层状岩体引水隧洞围岩稳定性数值模拟分析

Numerical Simulation Analysis of Surrounding Rock Stability of Water Diversion Tunnel in Layered Rock Mass

为研究不同产状下层状岩体引水隧洞在施工中围岩稳定性特征,以青海省引大济湟部分引水隧洞为例,建立不同岩层倾角下引水隧洞的三维有限元计算模型,计算不同倾角下层状岩体引水隧洞的围岩位移、塑性区范围、最大主应力及支护结构内力的变化规律。结果表明,拱顶沉降与底板隆起在岩层倾角为45°+φ/2(φ为岩体内摩擦角)时达到峰值;0°倾角时水平收敛最大;90°时塑性区和位移较大值分布在两侧直边墙顶部和底部,易发生边墙折断破坏;岩层倾角为0°、90°时最大主应力沿隧洞断面近似呈对称分布;30°~70°时最大值点随层理面平行方向移动。支护结构内力较大的围岩倾角是0°倾角,该角度上拱圈各点弯矩较大,应注意拱顶弯折破坏,不同岩层倾角下二衬计算安全系数均满足规范要求,在施工时应充分重视二衬施做前围岩的变形监控。

In order to study the stability characteristics of the surrounding rock in the construction of the diversion tunnels of layered rock mass under different occurrences,taking the part of the diversion tunnel in the Yindajihuang diversion tunnel of Qinghai Province as the engineering background,the three-dimensional finite element calculation model of the diversion tunnels was established under different rock strata inclination angles.The variation law of surrounding rock displacement,plastic zone range,maximum principal stress and internal force of supporting structure of water diversion tunnel of layered rock mass were calculated under different inclination angles.The results show that the settlement of the vault and the uplift of the floor reach the peak when the rock inclination angle is 45°+φ/2,and the horizontal convergence is the largest when the inclination angle is 0°.The larger values of the plastic zone and displacement are distributed on the top of the straight side walls on both sides at 90°.When the rock layer dip is 0°and 90°,the maximum principal stress is approximately symmetrically distributed along the tunnel section.When the rock layer dip is in the range of 30°and 70°,the maximum point moves parallel to the bedding plane.The inclination angle of the surrounding rock where the internal force of the supporting structure is larger is 0°.The bending moment at each point of the arch ring is larger at this angle.Attention should be paid to the bending failure of the vault.The calculated safety factors of the secondary lining under different rock inclination angles all meet the requirements of the specification.During the construction,full attention should be paid to the deformation monitoring of the surrounding rock before the construction of the second lining.