加筋土坡动态稳定性拟静力分析

DYNAMIC STABILITY PSEUDO-STATIC ANALYSIS OF REINFORCEMENT SOIL SLOPES

加筋土工结构被广泛采用的原因不仅是其具有良好的静力性能,且也在于出色的动力稳定性能,现有研究较少考虑竖向地震效应对加筋土坡动态稳定性的影响。基于塑性极限分析上限理论,假定不同的破坏面,同时考虑水平和竖向地震影响并结合不同加筋模式,采用拟静力分析方法推导一定加筋强度条件下的边坡临界高度和一定边坡高度条件下的临界加筋强度计算公式,并对所导公式采用序列二次规划法进行了优化计算,数值计算与分析表明:简单静态和动态条件下,该结果与现有研究成果有较好的一致性,可以证明该方法的正确性;水平和竖向地震、岩土材料强度特性、边坡倾斜度均对加筋土坡的动态稳定性有重要影响,特别当边坡较陡,岩土填筑材料质量较差和地震影响强度较大时,忽视竖向地震影响将会导致设计偏于不安全;最后针对工程实际,提出相应的工程建议。

The reinforced soil structures are employed widely due to the technical and economical advantages in static state. In addition, the use of reinforced soil structures in seismic areas has been increased due to their excellent seismic stability, but the vertical seismic effects on the stability of reinforced soil structures are seldom considered. The effects of horizontal and vertical pseudo-static forces on reinforcement soil slopes are investigated by applying the kinematical approach of limit analysis theory. In particular, the effects of the distribution mode of the reinforcement force on the seismic stability of reinforced soil slopes have been investigated as well. Both rotational failure surface and planar slip surface are considered and each analytical expressions is derived to calculate the reinforcement force, which are required to prevent failure and the critical height of reinforced slopes subjected to earthquake loading. The upper bound solutions for each analytical expression are presented by applying a nonlinear sequential quadratic programming algorithm. From the contrastive analysis, it is shown that the solutions presented here agree well with available predictions both in simple static state and dynamic state. All of the seismic force, the material characteristic of soil and the gradient of slope have significant effects on the seismic stability of reinforcement slope. The effect of vertical seismic acceleration on the stability of reinforcement slopes is significant, especially for steep slope, poor quality filler and high value of horizontal seismic acceleration, which means that ignoring the effect of the vertical seismic acceleration could result in an unsafe design. Besides, some suggestions for engineering practice are proposed.