摘要
深埋盾构隧道所受围岩压力主要为围岩挤压型大变形产生的形变压力,其主要特点是变形持续时间长且具有重复性,支护完成后围岩压力仍将持续增大,企图通过增加支护刚度来抑制围岩变形是不现实的,采用让压支护是解决问题的一个方向。同时,深部围岩赋存条件复杂,岩体结构复杂多变,盾构隧道穿越复合地层不可避免。以国内两座大埋深盾构煤矿斜井为背景,采用相似模型试验和有限元数值计算手段,对比分析不同复合地层条件下管片衬砌+可压缩层联合支护时管片衬砌的力学性能。研究结果表明:在模型正确建立且参数取值合理的前提下,有限元数值计算结果可以和相似模型试验结果很好的吻合。均一地层条件下可压缩层可使管片最大弯矩减小12.5%~19.9%,最大轴力减小14.2%。复合地层使管片弯矩量值和分布均产生明显变化,但对管片轴力的影响则不明显,管片弯矩对复合地层抗力更为敏感,而轴力对复合地层抗力不敏感。有可压缩层情况下,复合地层中管片内力分布更加均匀,轴力的变化不明显。复合地层相对厚度对管片最大正弯矩的影响较为稳定,对管片最大负弯矩影响显著,使其产生位置偏向相对较软一侧的地层,且相对厚度越大偏移越明显。"上硬下软"复合地层中管片弯矩更容易受地层相对刚度的影响。
The surrounding rock pressure of deep buried shield tunnels is mainly the deformation pressure produced by large extrusion type deformation of the surrounding rock. Its main feature is that the deformation lasts for a long time with repeatability. The pressure of the surrounding rock will keep increasing after the support is completed. Because it is unfeasible to restrain the deformation of surrounding rock by increasing the support rigidity, yieldable supports become a solution for the problem. Meanwhile, due to the complexity and variability of the surrounding rock condition and the rock mass structure, it is inevitable to pass through composite strata in shield tunnel construction. Based on the inclined shafts in two deep buried shield coal mines, comparison and analysis on the mechanical properties of segment linings with the segment lining + compressible layer combined supports in different composite stratum conditions are studied by means of similarity model tests and the finite element numerical method. The results indicate that the finite element method results are in good agreement with the experimental results when the model is correctly established and the parameter values are reasonable. Under the uniform formation condition, the compressible layer brings about 12.5%~19.9% decrease to the maximum bending moment and 14.2% decrease to the maximum axial force. The composite stratum causes obvious changes in the value and distribution of the segment bending moment, but has little effect on the segmental axial force,indicating that the bending moment is more sensitive to the resistance of the composite stratum while the axial force is relatively insensitive. With the compressible layer, the distribution of the segment internal force is more uniform in the composite stratum and there is little change in the axial force. Furthermore, the relative thickness of the composite stratum influences the maximum positive bending moment stably. It also greatly influences the maximum negative bending moment, causing deviation to the relative soft side of its generating position. The larger the relative thickness of the composite stratrum, the more obvious is the deviation. In an upper hard and lower soft composite stratum, the segment bending moment is more easily affected by the relative stiffness of the stratum.
引文
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