基于凝灰岩流变特性的隧道台阶法三维有限元数值模拟和监测反馈分析——以浙江奇坑隧道进口段施工方案比选为例

3D-FEM Numerical Simulation and Back Analysis of a Tunnel Excavated with Bench Method Considering Tuff’s Time-Dependency—A Case History: Study on the Intake Section of Qikeng Tunnel in Yuhang County, Zhejiang Province

凝灰岩是一种软岩,具有显著的流变特性。在凝灰岩山体中进行大跨度山岭隧道施工必须重视隧道大变形和变形发展持续时间长的问题,并采用科学的预测方法和合理的施工手段对可能的施工风险予以规避。基于现场监测资料的分析和文献调研,本文引入H-K弹–粘弹性流变模型描述凝灰岩稳定蠕变特征的方法,并采用三维有限元软件对浙江奇坑隧道进行了数值模拟计算和参数反演,研究表明基于岩体流变特性的数值模拟计算和现场监测反演可以很好地预测上下台阶法施工的洞周变形,可以为科学合理地制订开挖、支护和二衬施筑方案提供依据。

Tuff is a kind of soft rock with distinctive rheological characteristic. There are always many problems rising during construction such as significant magnitude and long enduring time of tunnel deformation. Therefore, it is very important to find a scientific prediction method and follow a reasonable construction route averting this risk. Based on site measurement and study of academic papers, this paper suggests that H-K rheological constitutive model be an ideal one to describe tuff’s time-dependency when analyzing the tunnel’s behavior using 3D FEM software, and presents a result of 3D-FEM numerical simulation and back analysis about the excavation of Qikeng tunnel, which is located in Zhejiang province. This study shows that numerical simulation, which is based on rheology, and back analysis, which is based on site measurements, can well forecast the displacement development of a tunnel with top heading and bench method and can provide with evidence for the decision making on which excavation method to choose, what primary lining to design and when to carry out second lining.