基于遗传算法和Bishop法,对工程实践中最为广泛应用的圆弧滑裂面提出了搜索临界滑移面及相应最小安全系数的方法。因为安全系数存在多个极小值,所以一般优化方法搜索边坡临界滑移面较为困难,而遗传算法能很好的处理多极值优化问题。传统的方法采用固定不变的上下界设计变量,这样会扩大搜索范围,同时产生许多不符合运动学许可条件的解。在分析时需把这些不符合条件的解剔除,将降低搜索的效率。对于这个问题若采用遗传算法,问题的约束条件变换为由动态的上下界设计变量决定,可缩小搜索范围,且不会产生不符合运动学许可条件的解,在合理的计算时间内临界滑移面能被高精度地搜索到。数值算例表明:所建立的基于遗传算法的岩土边坡稳定分析方法,是一种全局优化搜索算法,能够有效克服经典搜索方法易陷入局部极小值的缺点,其计算结果令人满意。
Based on genetic algorithm and Bishop's method, searching methods of circular sliding surface applied widely in engineering for the critical failure surface are presented and the minimal safety factor is located accordingly. The searching critical failure surface of a general soil slope is difficult as the objective function for the factor of safety is non-convex and multiple minimal exist in general, but genetic algorithm works well on optimization for multiple extremes. Traditional methods use constant upper and lower bounds of the design variables, which would enlarge searching band and create many unacceptable solutions to meet the requirements on kinematically acceptable mechanism. These solutions need be removed, which will cause efficiency loss for searching. For this problem, real-valued genetic algorithm is proposed and the constraints of the problem are transformed to the determination of the dynamic upper and lower bounds of the design variables. So, searching band is reduced and the efficiency for searching is improved. The critical failure surface can then be located with high precision with reasonable calculation time under the presented proposal. Numerical example shows that analyzing method of the slope stability based on the genetic algorithm is a global optimal procedure that can overcome the drawbacks of local optimum widely existing in classical searching methods. The analytical result is satisfactory.