Foundation Force and Grouting Reinforcement of Central Separate Wall in Shallow Buried Multi-arch Tunnel
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摘要: 为研究浅埋连拱隧道中隔墙地基受力变形特征及基底注浆加固方法,依托云南省某拟建高速公路连拱隧道,采用MIDAS/GTS软件进行数值模拟计算和分析。研究结果表明:(1)在围岩较好、埋深较小时中隔墙基底压力分布随施工过程由“马鞍形”分布逐渐变为“钟形”分布,最大基底压力出现在先行洞衬砌浇筑后右侧墙趾处,中隔墙地基总体上处于隆起变形状态;(2)在围岩较差或埋深较大时中隔墙基底压力分布呈“马鞍形”分布,最大基底压力出现在后行洞二衬浇筑后中间偏右处,中隔墙地基总体上处于沉降变形状态;(3)通过数值分析得到不同埋深、地质条件下的连拱隧道中隔墙地基需要满足的承载力,并结合现行规范及前人研究成果,提出了中隔墙岩石地基加固前后地基承载力计算方法。研究成果可为连拱隧道的设计和施工提供参考。Abstract: In order to study the foundation deformation characteristics of the central separate wall of a shallow-buried multi-arch tunnel and the foundation grouting reinforcement method, the MIDAS/GTS software was used for numerical simulation calculation and analysis based on a proposed expressway multi-arch tunnel in Yunnan Province. The research results show that: (1) When the surrounding rock is good and the buried depth is small, the pressure distribution at the base of the central separate wall gradually changes from the “saddle-shaped” distribution to the “bell-shaped” distribution along with the construction process. The maximum base pressure appears at the toe of the right wall after the lining of the advance tunnel is poured. The foundation of the central separate wall is generally uplifted; (2) When the surrounding rock is poor or the buried depth is large, the pressure distribution at the base of the central separate wall is in a “saddle-shaped” distribution. The maximum base pressure appears at the middle right after the second lining of the rear tunnel is poured. The foundation of the central separate wall is generally in a state of settlement. (3) Through numerical analysis, the required bearing capacity of the partition wall foundation of the multi-arch tunnel under different burial depths and geological conditions is obtained. Combined with the current code and previous research results, a calculation method for the foundation bearing capacity of the central separate wall before and after the rock foundation reinforcement is proposed. The research results can provide reference for the design and construction of multi-arch tunnels.
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表 1 支护结构及小导管等计算参数
材料 尺寸/m γ/(kN·m−3) E/GPa μ 锚杆 0.025×0.005×3.5 78.5 210 0.3 中隔墙 1.3~1.6 23 30 0.25 中导洞初支 0.2 22.7 25.2 0.25 Ⅳ级围岩初支 0.25 22.7 25.2 0.25 Ⅳ级围岩二衬 0.45 23 30 0.25 Ⅴ级围岩初支 0.27 22.7 25.2 0.25 Ⅴ级围岩二衬 0.6 23 30 0.25 表 2 各级岩质围岩地层计算参数
地层 工况 γ/(kN·m−3) E/GPa μ φ/(°) c/MPa Ⅳ级围岩 低值 22.5 1.3 0.3 27 0.2 中值 23.5 3.65 0.325 33 0.45 高值 24.5 6 0.35 39 0.7 Ⅴ级围岩 低值 17 0.3 0.35 20 0.05 中值 19.75 0.7 0.4 23.5 0.125 高值 22.5 1.1 0.45 27 0.2 表 3 各工况连拱隧道中隔墙基底最大压力值
拱顶埋深/m 基底最大压力值/MPa Ⅳ级围岩 Ⅴ级围岩 φ=27°
c=200 kPa
E=1.3 GPaφ=33°
c=450 kPa
E=3.65 GPaφ=39°
c=700 kPa
E=6 GPaφ=20°
c=50 kPa
E=0.3 GPaφ=23.5°
c=125 kPa
E=0.7 GPaφ=27°
c=200 kPa
E=1.1 GPa10 1.338⑧ 1.251⑧ 1.196⑧ 1.539⑬ 1.302⑬ 1.144⑬ 20 1.844⑧ 1.886⑧ 1.903⑧ 2.110⑬ 1.880⑬ 1.584⑬ 30 1.648⑧ 1.748⑧ 1.828⑧ 2.529⑬ 2.119⑬ 1.772⑬ 40 1.819⑬ 1.785⑬ 1.844⑬ 3.206⑬ 2.225⑬ 1.609⑬ 50 2.213⑬ 2.175⑬ 2.217⑬ 2.799⑬ 2.407⑬ 1.593⑬ 注:带圈数字表示对应施工步骤编号。 表 4 对应坚硬程度的岩石饱和单轴抗压强度范围
岩石饱和单轴抗压强度frk/MPa 坚硬岩 较硬岩 较软岩 软岩 极软岩 >60 60~30 30~15 15~5 <5 表 5 岩石地基承载力特征值
${f}_{{\rm{ak}}}$ 岩石地基承载力特征值fak/MPa 岩体完整程度 坚硬岩 较硬岩 较软岩 软岩 极软岩 完整 >30 30~15 15~7.5 7.5~2.5 <2.5 较完整 >12 12~6 6~3 3~1 <1 较破碎 >6 6~3 3~1.5 1.5~0.5 <0.5 -
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