为了解浅埋偏压黄土隧道洞口段支护结构的受力状况, 对刘家坪2#隧道洞口段围岩压力、钢架应力、喷射混凝土应力、纵向连接筋应力、锚杆轴力及拱部下沉进行施工监测, 并采用有限元法对隧道支护结构进行计算分析。结果表明:在浅埋偏压条件下, 黄土隧道拱部发生了平面偏移, 拱顶下沉量大于净空收敛量;围岩压力分布呈不对称猫耳状;钢拱架左侧轴力大于右侧轴力, 总体受力很大, 在支护体系中作用很明显;拱部和边墙喷射混凝土处于受压状态, 而底部多为拉应力;拱部系统锚杆对结构的稳定性作用不大, 而锁脚锚杆对结构的稳定性有一定的作用;纵向连接筋受力非常大, 对隧道整体的稳定性很有利;应取消黄土隧道洞口段系统锚杆, 采用由钢拱架、钢筋网、锁脚锚杆、喷射混凝土、纵向连接筋组合形成的初期支护结构。
Abstract
The dynamics measures on the structure of Liujiaping 2# Tunnel were taken to know the mechanics characteristic of the loess tunnel entrance in the shallow unsymmetrical loading sector, and the support structure of tunnel was analyzed using finite element analysis method. The content included surrounding rock pressure, steel arch stress, shotcrete stress, longitudinal link bar stress, anchor axial force and crown settlement measurement. The results show that surrounding rock pressure is not symmetrical. The tunnel arch produces plane migration, and the values of crown settlement is bigger than that of clearance convergence. The left of steel arch axial force is bigger than the right and whole forcing is big. So the steel arch has great effect on the structure. Stress of arch and side wall shotcrete is in pressure and the bottom is in tension. System anchors on the arch have little effect on the stability of structure, but foot anchors have much more effect. Longitudinal link bar stress is big and link bar has good effect on the stability of the tunnel. So the system rockbolts can be retracted in portal part of tunnel in loess, and primary support can take the system of steel arch, grillage, foot anchors, shotcrete and link bars.
关键词
隧道工程 /
黄土隧道 /
数值分析 /
力学特性 /
偏压 /
监测
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Key words
tunnel engineering /
loess tunnel /
numerical analysis /
mechanics characteristic /
unsymmetrical loading /
measure
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中图分类号：
U456
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脚注
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基金
国家西部交通建设科技项目(2007 318 812 68)
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