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柱状节理条件下地形偏压小近距隧道施工,极易引起中夹岩柱的失稳,一直是工程界和学术界关注的问题。该文结合正在修建的石家庄市曹家庄公路隧道,采用离散元软件UDEC,模拟柱状节理特性下小净距隧道开挖,研究隧道失稳模式以及中夹岩柱的稳定性。数值分析结果表明:中夹岩柱有发生倾覆、旋转失稳的趋势,中夹岩岩柱深埋侧先发生滑移破坏,右侧出现旋转倾覆性失稳,最终岩柱呈现整体失稳贯通趋势。随着岩柱倾覆性失稳过程的发展,最终演化为整个隧道坍塌。锚杆发挥“销钉”作用,可增大层间节理剪切刚度,抑制中夹岩柱节理面,从而提高小净距隧道整体稳定性。
Under the condition of columnar joints, the construction of small-distance terrain bias tunnels can easily lead to the instability of the middle-column rock columns, which has always been a concern in engineering and academia. Combined with the construction of the Caojiazhuang highway tunnel in Shijiazhuang, this paper uses the discrete element software UDEC to simulate the tunnel excavation with small spacing under the characteristics of columnar joints to study the tunnel instability mode and the stability of the rock columns in the middle. The results of numerical analysis show that there is a tendency of overturning and rotation instability in the middle-column rock column, slip-failure occurs first in the deep-buried side of the middle-column rock-column, and rotation capsizes instability on the right side, trend. With the development of the rock column overturning instability process, eventually the whole tunnel collapses. Bolt play “Pin ” role, can increase the shear stiffness of the joints between layers, inhibit the rock column joint surface in order to improve the overall stability of small clear distance tunnel.