﻿ 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

# 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

Abstract: 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.

1. 引言

G25长深高速杭州奇坑隧道进口段处于IV级凝灰岩，采用上下台阶法施工。隧道断面超大(大于150平米)，围岩软弱，大变形风险巨大，给工程安全带来极大挑战。因此，正确判断隧道洞周变形发展趋势，合理确定台阶步长和二衬施筑时机，对于确保安全，十分重要。

2. 工程概况

2.1. 地质概况和支护情况

Figure 1. The cross-section and profile of tunneling

2.2. 现场监测

Figure 2. Longitudinal geological profile

Table 1. Physical and mechanical properties of tuff

Figure 3. Layout of monitoring point for convergence measurement

Figure 4. Curve of crown settlement vs. time

Figure 5. Curve of convergence vs. time at upper bench

Figure 6. Curve of convergence vs. time at lower bench

3. 中风化凝灰岩流变模型

Figure 7. Two rheological models for tuff

${\epsilon }_{ij}=\frac{{\sigma }_{m}^{0}}{3K}\cdot {\delta }_{ij}+\frac{{s}_{ij}^{0}}{2{G}_{H}}+\frac{{s}_{ij}^{0}}{2{G}_{1}}\left[1-\mathrm{exp}\left(-\frac{{G}_{1}}{{\eta }_{1}}t\right)\right]\text{ }\left(i,j=1,2,3\right)$ (1)

Table 2. Physical and mechanical properties of the H-K rheological model of tuff

4. 三维有限元数值模拟

4.1. 有限元计算模型

Table 3. Physical and mechanical properties of the materials of primary lining

Figure 8. 3D-FEM discretized grid model

4.2. 有限元计算结果

4.2.1. 上台阶开挖的位移随时间变化情况

Figure 9. Displacement cloud on the 1st day of the excavation of top heading

Table 4. Displacements vs. time after the excavation of top heading

4.2.2. 下台阶开挖的位移随时间变化情况

Figure 10. Displacement cloud on the 15th day of the excavation of top heading

Table 5. Displacements vs. time after the excavation of the lower bench

4.2.3. 计算结果分析

5. 现场监测反馈分析

Figure 11. Displacement cloud on the 1st day of excavation of the lower bench

Figure 12. Displacement cloud on the 22nd day of excavation of the lower bench

Figure 13. Comparison between measurement and calculation of crown settlement-time curves

Figure 14. Comparison between measurement and calculation of convergence-time curves at the top heading

Figure 15. Comparison between measurement and calculation of convergence-time curves at the lower bench

6. 结论

1) 凝灰岩是蠕变特性显著的软岩，采用H-K流变模型可以很好地体现凝灰岩的稳态蠕变特征，以此进行三维有限元数值模拟和隧道变形预测，计算结果和现场实测结果十分吻合，对指导现场施工发挥了重要作用；

2) H-K流变模型的三个主要参数是随岩体开挖和支护施筑进程而不断发生变化的，采用有限元进行数值模拟时必须随围岩状况不断进行调整修正。本文采用拱顶沉降和上、下台阶收敛变形的现场实测结果进行三参数反演，实践证明这是实时修正流变模型参数的很有效的方法；

3) 本研究发现有限元计算结果对于三参数的敏感程度依次为胡克体弹性模量EH，开尔文体的弹性模量E1，开尔文体的粘滞系数η1

[1] 李习平, 阳军生, 王立川, 等. 三联隧道凝灰岩流变试验及其本构模型研究[J]. 铁道科学与工程学报, 2015, 12(1): 137-144.

[2] 杨英. 大丽铁路碎裂玄武岩夹凝灰岩型隧道特征及施工对策[J]. 铁道工程学报, 2007, 24(12): 64-68.

[3] 李习平. 凝灰岩地层大断面隧道围岩流变特性及变形控制研究[D]: [硕士学位论文]. 长沙: 中南大学, 2013.

[4] 熊含威. 凝灰岩区隧道二衬支护时机对结构安全性影响研究[D]: [硕士学位论文]. 重庆: 重庆交通大学, 2018.

[5] 黄俊. 成兰铁路某隧道软弱围岩变形特征及支护时机研究[D]: [硕士学位论文]. 成都: 成都理工大学, 2019.

[6] 刘城. 基于监测数据分析的隧道围岩稳定性研究[D]: [硕士学位论文]. 西安: 长安大学, 2016.

[7] 孙钧, 汪炳鑑. 地下结构有限元法解析[M]. 上海: 同济大学出版社, 1988: 104-105.

[8] 王怡, 王芝银, 韩冰. 岩石三轴蠕变试验粘弹性解析及参数识别[J]. 力学与实践, 2008, 30(3): 24-27.

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