Sarma法在不同方位地震力下的计算研究

REVISED OF SARMA METHOD FOR DIFFERENT DIRECTIONS OF SEISMIC FORCE

Sarma法是计算边坡和堤坝稳定性分析广泛应用的方法,但在构建平衡方程时假设地震力方向为水平方向,未能考虑不同方位地震力对临界地震系数和边坡稳定系数的影响。为了研究临界地震系数和稳定系数在不同方位地震力下分布规律,本文在原Sarma的基础上,假设地震力非水平方向,在任意角度上尝试给出推导公式,并引入平均值对临界地震系数进行迭代求解。再求出临界地震系数对应的边坡稳定系数值后,可以得到地震力方向与临界地震系数和边坡稳定性系数的关系,临界地震系数最小值所代表的地震力方位作为用于边坡稳定性分析。经分析,临界地震系数极小值所代表的地震力方向不一定是指向坡外的水平方向;修正后临界地震系数极小值代表着边坡所能承受最小地震力的情况;同时求出的边坡稳定系数和原Sarma求出的边坡稳定系数相比误差不大,说明在假设地震力方位时,任意方位都可求解出准确的边坡稳定系数。

The Sarma method is widely used to calculate the slope and embankment stability analysis. But the method assumes the horizontal direction as seismic force direction. So it does not consider the impact of the different directions of seismic force. In order to study the critical seismic coefficient and stability factor in different directions under the distribution of seismic forces, this paper, based on the traditional Sarma, assumes that non-horizontal seismic force, at any given positions of seismic force, and try to derive the formula. And the mean value is ＂introduced to iteration when deal with the result of critical seismic coefficient. Examples are used to show the relationship among the directions of seismic force and the slope stability factor. After solving the minimum critical seismic coefficient, the represent angle of the minimum critical seismic coefficient is the angle of the smallest seismic force. On this point of the smallest seismic force, the stability analysis is gained in two classical examples. The analyses of the two examples derive the minimum value at last. Through the analysis, on the one hand, the direction of seismic forces represented by the minimum value is not necessarily pointing the outside horizontal direction. On the other hand, the corrected minimum critical seismic coefficient represents the authentic status that the smallest seismic force can be withstood by slope. Last but not the least, there is no sharp contrast between the calculated slope stability factor and the original slope stability factor. That is to say, when assuming the direction of seismic force, there will be no inaccuracy of assuming any position of the seismic force to calculate the valid slope stability factor.