降雨是诱发边坡失稳的主要因素，为探明不同降雨强度条件下花岗岩残积土边坡的失稳模式，通过75、125、150、175 mm/h 4组不同降雨强度下边坡失稳现场试验，基于工程边坡原位监测试验采集的含水率-时间与位移-时间曲线研究了花岗岩残积土边坡渐进失稳破坏特征，并提出了降雨条件边坡失稳的持续时间与降雨量阈值。研究表明：降雨条件下花岗岩残积土边坡为渐进失效破坏，根据降雨强度斜坡失稳破坏可分为浅层局部滑动、浅层整体滑动与崩塌、深层局部滑动、深层整体滑动4种模式，斜坡发生变形失稳的区域主要位于坡脚位置，坡中次之，坡顶最小。边坡深层滑动从显著变形到失稳破坏历时18 ~ 20 min，而浅层滑动持续时间为25 ~ 135 min。土壤界限含水率可特征边坡失稳破坏过程，当斜坡土壤含水率上为42% ~45%时，斜坡开始出现开裂、蠕动变形等失稳征兆；当土壤含水率上升到47% ~ 50%时，坡面土体开始崩解并迅速发生滑坡、崩塌。

Rainfall is the main factor of slope instability. In order to study the evolution and migration law of slope humidity under rain infiltration under different rainfall intensities. The field tests of slope instability under different rainfall intensities of 75 mm/h, 125 mm/h, 150 mm/h and 175 mm/h were conducted, and the progressive failure characteristics of slope were studied according to the water-time-time and displacement-time curves, and the rainfall time and rainfall threshold of slope instability were proposed. According to the rainfall intensity, the slope instability failure can be divided into four modes: shallow local slide, shallow integral slide and collapse, deep local slide and deep integral slide. The deformation and instability of slopes are mainly located at the foot of the slope, followed by the middle of the slope, and the slope top is the smallest. It last 18 ~ 20 min for the deep slope to slide from significant deformation to instability, while the shallow slope to slide lasts 2 ~ 135 min. Slope instability and soil boundary water content can be significantly correlated with the failure process of slope instability. When the shallow soil water content of slope rises to 42% ~ 45%, the slope begins to show signs of instability such as cracking and creep deformation. When the soil moisture content rises to 47% ~50%, the soil on the slope begins to collapse and landslides and collapses quickly.