地震作用下预应力锚索边坡的稳定性分析

Stability analysis of prestressed anchor cable slope under seismic loads

稳定性分析对边坡工程具有重要的意义。为探究地震对预应力锚固边坡的影响,基于预应力锚索具有安全储备的特点,分析了地震作用下边坡的分阶段模型。在传统Newmark法的基础上,采用拟动力计算,推导了顺层岩质边坡的位移、锚固力和安全系数计算公式。结合工程两个算例,探究了不同锚索模型和地震累积作用下的边坡变形规律。由结果可知,当锚索锚固力取固定值时,边坡计算位移偏大,随时间呈线性增长。当考虑锚索的安全储备时,位移增长速率随时间逐渐减小,最后趋近于定值。不同锚索模型对位移影响较大,锚索储备作用不可忽略。同时地震会对预应力锚固边坡产生永久性影响。当再次发生扰动时,其表现为临界滑动阈值的提升,位移增长率与受震经历的加速度幅值呈反指数变化。以露天矿区边坡为背景,在抗震设防标准下确定最佳支护方案。

Stability analysis is of great significance to the safety of slope engineering.In order to study the influence of seismic loads on slopes strengthened by prestressed anchor cables,firstly,the staged model of slope stability under seismic loads is analyzed based on the safety reserve characteristics of prestressed anchor cable,and secondly,the formulas of displacement,anchoring force and safety factor of bedding rock slope are derived by using the traditional Newmark’s displacement calculation method.At last,two examples are used to study the displacement behavior of prestressed slope under different cable models and seismic accumulations.It can be seen from the results that when the anchoring force is taken as a constant value,the calculated seismic slope displacement is larger and increases linearly with time.When considering the safety reserves of anchor cables,the growth rate of displacement gradually decreases with time and finally reaches a constant value.Different cable models have great influence on the calculated displacement,and the reserve effect of cable cannot be ignored.Seismic loads,meanwhile,have a permanent effect on the prestressed anchor slope.The critical threshold of slope sliding increases if the slope is re-disturbed seismically.Displacement growth rate is inversely exponential with the acceleration intensity of the last shaking.Finally,taking the slope of an open pit mining area as a case study,the optimum supporting scheme is determined under the seismic fortification standard.