库水位升降条件下边坡失稳离心模型试验研究

CENTRIFUGAL TEST ON SLOPE INSTABILITY INFLUENCED BY RISE AND FALL OF RESERVOIR WATER LEVEL

三峡库区频发的滑坡地质灾害已愈来愈引起学者的高度重视,其受水位反复升降的影响是库区边坡不同于其他陆地自然边坡的一个显著特点。以离心模型试验为手段,基于三峡库区典型滑坡的工程地质特征,建立相应的土质边坡离心模型。在试验过程中实现对库水位循环升降的控制,模拟库区边坡在水位升降作用下的失稳过程。通过数码摄像、数字图像处理和传感元件测试,获得该试验条件下的土坡在水位升降过程中典型位置的孔隙水压力变化、全断面位移矢量演化(水平位移和沉降)、滑面形态及裂缝形成发展过程,并详细分析边坡在这种外部水环境影响下的变形演化、失稳和破坏模式。试验结果表明,若仅考虑水位升降作用的影响,该试验条件下的库区土质边坡的变形呈现典型的渐进牵引破坏模式,并具备较强的水土软化影响特征;裂缝在变形演化过程中出现交替张开和闭合现象,该失稳模式下的滑面呈折线形态,并在变形破坏过程中次生多级滑面。研究结果为库区滑坡地质灾害机制的深入认识、以及滑坡预防和控制提供了重要依据。

Many scholars have paid more and more attention to the landslide disasters occurring in the Three Gorges Reservoir region. It is a special characteristic that the slopes along reservoir are inevitably influenced by rise and fall of water level. A method to evaluate the slope stability by centrifugal test is introduced; and soil slope models considering geological conditions of the Three Gorges are constructed. Controlling of drawdown and charging of reservoir is implemented in the test, which makes it possible to simulate the whole process of instability of the slopes. Through the technioue of digital photography, image processing and transducers measurement, a series of important test data are obtained, such as pore water pressure, displacement, failure surface and crack evolution in some typical regions. Moreover, analysis of deformation progress and failure mode are given as well. Results indicate that the deformation of soil slopes will perform pull-typed behavior in such water condition. However, the factor of water rise and drawdown gradually softening soil will lead to the strength reduction and therein induce large displacement. In addition, the slope cracks propagate and close alternately during the whole test; and failure surfaces are almost like polygonal lines. The centrifugal results can provide significant data for evaluating the failure mechanism of such landslides, which will provide useful information for the prevention and reinforcement measures in reservoir landslides.