高应力卸压槽深度对隧道围岩卸压效果的离散元ABAQUS数值模拟

ABAQUS numerical simulation study on the effect of high stress relief groove depth on the pressure relief of tunnel peripheral rock

为探究高应力环境下隧道开挖卸压槽的卸压效果及其参数优化问题,本研究借助离散元数值模拟软件ABAQUS,对隧道围岩开挖不同卸压槽深度条件下的卸压效果进行全面分析。结果表明,当开挖卸压槽深度较浅(即不超过隧道宽度的5%)时,对隧道围岩应力分布影响有限,开槽点附近位移程度较小,开槽侧隧道底角岩体呈现弹性特征,塑性变化不明显,底板和开槽点位移变化小,但拱腰、仰拱和拱顶位移随开槽深度增加而增大,导致局部应力增大,在开槽点附近区域尤其明显,该区域应力水平提升了约13.29%,对隧道围岩的稳定性不利。随着卸压槽深度增加,应力集中区域向槽端迁移并缩小,弹性状态逐渐过渡到塑性状态,导致永久变形。当开挖卸压槽至隧道宽度的15%时,应力集中区域接近极限,应力卸压幅度接近最大值(卸压应力降幅为97%),并且位移量的增幅还在上升,卸压槽底部部位弹性能量积聚,影响隧道稳定性。侧压系数增加导致应力分布不均,引发应力集中,严重影响结构的稳定性。当侧压系数为2.0时,位移变化和弹性能变化幅度均显著大于侧压系数为1.0时的情况。

In order to investigate the pressure relief effect of tunnel excavation and its parameter optimization under a high stress environment,this paper comprehensively analyzes the pressure relief effect under different depth conditions of the pressure-relief groove in tunnel rock excavation with the help of discrete element numerical simulation software ABAQUS.The results show that when the excavation depth of the pressure-relief groove is shallow(≤5%of the tunnel width),it has limited influence on the stress distribution of the tunnel surrounding rock,the displacement near the slotting point is small,and the rock body at the bottom corner of the tunnel on the slotting side shows elastic characteristics.The plastic change is not apparent,the bottom plate and slotting point displacement change are small,but the displacement of arch waist,elevation arch and arch top increases with the increase of slotting depth,which at this time leads to the increase of local stress,especially obvious in the area near the slotting point,the stress level in this area is elevated by about 13.29%,which is unfavorable to the stability of the two tunnel gangs.As the depth of the unloading slot increases,the stress concentration area migrates to the end of the slot and shrinks.The elastic state gradually transitions to plastic,leading to permanent deformation.When the unloading slot is excavated to 15%of the tunnel width,the stress concentration area is close to the limit,and the stress unloading amplitude is close to the maximum(unloading stress drop of 97%).The increase in displacement is still rising,and the bottom part of the unloading slot is where the elastic energy accumulates,affecting the tunnel's stability.The increase in lateral pressure coefficient leads to an increase in stress distribution.The increase in lateral pressure coefficient leads to uneven stress distribution and stress concentration,which seriously affects the stability of the structure.The magnitude of displacement change and elastic energy change are significantly larger at a lateral pressure coefficient of 2.0 than at a lateral pressure coefficient of 1.0.