基于LCM的水平成层边坡失稳判据

On the instability criteria for the plane-layered slope based on the limited curve method

强度折减法应用于边坡稳定性分析的关键是确定失稳判据,但目前尚无统一标准。基于极限曲线法(LCM),提出以滑移线场理论计算得到的边坡极限状态下的坡面曲线(简称极限稳定坡面)与原坡面相交于坡脚判断边坡处于极限状态的失稳判据。2个成层边坡算例计算结果表明,该失稳判据适用于强度折减法;将折减后使边坡处于极限状态的强度参数直接输入到FLAC2D 7.0,由边坡贯通区和位移确定临界滑裂面,其形状及在边坡中的位置与已有结论基本一致。相对于已有强度折减法,该方法实现了失稳判据的客观标准定量化,计算安全系数和确定临界滑裂面分开进行,确定临界滑裂面不需要优化搜索和迭代计算。

In this paper,the author is inclined to propose a new instability criterion for strengthening the reduction method based on the limited curve one.This new criterion is aimed to determine the slope stability by regulating the relative position between the slope contour curve(which has been worked out by the slip and slope linear field theory but in this paper it is referred to as the unified limit slope curve)to determine the slope stability.That is to say,the said slope should be here referred to as the slope intersect under the limited equilibrium state in accordance with the actual construction needed in a limited slope curve form.The calculation results of the layered slopes indicate that the relative position of the limited slope curve and the slope itself should be changing with the strength reduction factors.In the regard of the 2-layered slope,with the strength reduction factor increased from 1.0 to 1.1,the x11 should change from positive to zero(x11 represents the intersection abscissa between the limit slope curve and the slope bottom).What is more,in the regard to the 3-layered slope,with the strength reduction factor having been decreased from 1.0 to 0.587,the actual value of x11 should change from negative to zero.Therefore,based on the new instability criterion,the factors for the actual safety should be able to be worked out respectively equal to 1.1 and 0.587 versus 1.01 and 0.635 by the upper boundary or the limit approach of the rigid elements and the traditional instability criteria for the 2 and 3 layered slopes.In so doing,the relative error can only be reduced to merely 8.18%and 7.56%,respectively.Besides,the new instability criteria can also be applied for the strength reduction method of the layered slopes.The strength parameters of the slope under the limited state can be directly input into FLAC2 D 7.0.Hence,it would be possible to determine the critical slip surface shape and position by the plastic strain and displacement,which are actually the same conclusions as it were already coming into being.Thus,the method proposed here can also help to realize the objective quantification of the instability criteria.Besides,the calculation of the safety factor and the determination of the critical slip surface can also be regarded as the separated individual calculations,in which the critical slip surface tends to be determined without the optimized looking for or the iterative calculation.