Short-term Undrained Analysis of Passive Instability of Shield Tunnel Excavation Face
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摘要: 当前对富水黏土地层中的盾构隧道开挖面被动失稳破坏模式的研究较少。为此，提出不排水效应下的盾构开挖面被动失稳破坏理论模型，分别对均质土和成层土工况下的极限支护力函数未知量进行分析，将结果拟合后给出了快速估算极限支护力的理论计算公式。通过对比数值计算结果与理论解析结果，进一步探讨了模型的适用性。结果表明：在浅埋情况下（C/D≤1.0），拱顶上部破坏区的边界近似竖直，与提出的破坏模式设想较为相符，随着埋深比的增大，破坏区对地表的影响也越来越小。Abstract: The construction environment of shield tunnel becomes more and more complex. However, there are few researches on passive instability failure modes of shield tunnel excavation face in water-rich clay stratum. A theoretical model of passive instability failure of shield excavation face under undrained effect was proposed. The unknown quantity of ultimate support force function was analyzed for homogeneous soil and layered soil respectively. After fitting the results, a theoretical calculation formula for rapid estimation of ultimate support force was given. Finally, the applicability of the model is further discussed by comparing the numerical results with the theoretical results. The results show that under the condition of shallow burial (C/D≤1.0), the boundary of the upper failure zone of the vault is approximately vertical, which is consistent with the proposed failure mode assumption. With the increase of buried depth ratio, the influence of the damaged area on the surface becomes less and less, and even the damaged area does not extend to the surface when buried deeply.
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图 6 不同
$(c_{\rm{u}}^{\min }/c_{\rm{u}}^0)$ 情况下Nc与${\displaystyle \sum _{j=1}^{n}({c}_{\rm{u}}^{j}{z}_{j}/{c}_{\rm{u}}^{0}D)}$ 关系
图 7 不同
${\displaystyle \sum _{j=1}^{n}({c}_{\rm{u}}^{j}{z}_{j}/{c}_{\rm{u}}^{0}D)}$ 情况下Nc与$(c_{\rm{u}}^{\min }/c_{\rm{u}}^0)$ 的关系
图 8 不同
$\gamma D/{c_{\rm{u}}}$ 情况下荷载参数$({\sigma _{\rm{T}}} - {\sigma _{\rm{s}}})/{c_{\rm{u}}}$ 与埋深比C/D的关系
图 9 不同C/D情况下荷载参数
$({\sigma _{\rm{T}}} - {\sigma _{\rm{s}}})/{c_{\rm{u}}}$ 与重度参数$\gamma D/{c_{\rm{u}}}$ 的关系表 1 不排水条件数值模拟的物理力学参数
工况 土层 饱和重度γ/(kN·m−3) 不排水抗剪强度cu/kPa 1 覆土层 γ1=18 $c_{\rm{u} }^1$=20 穿越层 γ0=18 $c_{\rm{u} }^2$=20 2 覆土层 γ1=19 $c_{\rm{u} }^0$=15 穿越层 γ0=18 $c_{\rm{u} }^1$=20 3 覆土层 γ1=19 $c_{\rm{u} }^2$=25 穿越层 γ0=18 $c_{\rm{u} }^0$=20 
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表 2 不同埋深比情况下解析解与数值解的对比
C/D FLAC3D/kPa 本文解析解/kPa 0.5 225 233.9 1 316.3 324.6 1.5 395 413.8 2 469 501.7 2.5 539 588.6 3 610 674.9
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