薄层水流冲刷条件下斜坡土体的临界起动

Critical incipient motion of slope soil under thin layer flow scouring

斜坡土体侵蚀是丘陵地区和水库岸坡普遍存在的灾害现象,其主要动力因素是降雨或者波浪上爬产生的薄层水流对土体产生的冲刷剪切作用。为探索水流冲刷作用下的斜坡土体临界起动条件,采用自主研发的冲刷起动试验装置,开展斜坡土体的冲刷起动试验和理论研究。通过颗粒染色和高倍数电子显微等技术手段观测无黏性土颗粒的起动现象,确定了无黏性岸坡土体的起动模式与水流流速的相互关系;探索了不同干密度、不同黏粒含量及不同坡度与黏土斜坡临界起动流速的相互关系,土体的黏粒含量、干密度及坡度对黏性土体的起动流速影响较大,与干密度和土体坡度相比,黏粒含量对黏土斜坡的起动流速影响更为明显。验证了无黏性岸坡土体的临界起动方程,其中滚动起动流速方程具有较强的可靠性;基于黏土的起动模式构建了黏土斜坡的起动力学平衡方程,获得了黏土斜坡半经验半理论的起动流速方程,用试验结果求解了起动流速方程的相关参数,最终确定的起动流速公式与试验结果拟合度较好,同时验证了起动流速公式的可靠性。

Slope soil erosion is common in hilly regions and reservoir bank slopes,as the primary driving force is brought by the thin overland water flow caused by rainfall or wave run-up,which results in the shear force and subsequently the incipient motion of soil.In order to explore the incipient motion conditions of slope soil under waterflow scouring,the incipient motion test and theoretical research of slope soil were carried out via selfdeveloped testing device.The incipient motion phenomenon of cohesionless soil particles was observed by particle staining and high magnification electron microscopy,and the relationship between incipient motion mode of cohesionless bank slope soil and flow velocity was determined.This study also explored the relationships among differing dry densities,clay contents,and slopes with the critical incipient motion velocity on a clay slope,the results showed that clay content,dry density,and soil gradient had a great impact on the incipient velocity.Compared with the dry density and gradient,clay content had a clearer impact on incipient velocity.The incipient motion velocity equation of cohesionless bank slope soil was verified,and the rolling incipient motion velocity equation was reliable.The incipient motion mode of clay was used to establish the mechanical balance equation of the clay slope.Then,a semi-empirical incipient motion velocity equation of the clay slope was deduced,of which the relevant parameters were solved using the test results.The proposed incipient motion velocity equation showed good fit with the test results,and the verification results demonstrate that the equation is reliable.