考虑锚索腐蚀性能退化的边坡可靠度分析

Slope Reliability Analysis Considering Corrosion-induced Degradation of Cables' Performance

锚索因材料腐蚀引起性能退化对高边坡稳定具有重要的影响。为识别锚索腐蚀条件下的2种典型破坏模式,建立了相应的锚索锚固力时变模型。以锦屏一级左岸坝肩边坡代表性的Ⅱ_1-Ⅱ_1剖面为例,探讨了边坡开挖至1 780 m高程时3层抗剪洞和预应力锚索全部生效后3种工况下左岸坝肩边坡稳定性及可靠度的演化规律。结果表明:预应力锚索腐蚀作用对边坡稳定性及可靠度均具有重要的影响,锚索服役前期(120 a)边坡安全系数和失效概率变化相对较小,后期安全系数和失效概率变化幅度急剧增大,边坡稳定性条件迅速恶化。因此需要定期对处于腐蚀环境中在役预应力锚索等锚固结构进行合理的维护。此外,边坡可靠度分析有效地考虑了岩体及结构面力学参数变异性及互相关性对边坡稳定性的影响。

Degradation of pre-stressed cable＇ s performance caused by corrosion has significant effect on slope stabil- ity. In this research, two typical failure modes of pre-stressed cables in the presence of corrosion are identified, and the corresponding time-dependent anchored force models are established. The representative section Ⅱ1-Ⅱ1 of abut- ment slope at the left bank of Jinping I-stage Hydropower Station is taken as an example to illustrate the time-de- pendent slope stability and reliability of the slope excavated to elevation 1780 m and reinforced with three shear-resistant concrete plugs and pre-stressed cables under three conditions. Results indicate that the corrosion of pre- stressed cables has significant effect on both the stability and reliability of anchored slope. In the early stage （the first 120 years） of cable＇ s service life, the variations in the factor of safety and probability of slope failure are rela- tively small; whereas in the later stage, the variations increased sharply and the stability condition deteriorates rap- idly. Hence, reasonable periodical maintenance is required for the in-service anchored structures such as pre- stressed cables subject to corrosive underground environments. In addition, the influences of variabilities and cross- correlations of shear strength parameters of rock masses and structural planes on the slope stability can be effectively accounted for in the slope reliability analysis.