Safety factor has a guiding significance in the slope stability analysis, and the finite element strength subtraction can get safety factor automatically according to the results of the calculation. But it also has deficiencies:firstly, the existing strength reduction program is compiled in the deflection;secondly, geotechnical material has two strength indexes of c and tanφ, if using the same reduc-tion factor, the two indexes in the process of reduction will fall by the same proportion, but it is not the case in the actual situation. Based on the finite element numerical calculations for obtaining the safety factors in FLAC3D, we discuss the accuracy of the self-made strength reduction program and the deflection of results. And by conducting a test according to the strength reduction deficiencies in the process of numerical calculations, we can get the correlation coefficient between c and tanφ, that is, we put forward a reasonable cor-rection coefficientβ, to amend the precision and bias. Verified by test, safety factors computed by the self-made strength reduction pro-gram show a ladder-like distribution, and have a certain relation with critical values of the defined safety factors. In addition, the cor-rection coefficient can better amend the deflection of the self-made strength reduction program and the error rate of safety factors is con-trolled with ± 0. 5%,which improve the precision of the results.%安全系数是边坡稳定性分析中的一个有指导意义的概念,强度折减法可根据计算结果自动获得安全系数.其不足之处在于:已有的自编强度折减程序偏差较大;岩土材料有2个强度指标黏聚力c与内摩擦角的正切值tanφ,若采用同一个折减系数,意味着在折减过程中这2个指标将按同一比例下降,但实际情况并非如此.本文以FLAC3D求解安全系数的过程为基础,探讨了自编强度折减程序的精度以及结果偏差问题;针对强度折减数值计算过程中的不足之处进行试验,得到c与tanφ之间的折减相关系数,由此提出一个较为合理的修正系数β以修正精度和偏差.经检验:自编强度折减程序求解的安全系数呈阶梯状规律分布,且与定义的安全系数上、下限之差的临界值呈一定关系;文中提出的修正系数能较好地修正自编强度折减程序的偏差,安全系数的误差率控制在±0.5%以内,提高了计算结果的精度.
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