降雨条件下折线型滑面的大型滑坡稳定性离心模型试验

Centrifugal model tests on large-scale landslide with broken-line slip surface under rainfall

以大型土工离心机为技术依托,采用离心模型试验,研究开挖和降雨对滑面为折线型的大型滑坡变形破坏和稳定性的影响。试验中采用变形标志点、颗粒图像测速技术(PIV)和可承受高离心力的传感器,在获取坡体土压力、孔隙水压力和位移矢量场的基础上,综合分析开挖和降雨诱发大型滑坡变形破坏的特征及失稳模式。试验结果表明,在滑面形态变化大的部位开挖卸荷容易引起折线型滑面大型滑坡的局部复活;受开挖卸荷和降雨影响,滑坡后缘的开挖斜坡位移最大且最先失稳;受降雨的影响,滑坡前部位移较大,坡体表面变形破坏严重,开挖斜坡下部发育一条次级滑裂面,滑坡后缘和开挖平台前沿滑面坡度突变处各形成一条潜在主滑裂面。离心模型试验显示折线型滑面的滑坡受开挖和降雨的影响可表现出分级分块滑动的变形破坏特征。稳定性分析表明,降雨使折线型滑面的大型滑坡不同滑段稳定性系数不同程度降低,滑坡后缘、开挖斜坡和滑坡前缘处于不稳定状态。

Based on the technical support of the large geotechnical centrifuge, centrifugal model tests are performed to study the effects of rainfall and excavation on the deformation and stability of large-scale landslide with broken-line slip surface. The marking points, the particle image velocimetry technology and the sensors which can withstand high centrifugal force are applied during the tests. The earth pressure, pore water pressure and displacement vector field are obtained to make a comprehensive analysis on the characteristics of deformation and failure and the instability modes of large-scale landslide induced by rainfall. The test results show：（1） The unloading by excavation in the slope with large change of slip shape is easy to cause the local landslide in large-scale landslide with broken-line slip;（2） Under the rainfall and excavation, failure in the excavation slope is the earliest, and it has the maximum displacement;（3） Affected by the rainfall, large displacement occurs at the toe of slope and serious failure occurs on surface. A secondary slip surface occurs under the excavation slope, and two main slip surfaces located on the head of the slope and the down edge of the excavation area with change of the angle of the slip surface. The centrifugal mode tests indicate that the characteristics of deformation and failures of large-scale landslide with broken-line slip surface exhibit slide in different grades and blocks under the influence of excavation and rainfall. The stability analysis shows that the rainfall reduces the factor of safety of large-scale landslide, and the head of slope, excavation slope and slope toe are instable.