不同主应力方向下隧洞围岩应力分布及塑性区特征分析

Stress distribution and plastic zone characteristics in surrounding rock of deep tunnel under different principal stress directions

隧洞开挖过程中主应力方向发生改变,造成围岩应力分布与塑性区随之产生变化,显著影响着隧洞围岩的稳定及支护。以椭圆形隧洞为例,模拟不同主应力方向下隧洞围岩的破坏,基于复变函数和强度准则建立不同主应力方向下不同深度的围岩应力解析解和塑性区模型,结果显示:主应力方向与椭圆形隧洞非共面时,围岩应力呈“斜哑铃状”分布,最大切向应力处于顶底部与侧帮之间的位置,且随着距临空面深度的增大,最大切向应力逐渐靠近水平主应力方向;随着主应力方向与隧洞夹角的增大,洞壁处的最大切向应力集中点由隧洞侧帮逐渐靠近隧洞顶底部,且洞壁破坏范围逐渐减小;随着主应力方向与隧洞夹角的增大,椭圆形隧洞围岩塑性区逐渐远离侧帮中心处,塑性区范围和最大深度逐渐减小。不同主应力方向下围岩塑性区最大深度所处位置平行或近似平行于水平主应力方向。

The change of principal stress in the process of tunnel excavation results in the change of stress distribution and plastic zone of surrounding rock,which significantly affects the stability and support of tunnel surrounding rock.In this paper,taking an elliptical tunnel as an example,the failure of surrounding rock under different principal stress directions was simulated.Based on complex variable functions and strength criterion,the analytical solution of surrounding rock stress under different principal stress directions and the plastic zone model were established.The results have shown that the maximum tangential stress is located between the top and bottom and the side wall,and with the increase of the depth from the free surface,the maximum tangential stress gradually approaches the direction of horizontal principal stress.With the increase of the angle between the principal stress direction and the tunnel,the concentration point of the maximum tangential stress at the free face gradually approaches the top and bottom of the tunnel.In addition,the damage region of the sidewall gradually decreases.As the angle between the principal stress direction and the tunnel increases,the plastic zone of the surrounding rock gradually moves away from the center of the sidewall,and the region and maximum depth of the plastic zone gradually decrease.Under different principal stress directions,the maximum depth of plastic zone is parallel or approximately parallel to the horizontal principal stress direction.