基于强度折减概念的滑坡稳定性三维分析方法(Ⅱ):加固安全系数计算

结合乌江洪家渡1#塌滑体加固设计工程,探讨了滑动面已知的条件下滑坡稳定性的三维分析方法。首先,模拟了塌滑体在天然状态下处于极限平衡状态时的滑动方向,并使用其应力成果计算了塌滑体的三维安全系数;其次,建议了基于强度折减概念的三维加固安全系数计算方法:最后,提出了加固设计的进一步优化方案。计算结果表明,塌滑体的滑动方向与局部地形等高线近于垂直。主滑方向变化较大,自后缘的NE15°方向逐步过渡到中部的NS向,最终过渡到前缘的NE30°方向,以致很难作出能表征主滑方向的地质剖面。基于应力计算成果的安全系数计算公式不能充分考虑滑坡体的抗滑潜能,也不能充分反映滑坡体的滑动方向,安全系数偏大。基于强度折减概念的三维加固安全系数计算方法具有有限元等方法的优点,较好地克服了上述局限性,可以合理地评价加固后的滑坡稳定性。

3D stability analysis of landslides based on strength reduction (Ⅱ):evaluation of reinforcing factor of safety

Taking the No. 1 landslide at Hongjiadu Hydroelectric Project for example, a 3D stability analysis method is discussed for landslides with known slip surface. Firstly simulation is made for its sliding directions and calculation is completed for its three-dimensional factor of safety by a stress-based method, assuming the landslide is in critical state under natural conditions; secondly a method is proposed for its 3D evaluation of reinforcing factor of safety, which is based on the strength reduction technique; and finally measures are proposed for further optimizing the reinforcing design. Results show that sliding directions are nearly perpendicular to the local contour lines; the major sliding direction changes drastically from NE15?in the rear to NS in the middle, and finally to NE30?in the tongue, making it difficult to draw a longitudinal geological profile, which can represent the major sliding directions. The stress-based method can neither fully utilize the anti-sliding potentials of the slide, nor represent its overall sliding directions, leading to over-estimation of its factor of safety. The proposed method, having the merits of finite element method, etc., can overcome the above drawbacks and rationally evaluate its reinforcing factor of safety.