强降雨对库岸堆积体边坡稳定性影响的离心模型试验和数值模拟研究

Centrifugal modeling and numerical simulation on stability of reservoir bank accumulation slope caused by heavy rainfall

堆积体广泛分布于我国西南大江大河的河谷地带,在降雨条件下其稳定性直接关系到大坝的安全稳定。设计了水库库岸堆积体边坡强降雨离心模型试验系统,开展了强降雨诱发库岸堆积体边坡失稳离心模型试验,对降雨作用下滑坡地质演化及灾变过程进行研究。基于试验结果,进一步开展数值模拟研究,分析了满库容不同降雨强度下强降雨对不同库水位及堆积体渗透性的边坡稳定性影响。结果表明:水库蓄水阶段堆积体边坡前缘在浮托力和泡水软化作用下造成抗滑力下降。但指向坡体内的渗透压力对坡体起到加固作用。两种竞争机制作用下产生的后缘细微裂缝对降雨阶段边坡变形发展产生重要影响。降雨主要造成坡表侵蚀及径流,少部分从裂缝入渗造成后缘浅层下沉。若不加处理,则边坡有可能发生推移式整体破坏。因此,库岸堆积体边坡后缘裂缝的处置是地质灾害防治的关键。

The accumulation body is extensively distributed in the valley area of major rivers in southwest China,and its stability directly impacts the safety and stability of dams during rainfall conditions.To study the geological evolution and disaster processes of landslides during rainfall events,a centrifugal model test system is designed to simulate heavy rainfall on the slope of a reservoir bank,with a focus on investigating the induced instability of the accumulation body at full storage capacity.Following the test results,additional numerical simulation is carried out to analyze the influence of rainfall intensity,reservoir level state and permeability of accumulation body on slope stability.The results indicate that during the reservoir storage stage,the slope front of the accumulation body experiences reduced resistance to sliding due to buoyancy and water softening.However,osmotic pressure exerted on the slope body also contributes to its strengthening.The cracks formed at the rear edge as a result of these two competing mechanisms significantly influence the development of slope deformation during the rainfall stage.Rainfall primarily leads to surface erosion and runoff on the slope,with a small portion infiltrating through cracks,resulting in shallow subsidence of the rear margin.If the slope is left untreated,it is likely to experience overall failure.Therefore,addressing the cracks at the rear edge of the bank slope is crucial for preventing and controlling geological hazards.