Highlights:

（1）边坡变形的多源数据监测；

（2）水库边坡变形特征及分区；

（3）降雨和库水位变化对边坡变形破坏机制的影响。

Cover Story

Reservoir water level fluctuation, rainfall and their combined influence easily cause the deformation and failure of reservoir slope, and have caused some catastrophic events such as the 1963 Vajont landslide in Italy, 1959 Malpasset arch dam failure in France, and the 2003 Qianjiangping landslide in the Three Gorges Reservoir of China. During the reservoir impoundment period, changes in physical and mechanical parameters of the slope materials and in hydraulic environment significantly affect the stability of the slope. The potential unstable slope not only threats the safety of the hydropower station and reservoir but also infrastructures. Thus, understanding the failure mechanism of this kind of slope in the reservoir area is the key to providing advice for potential unstable slope design reinforcements. Nevertheless, a big challenge for revealing the deformation and failure mechanism of the reservoir slope is the unavailability of long-term deformation and displacement monitoring in the slope or on the slope surface. The Xiluodu hydropower station on the Jinsha River, southwest of China has a water level fluctuation between the elevations of 540 m and 600 m each year with a capacity impoundment of up to 12.8 billion m³. Valuable information reveals that more than 80 landslides and collapses are distributed in the Xiluodu reservoir. The reservoir slope prevention and mitigation is a major challenge during hydropower station construction and operation.

To investigate the deformation mechanism of Yanjiao rock slope in the Xiluodu reservior, we conducted comprehensive field investigation, geotechnical reconnaissance, slope surface GPS monitoring, and inclinometer deformation monitoring in the slope. The photograph on the cover in Journal of Mountain Science (Vol. 20, No. 1, 2023) illustrates the overall Yanjiao rock slope on the left bank of the Jinsha River. The distribution of cracks in the slope reveals that the Yanjiao slope can be divided into a bank collapse area and a strong deformation area. The rear area of the slope has been experiencing persistent deformation with a maximum cumulative displacement of 505 mm and 399 mm in the horizontal and vertical directions, respectively. The potential failure surface of the slope is formed 36 m below the surface based on the borehole inclinometer data. The bank collapses of the Yanjiao slope are directly caused by the reservoir impoundment while the deformation area of the slope is affected by the combination of the rainfall and reservoir water level fluctuation. Based on failure mechanism of the slope, the surface drainage, slope unloading, and prestressed anchor are recommended to prevent potential deformation.

封面故事

随着大量的高坝水库的建成运行，水库边坡变形或滑坡将对水利枢纽系统的安全运行和库岸人民生命财产带来巨大的安全隐患。1963年意大利瓦依昂水库滑坡造成2000多人丧生, 2003年三峡库区的千将坪滑坡导致24人死亡。水库边坡是极其复杂的大型地质体，其受内外动力耦合作用，而库区水位变动和降雨是其变形失稳的关键影响因素。水库水位变动不仅会直接影响边坡前缘岩土体的物理力学性质，而且会显著改变边坡的水文地质环境和水动力环境，从而影响边坡的稳定性。此外，降雨的入渗作用也将直接影响水库边坡变形及其稳定性，降雨与水位变动的联合作用会形成叠加效应，导致边坡变形渐进累积。弄清水库边坡变形失稳机制是边坡加固设计的关键，也是水库边坡防灾减灾的基础。然而，揭示水库边坡变形失稳机制的一大挑战是缺乏长期的边坡多源观测及监测数据。

溪洛渡水电站是国家“西电东送”骨干工程，位于四川和云南交界的金沙江上，于2014年建成运行，总蓄水量为128亿方，库水位在540～600 m之间周期性升降。在水电站运行期间，距离电站大坝上游75km的左岸岩脚边坡产生变形，严重威胁岩脚集镇部分居民房屋和公路交通要道的安全。基于此，本期（2023年20卷第1期）封面文章作者对岩脚边坡进行了详细的现场调查, 岩土钻探, GPS位移监测以及钻孔倾斜测量。封面图片展示了岩脚边坡整体形态和所处地质环境。根据边坡坡表裂缝分布特征，将岩脚边坡变形区划分为库岸塌岸区和强变形区；GPS数据揭示边坡后缘产生了持续的变形，水平向和竖直向累积位移分别达到505mm和399mm；钻孔倾斜数据揭示岩脚变形边坡的潜在滑动面位于地表36m以下。结合库水位变动、降雨等数据和边坡变形速率之间的关系，发现岩脚边坡库岸塌岸区直接受库水位变动的影响，而强变形区受库水位变动和降雨的共同作用。基于此，建议采用坡面排水、卸载以及预应力锚索的综合措施加固该边坡。

目前，学术界和工程界对水库边坡已开展了大量研究，积累了丰富的经验，并服务于重大工程实践。但多因素作用下水库边坡的变形失稳机制涉及多学科交叉融合，极其复杂，亟待更多的深入研究。

Citation: Wang NF, He JX, Du XX, et al. (2023) Deformation and failure mechanism of Yanjiao rock slope influenced by rainfall and water level fluctuation of the Xiluodu hydropower station reservoir. Journal of Mountain Science 20(1). https://doi.org/10.1007s11629-022-7755-0

Downloads: https://doi.org/10.1007s11629-022-7755-0

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