大断面古土壤隧道围岩变形规律研究

Study on Deformation Law for Surrounding Rock of Large Section Ancient Soil Tunnel

古土壤形成时期、环境有别于黄土,因此,古土壤隧道围岩物理力学性质与黃土隧道存在一定差异。银西高铁早胜三号隧道作为国内首次穿越古土壤地层的长大隧道,为系统研究古土壤的物理力学性质及隧道穿越古土壤地层时关键施工技术研究提供了有利条件。本文以早胜三号古土壤隧道为研究背景,通过基础试验得到古土壤的物理力学性质,利用现场量测结果分析古土壤隧道的沉降变形收敛规律,然后通过数值模拟验证了现场监测结果。研究表明:古土壤具有密度大、比重大、抗剪强度较大和弱膨胀性的特点;隧道沉降变形分为快速增长阶段、持续增长阶段、平稳阶段,沉降主要集中在上台阶拱顶位置;围岩收敛主要集中在拱脚附近,且随着测点距拱脚位置的减小,收敛值逐渐扩大;同时,三台阶七步施工工法是造成左右围岩收敛值不同的主要原因;针对收敛主要集中在拱脚位置这一现象,建议进行仰拱曲率优化的研究。

The formation period and environment of paleosol are different from loess, so the physical and mechanical properties of tunnel surrounding rock are different from those of long tunnel.The Zaosheng No.3 Tunnel of Yinchuan-Xi'an Highspeed Railway, as the first tunnel crossing the paleosol stratum in China, provides favorable conditions for the systematic study of the physical and mechanical properties of paleosoil and the key construction technology of the tunnel crossing the paleosol stratum.Based on the research background of Zaosheng No.3 Paleosol Tunnel, the physical and mechanical properties of paleosol are obtained through basic tests, and the convergence law of settlement and deformation of paleosol tunnels is analyzed by field measurement results.Then the field monitoring results are verified by numerical simulation.The results show that the paleosol has the characteristics of high density, large proportion, large shear strength and weak expansibility.The settlement of tunnel is divided into rapid growth stage, continuous growth stage, stationary stage, and the settlement mainly concentrates on the upper step vault position.The convergence of surrounding rock mainly concentrates near the arch foot, and the convergence value gradually enlarges with the decrease of the distance between the measuring point and the arch foot position.At the same time, the three-bench and seven-step construction method is the main reason for the difference of convergence value between left and right surrounding rocks.In view of the phenomenon that convergence mainly concentrates on the arch foot position, it is suggested to study the optimization of inverted arch curvature.