一种双折减法与经典强度折减法的关系

经典强度折减法的出发点是对强度值进行折减，进而导致对强度（准则）中的参数使用同一个折减系数。使边坡处于整体临界平衡状态的折减系数恰是边坡的强度储备安全系数。一些学者陆续提出了对黏聚力和内摩擦角采用不同折减系数的所谓双折减法，但尚无严格的理论依据。提出双折减法的出发点是对强度（准则）中的参数进行折减，或简称“强度参数折减”，这样可自然导致采用不同的折减系数，但此时已无法自动得到基于强度储备的安全系数。为此，提出了定义安全系数的新框架--基于参照边坡的安全系数定义，为双折减法建立了理论基础。将新提出的一种双折减法与经典强度折减法进行了比较，发现可以将经典强度折减法纳入该双折减法的计算过程，并从理论上证明了该双折减法的安全系数几乎总是小于经典强度折减法的安全系数，数值模拟实例也证实了这个结论。这表明，经典强度折减法有可能高估了边坡的安全性，建议的双折减法可作为边坡稳定分析的备选方法之一。

Comparing a new double reduction method to classic strength reduction method for slope stability analysis

In the classic strength reduction method (SRM), there is only one strength reduction parameter which can be proved to be equal to the definition of factor of safety (FOS) by strength reservation. Some double reduction methods (DRM), in which distinct reduction parameters are used for friction angle and cohesion force, have been presented by researchers. In this paper, a new basis is established to support the rationality of the double reduction methods, and also a specific definition of FOS is built for a recently presented DRM by the authors. A comparison is made between the DRM and the SRM through rigid mathematical proving, which shows that the FOS of the DRM is almost always smaller than that of the classic SRM. This conclusion is verified by four numerical examples. The research shows that the possibility that the classic strength reduction method (SRM) may overestimate the safety of a slope exists. It is advised that the presented DRM be adopted as an additional option in the slope stability evaluations although more application experience is expected.