条间力分布对Sarma法条间强度参数及安全系数影响分析

Influence of the inter-slice force distribution on the strength parameters and safety factors of Sarma’s method

Sarma法作为极限平衡法的一种,可以用来评价各种类型滑坡稳定性。通常情况下将各岩土层强度参数的加权平均值作为等效的强度参数,分别根据条块间正应力的分布为三角形、平行四边形、梯形推导出相应的等效条间强度参数。将各自强度参数取值对安全系数的影响进行比较,分析条间力分布对条间强度参数取值和安全系数的影响。结果表明:1)条块间等效内摩擦角与条块间法向压力的分布有关;2)随着岩土强度参数差异的增大,条间力的分布对安全系数有一定影响,条间力三角形分布对安全系数的影响最小;3)与传统的条间强度参数取值相比,三角形分布时的安全系数偏高,四边形分布时的安全系数相等,梯形分布时的安全系数偏低,而取数值平均时的结果相近;4)随着上部岩土层内摩擦角的减小,各种分布得到的安全系数均呈下降趋势,但三角形分布时的结果所受影响最小。

The paper is to devote itself to the analysis of the corresponding impacting force on the safety factors exerted by the strength parameters through comparison and the influence of the slice interface distribution on the values of the strength parameters and the safety factors. As a category of the limit equilibrium methods,Sarma method serves as a tool for evaluating the various items concerning the stability of the rock slope stability. It is common sense that the weighted average value of the strength parameters of each layer can be used as equivalent strength parameters. The corresponding equivalent strength parameters of the slice interface can be derived from the distribution of the normal pressure along the slice interface into those as triangular,quadrilateral,trapezoidal,respectively,in this paper. Its corresponding impacts on the safety factor can be exerted by the strength parameters through comparison,and the influence of the slice interface distribution on the values of the strength parameters and the safety factors have also been analyzed. The results demonstrate the conclusions as shown below: First of all,the equivalent internal friction angles of slice interfaces can be related to the normal pressure distribution of the slice interfaces. Furthermore,with the mushrooming variation of the rock strength parameters,the distribution of the slice interfaces tend to exercise certain impacts of their corresponding interfaces on the safety factors,among which the triangular distribution of the slice interfaces may exert the minimalist ones. In addition,as compared with the traditional strength parameters,the triangular distribution reaps a high safety factor,whereas the quadrilateral distribution tends to possess the same answer,but the safety factor of the trapezoidal distribution tends to be lower,with the results of numerical average turning out to be balanced against each other. Eventually,with the reduction of the angular friction at the upper layer,the safety coefficient of all kinds of distribution may bring about a downward trend,with the effect of triangular distribution,though it is rather weak. However,in general,the geotechnical parameters turn out to be of great importance in the slope stability analysis. And,therefore,when Sarma method is adopted to calculate the safety factor of the slopes,the impact of the rock and soil layer on the inter slice force ought to be paid enough attention,for it ought to have come certain impact on the heaviest safety factor.