粘性泥石流侧蚀作用机制及计算模型研究

Viscous debris flow bank erosion often causes a large amount of loose material to enter the channel on the gully, which increases the scale of the hazards and causes secondary hazards such as collapse and landslide. Therefore, bank erosion has an important influence on the evolution process of the viscous debris flow. Previous research focused on the bed erosion, less on the bank erosion, and more on the river bank erosion method to calculate the bank erosion rate of the debris flow. Because the physical properties of the viscous debris flow are complex, and the interaction mechanism between the viscous debris flow and the gully bank is significantly different from that of the bed, so that it is difficult to accurately calculate the bank erosion rate of the viscous debris flow. This project intends to carry out research on the mechanism of viscous debris flow bank erosion and the calculation of bank erosion rate through field investigation, indoor tank experiment and theoretical analysis. Based on the boundary layer theory and river dynamics theory, the lateral motion response mechanism of viscous debris flow under the action of bank sidewall is proved. The bank sidewall resistance characteristics of the viscous debris flow under different motion characteristics are analyzed, and the quantitative model of viscous debris flow bank sidewall resistance is constructed. The analysis analyzes the mechanical mechanism and response of the viscous debris flow bank erosion process, and finally establishes the calculation method of the viscous debris flow bank erosion rate, and verifies it by field in situ experiment and field-observation. This study can provide a theoretical basis for the evolution mechanism and engineering prevention of viscous debris flow.

粘性泥石流侧蚀常造成沟岸大量松散物质进入沟道，使灾害规模增大，同时引发崩塌滑坡等次生灾害，因而侧蚀对粘性泥石流演进过程有重要影响。既往的研究侧重底蚀，较少关注侧蚀，多借鉴河岸侧蚀方法进行泥石流侧蚀率计算。由于粘性泥石流物理性质复杂，且粘性泥石流与侧壁相互作用机理相比于和底床相互作用机理差异明显，以致难以准确计算粘性泥石流侧壁侵蚀率。本项目拟通过野外调查、室内水槽实验、理论分析等手段，开展粘性泥石流侧蚀作用机制及侧蚀率计算模型研究。基于边界层理论及河流动力学理论，探明侧壁作用下粘性泥石流的侧部运动响应机制；分析不同运动特征下粘性泥石流侧部阻力特性，构建粘性泥石流侧壁阻力定量化模型；通过量纲分析阐明粘性泥石流侧蚀过程的力学机制及响应，最终建立粘性泥石流侧蚀率的计算方法，并通过野外原位实验及原型观测进行验证。该研究可为粘性泥石流的演进机制和工程防治提供理论依据。

本项目以粘性泥石流为研究对象，围绕泥石流表面运动特征及响应机制、泥石流与侧壁相互作用机制及动力学关系、泥石流侧蚀机制及侧蚀过程分析等研究内容，通过野外调查、文献调研、室内试验、理论分析等开展研究，圆满地完成了任务书要求的工作，取得成果如下：（1）通过野外调查和文献调研，获取了野外泥石流性质、泥石流侧壁状态参数和沟床特性；确定了雷诺数等无量纲参数范围，并基于此设计了室内水槽实验方案。（2）通过室内物理实验，分析了不同影响因子条件下泥石流的流速分布特征；将流速值趋于稳定和接近的区域划定为主流区，将侧壁与主流区之间的区域划定为侧壁影响区域。（3）基于水槽实验测量数据，将侧壁影响区域范围进行归一化，建立一个新的无量纲参数为侧壁影响距离d与侧壁代表粒径d84的比值，并验证了其可靠性。（4）根据实验获取的流速分布曲线，计算得到流速分布曲线的剪切速率，进一步结合流变模型，获取对应的侧壁切应力，实现粘性泥石流侧壁阻力的定量化分析。（5）从整体堆积体被侧部侵蚀的控制因素来看，整个侧蚀过程可以划分两个阶段。分别是坡脚冲刷阶段和坡顶崩滑阶段。坡脚冲刷阶段的主控因素是水力侵蚀，坡顶崩滑阶段的主控因素是重力侵蚀。研究成果为泥石流的演进机制和工程防治提供理论支撑。已发表论文7篇，其中SCI论文6篇，CSCD论文1篇；获授权发明专利2项；以本研究为基础，项目负责人获批国家自然科学基金面上项目1项。