降雨诱发粉土边坡失稳的离心模型试验及雨强-历时警戒曲线的验证

中国东南沿海山地丘陵地区气候湿润,每年梅雨季和台风侵袭时都伴随有大量土质滑坡,研究降雨诱发土质滑坡的失稳模式和机理对该类滑坡预警预报及防治具有重要意义。笔者自行研制了离心机机载降雨模拟装置,在50g条件下模拟和再现了非饱和粉土边坡在不同强度降雨条件下的失稳破坏过程,揭示了降雨诱发粉土边坡的失稳模式为坡脚局部失稳—向上扩展—整体浅层滑动,滑动面深度介于1~3 m。3组试验获得了降雨强度与边坡失稳时降雨历时关系数据,与李鹤等针对东南沿海地区残积土边坡提出的雨强-历时警戒曲线（I-D曲线）最为接近,验证了该降雨量警戒曲线的有效性。对离心模型试验结果进行反分析表明：非饱和土渗流分析能有效模拟边坡降雨入渗过程,而现有极限平衡分析方法难以准确捕捉降雨诱发边坡由局部向整体发展的失稳过程。基于所揭示的失稳模式,指出了该类降雨诱发滑坡的有效防治措施主要包括坡脚加强排水和支护、坡面防渗和防护。

Centrifuge modelling of rainfall-induced slope failure in silty soils and validation of intensity-duration curves

As the southeastern coastal area in China has a humid climate,lots of landslides in soil slopes are induced by rainfall during the rainy season and typhoons every year. It is of great importance to investigate the failure modes and mechanism of rainfall-induced slope instability. A rainfall simulator installed on the centrifuge model box is developed, and the failure process of the silty slope subjected to different rainfall intensities is reproduced. The observed failure mode startes from local failure at the slope toe, extends upward and finishes with a global shallow landslide. The depth of the slip surface is 1 to 3 m. It is found that the data points of relationship between rainfall intensity and rainfall duration from the three centrifugal model tests are close to the intensity-duration curve proposed by Li et al. (2012) for the early warning of landslides in a residual soil slope in the southeastern coastal area of China. The back analyses of the experimental results indicate that unsaturated seepage analysis is able to simulate the rainfall infiltration processes into the slope, but it is difficult for the existing limit equilibrium methods to capture the local to global failure process induced by rainfall accurately. Based on the observed failure modes, the mitigation measures for this kind of rainfall-induced instability mainly include draining and retaining at the toe of slopes as well as reducing infiltration on the slope surface.