风积沙地层仁布隧道进洞支护方案研究

Study on Entrance Support Plan of Renbu Tunnel in Aeolian Sand Stratum

风积沙地层隧道稳定性差,极易产生坍塌等灾害。为探索隧道洞口段穿越风积沙地层时有效的施工加固措施,保证安全快速施工,依托雅安至叶城国家高速公路拉萨至日喀则机场段仁布隧道洞口穿越厚层风积沙工程,结合风积沙地层特点对比分析常见的加固措施,总结一套风积沙地层条件下采用大管棚辅助、微型桩锁脚、旋喷桩加固地基及三台阶七步开挖法开挖施工隧道的进洞支护技术方案,成功实现隧道进洞。基于工程背景建立有限元模型,分析三台阶七步开挖结合管棚支护及地基处理措施对地表沉降、隧道收敛及拱顶沉降的控制效果,符合工程安全标准。

The stability of tunnels in aeolian sand strata is poor,which makes them prone to collapse and other disasters.To explore the effective construction and reinforcement measures when the tunnel portal section passes through the aeolian sand stratum and ensure safe and rapid construction,relying on the Renbu tunnel portal crossing the thick aeolian sand project in the Lhasa-Shigatse Airport section of the Ya’an-Yecheng national expressway,combined with the characteristics of the aeolian sand stratum,the common reinforcement measures are compared and analyzed,and a set of technical schemes of support for tunnel entrance under the aeolian sand stratum for tunnel excavation construction by using large pipe shed as auxiliary,micro-pile for locking foot,jet grouting pile for reinforcing foundation,together with three-bench seven-step excavation method is summarized,successfully realizing tunnel entry.Based on the engineering background,the finite element model was established to analyze the control effect of the three-bench seven-step excavation method combined with pipe roof support and foundation treatment measures on surface settlement,tunnel convergence,and vault settlement.The simulation results meet engineering safety standards.