近坝边坡的稳定性对大坝和水电站运行安全至关重要, 锦屏一级水电站投入运行近10年, 左岸近坝边坡部分区域变形仍未收敛, 其变形机理尚未完全明确。锦屏左岸的深部裂缝对水电站设计期拱坝轴线选择影响较大, 而研究深部裂缝成因及对边坡变形的影响对边坡和拱坝安全具有重要意义。该文通过数值模拟分析锦屏河谷演化过程中地应力的变化特征, 研究深部裂缝形成的影响因素和力学机制。研究结果表明： 深部裂缝的形成与河谷下切、 左岸边坡复杂地质条件、 构造应力密切相关。受上述因素影响, 高高程岩体向深部卸荷, 在河谷下切后期发生应变能快速释放现象, 造成深部岩体发生卸荷破坏形成深部裂缝; 低高程岩体虽仅在表层发生卸荷破坏, 但随深度增加, 主压应力σ1与主拉应力σ3比值减小, 且主压应力σ1保持较高量值, 使深部岩体发生压剪破坏形成深部裂缝。该文通过分析边坡变形监测资料和河谷演化蠕变计算, 研究了深部裂缝与边坡运行期持续变形之间的关系。分析监测资料表明： 煌斑岩脉和断层等软弱带是产生边坡运行期变形的主要因素, 深部裂缝和构造应力对边坡变形的影响较小。
Abstract
[Objective] There have been numerous cases of dam failures caused by slope instability in water conservancy projects domestically and internationally, leading to significant casualties and property losses. Therefore, the stability of the slopes near the river banks is crucial for the operational safety of dams and hydropower stations. The Jinping Dam, features a massive engineering slope on its left bank. For approximately 10 years following the commencement of operations at the Jinping I Hydropower Station, certain areas near the dam on the left bank have exhibited persistent deformation, and the underlying mechanisms are still not fully understood. The presence of deep cracks on the left bank significantly influences the selection of the arch dam axis during the design phase. [Methods] This paper utilizes numerical simulation to analyze the variation characteristics of in-situ stress during the evolution of the river valley, aiming to clarify the influencing factors and mechanical mechanisms behind the formation of deep fractures. Additionally, by leveraging monitoring data on slope deformation and conducting a creep analysis of river valley evolution, this paper examines the relationship between deep fractures and the continuous deformation of the slope during operation. [Results] This study found that the formation of deep fractures was closely related to valley incision, the complex geological conditions, and the tectonic stress of the valley slope. Owing to these factors, the unloading depth gradually decreased with a decrease in elevation. Consequently, when the rock mass at higher elevations experienced unloading at greater depths, the rapid release of strain energy occurred during the later stages of valley incision, which led to the unloading failure of the deep rock mass and the formation of deep fractures. Moreover, although the rock mass at lower elevations only experienced surface unloading failure, as the depth increased, the ratios of principal compressive stress and principal tensile stress decreased and the former remained at a high value. This resulted in compressive shear failure and the formation of deep fractures in the deep rock mass. Monitoring data showed that the arch thrust of the dam body hindered deformation in the empty direction, and displacement at high elevations was mainly due to gravity-driven tipping deformation. A comparison of apparent and deep deformation revealed that lamprophyre dikes, faults, and other weak zones were the main factors affecting slope deformation during operation, while the influence of deep fractures was not significant. Additionally, the tectonic stress of the mountain on the left bank had minimal impact on slope deformation. The results of the creep calculations were consistent with the observed deformation patterns of the slope during operation, further confirming that the influence of tectonic stress on slope deformation had dissipated. [Conclusions] In summary, this paper identifies the causes and mechanical mechanisms of deep fractures through finite element calculations and analysis of measured monitoring data, enhancing the engineering understanding of such slope issues. Compared with weak zones such as faults, deep fractures have less influence on the long-term deformation of the slope. The influence of tectonic stress on slope deformation has dissipated, which provides a foundation for further studies on the left bank slope of Jinping I Hydropower Station.
关键词
锦屏一级 /
岩质边坡 /
深部裂缝 /
河谷演化 /
蠕变
Key words
Jinping I /
rock slope /
deep fractures /
evolution of river valley /
creep
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基金
国家自然科学基金项目(41961134032)
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