Softening Effect and Control Measures of Surrounding Rock in Deep Buried Saturated Loess Tunnel
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摘要: 黄土隧道在地下水作用下围岩会发生不同程度软化，强度大幅度减弱，给隧道设计施工带来许多困难。依托陇东某黄土隧道，设置不同软化程度，利用有限元数值模拟软件对不同围岩软化程度下隧道围岩变形和衬砌结构的受力变化规律进行计算分析，同时对围岩软化后现场加固措施以及扩大拱脚的衬砌结构进行对比分析，结果表明：深埋黄土隧道强软化后，拱顶沉降增大了271%，拱底隆起增大了283%，水平收敛增大了205%，初支最大主应力增大了107%，其最不利受力位置出现在拱肩处；采用两种加固措施以及扩大拱脚后，围岩竖向位移减小5.10%～77.81%，初期支护最大主应力减小17.7%～46.5%，由加固处治效果可以看出，锁脚钢管桩加固仅对拱脚围岩变形及衬砌受力有所改善，但效果不明显；衬砌结构采用扩大拱脚可以较好地控制衬砌结构的变形及受力，且施工难度小，成本低；帷幕注浆加固对于饱和黄土隧道围岩软化后的变形及支护结构受力改善效果最佳。Abstract: Under the action of groundwater, the surrounding rock of a loess tunnel will undergo varying degrees of softening, greatly weakening its strength, which brings many difficulties to the design and construction of the tunnel. Based on a loess tunnel in Longdong, different degrees of softening were set up, and finite element numerical simulation software was used to calculate and analyze the deformation of the tunnel surrounding rock and the stress changes of lining structure under different degrees of rock softening. At the same time, a comparative analysis was conducted on the on-site reinforcement measures after the softening of the surrounding rock and the lining structure of the enlarged arch foot. The results show that after the strong softening of the deeply buried loess tunnel, the settlement of the arch top increased by 271%, the uplift of the arch bottom increased by 283%, the horizontal convergence increased by 205%, and the maximum principal stress of the initial support increased by 107%. The most unfavorable stress position appeared at the arch shoulder. After adopting two reinforcement measures and expanding the arch foot, the vertical displacement of the surrounding rock decreases by 5.1% to 77.81%, and the maximum principal stress of the initial support decreases by 17.7% to 46.5%. From the reinforcement effect, it can be seen that the locking foot steel pipe pile reinforcement only improves the deformation of the arch foot surrounding rock and the stress on the lining, but the effect is not significant. Using enlarged arch feet in the lining structure can effectively control the deformation and stress of the lining structure, and the construction difficulty is small and the cost is low. The curtain grouting reinforcement has the best effect on improving the deformation and supporting structure stress of saturated loess tunnel surrounding rock after softening.
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Key words:
- loess tunnel /
- softening of surrounding rock /
- on site reinforcement /
- enlarged arch foot
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表 1 隧道围岩参数表
结构
名称变形模量E0/
MPa含水率w/% 重度γ/(kN·m−3) 泊松比μ 黏聚力c/kPa 内摩擦角φ/（°） 未软化黄土 180 15 16 0.32 50 28 中软化黄土 100 20 18 0.36 35 27 强软化黄土 20 26 20 0.4 20 26 
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表 2 隧道支护结构参数表
结构名称 变形模量E0/MPa 重度γ/(kN·m−3) 泊松比μ 初支 28 23 0.2 二衬 30 23.5 0.2 钢拱架 2.1×105 78.5 0.2
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表 3 加固结构参数表
结构名称 变形模量E0/MPa 重度
γ/( kN·m−3)泊松比μ 黏聚力c/kPa 内摩擦角φ/（°） 帷幕注浆加固 1000 22 0.22 120 32 锁脚钢管桩 2.1×105 18 0.30
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表 4 位移变化率
加固措施 位移变化率/% 拱顶 拱肩 拱脚 拱底 水平收敛 锁脚钢管桩 5.10 10.07 28.08 16.26 8.41 扩大拱脚 29.64 20.25 62.95 19.08 26.27 帷幕注浆 66.82 61.19 77.81 66.65 71.31
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