复杂应力场中圆形隧洞偏应力场分布规律

Distribution Law of the Deviatoric Stress Field of Circular Tunnel Surrounding Rock in the Complex Stress Field

为了厘清深部圆形中导洞(设置于双向隧洞中间)围岩偏应力分布问题,结合岩石力学与摩尔-库仑屈服准则,推导平面三向应力场中圆形隧洞围岩主偏应力与塑性区半径解析解,研究不同工况下圆形隧洞围岩主偏应力的分布规律及塑性区边界处主偏应力的几何形态分布特征。结果表明:当隧洞所处的斜向应力场为竖向应力场0.5~1.0倍时,随着斜向应力场水平方位角α_(1)=α_(2)增加,径向1.0倍隧洞半径范围内顶底主偏应力在快速降低,腰部主偏应力在快速增加,径向1.0倍隧洞半径范围外隧洞围岩主偏应力先小幅下降后又逐渐增大,最终在围岩深部趋于某定值;隧洞围岩主偏应力对其塑性区形态分布影响显著,当斜向应力场水平方位角α_(1)=α_(2)为30°时,围岩塑性区形态分布较优,为圆形或椭圆形。

In order to clarify the problem of deviatoric stress distribution in the surrounding rock of the deep circular pilot tunnel(set in the middle of the bidirectional tunnel),based on rock mechanics and Mohr Coulomb yield criterion,the analytical solutions of surrounding rock deviatoric stress and plastic zone radius in the plane three-directional stress field were deduced.The deviatoric stress distribution law of surrounding rock for different working conditions and the distribution characteristics of the deviator stress at the boundary of surrounding rock plastic zone were studied.Results show that:when the oblique stress field of circular tunnel is 0.5~1.0 times of vertical stress field,with the increase of horizontal azimuth angleα_(1)=α_(2) of oblique stress field,the deviatoric stress at the top and bottom of tunnel decreases rapidly and the deviatoric stress at the waist increases rapidly within the range of 1.0 times tunnel radius.For the outside range of 1.0 times tunnel radius,the surrounding rock deviatoric stress firstly decreases slightly and then increases gradually with the increase of horizontal azimuth angle.The shaped distribution of surrounding rock plastic zone was significantly affected by its deviatoric stress.When the oblique stress field of middle pilot tunnelα_(1)=α_(2) is 30°,the shaped distribution of surrounding rock plastic zone is better,which is circular or elliptical.