多软弱夹层坝基混凝土重力坝加固效应评价方法研究

Study on Evaluation Method of Reinforcement Effect of Concrete Gravity Dam with Multi Weak Interlayer Foundation

各国现行规范均规定,在进行重力坝设计或安全鉴定时必须审查大坝沿建基面和坝基岩体内软弱结构面的抗滑稳定性,要求保证大坝不滑动且有必要的安全裕度.针对某一典型重力坝工程,推导了考虑加固措施影响的重力坝抗滑稳定计算公式,并结合预应力锚索加固监测数据,通过有限元模拟预应力锚索的加固效应,最后将刚体极限平衡法与基于场变量的强度折减法相结合评估该工程加固措施的有效性.研究结果表明:在采用有限元计算时,当折减系数增大至2.3时,坝踵及f_(1)夹层与F_(73)断层交界位置均产生了一定程度的屈服;当折减系数达到3.0时,f_(1)夹层形成整体贯通,有限元计算仍收敛;当折减系数达到3.05时,计算出现不收敛.与刚体极限平衡法的计算结果相比,基于场变量的强度折减法所得的抗滑稳定安全系数计算结果在允许误差5%范围之内,且均满足规范要求,验证了该工程除险加固措施的有效性.本研究可为类似预应力锚索加固重力坝工程提供参考依据.

According to current specifications of various countries,the anti-sliding stability of the dam along the foundation surface and the soft structural surface in the dam foundation rock must be reviewed to ensure the safety when designing or evaluating the gravity dam.For a typical gravity dam project,the anti-sliding stability calculation formula of the gravity dam considering the influence of reinforcement measures is derived firstly.Then the reinforcement effect of prestressed anchor cables is simulated by finite element method and compared with the reinforcement monitoring data of prestressed anchor cables.Finally,the effectiveness of the reinforcement measures of the project is evaluated by combining the rigid body limit equilibrium method with the strength reduction method based on field variables.The results show that when the reduction coefficient increases to 2.3,the dam heel and the interface between the interlayer and the F73 fault yields to some extent.When the reduction coefficient reaches 3.0,the interlayer is whole broken,and the finite element calculation still converges.When the reduction coefficient reaches 3.05,the calculation does not converge.Compared with the calculation results of the rigid body limit equilibrium method,the calculation results of anti-sliding stability safety factor obtained by strength reduction method based on field variables are within the allowable error of 5% and meet the requirements of the specification,which verifies the effectiveness of the reinforcement measures for the project.This study can provide reference for similar gravity dam projects strengthened with prestressed anchor cables.