三峡库区黄南背西危岩体变形机理研究及失稳模式预测

Study on deformation and failure mechanism of Huangnanbeixi dangerous rock in Three Gorges Reservoir Area

自三峡库区2009年蓄水至175 m以来,库水位常年在高程145-175 m间波动,形成了高差30 m的水位变动带(消落带)。由于该变动带上岩体长期在饱和浸泡-风干曝晒的循环作用下,其物理力学强度不断减弱,于是大量的新生危岩和滑坡塌岸相继形成,此类地质灾害不仅点多面广,且破坏频率高,诱发因素甚多。本文以黄南背西危岩体为典型案例,基于影像资料、原位测试数据以及离散元数值模型深入分析了该危岩体未来失稳的破坏模式和变形成因机理,重点对该危岩体的应力场、形变场和基座岩体受水位作用影响展开研究。研究表明黄南背西危岩体发生失稳破坏的三种因素:1)底部岩体出现压溃破坏,2)底部破碎岩体受水影响劣化加剧,3)基座角砾岩岩体遇水水解。危岩体发生破坏将从其底部岩体出现压溃开始,上部岩体随后下错滑移,失稳岩体发生倾倒、滑移和坠落的复合型破坏。

After the 175 m impoundment in the Three Gorges Reservoir Region, the reservoir water level fluctuates between the elevation of 145-175m periodically, forming a water level variation belt with a height difference of 30m. As the physical and mechanical strength of the rock mass in this belt is gradually weakened with the frequency of saturated soaking and drying, a large number of newborn rockfalls and landslides have been formed. These geological disasters are widespread, have high frequency of destruction and too many inducing factors. This paper takes the Huangnanbeixi reservoir bank as a typical case. Based on the image data, in situ test data and the establishment of the discrete element numerical model (UDEC), the formation mechanism and failure mode of the future instability failure of the critical rock are analyzed in detailed. The effect of the position was studied. It is found that the unstable rock mass of Huangnanbeixi is coupled by three factors, included stress concentration of Marginal rock mass , base deterioration and underlap breccia dissolution. Its failure will start from the cave lower rockmass, then overlying rock mass falls, finally, the collapse, slip and falling damage of the rock mass are combined.