向的损失位移所占全位移的比例不同,水平方向约为21.42%,竖向高达40%以上;掌子面通过监测断面前后约1.0倍洞径范围内围岩变形速率较大,在此区间,围岩竖向位移发生量约占总沉降量的70%。

Information collection for surrounding rock displacement is important for guiding tunnel construction with NATM. Loss of displacement information due to restriction of various factors is inevitable. Based on site-measured data of full displacement in the Alatan tunnel, the release rate of surrounding rock stress at various construction stages is determined, and a 3D numerical analysis of the variation law of the full displacement at the ground surface of a shallow portal section and surrounding rock at the tunnel crown is performed. The results indicate that： 1） the maximum vertical displacement at the surface, measuring 33 mm during tunnel construction, conforms to the measured data, while the vertical displacement at the surface measuring point is far larger than that of the horizontal displacement, and the vertical displacement loss is 42.86% of the total displacement of the surrounding rock; 2） the calculated vertical displacement of the surrounding rock at the tunnel crown is 60 mm, which basically conforms to the site-measured data; 3） the percentages of displacement loss of the surrounding rock at the crown are different in different directions, with 21.42% in the horizontal direction and more than 40% in the vertical direction; and 4） the deformation rate is relatively large-within the scope of 1.0 times the tunnel diameter before and after it passes through the monitoring section-with the vertical displacement being 70% of the total settlement.