降雨诱发浅层黄土泥流的形成机制及强度研究

The shallow loess mudflow induced by rainfall has been identified with extensive development and high frequency occurrence as a disaster though it is of small dimension. Merely in the flood season of 2012, 7 deaths have been caused in Baoji, Shaanxi province, which urges the development of research on its failure mechanism and intensity. Based on the investigation of typical cases, the following research plans are drawn:.•Conduct form mapping on types of mudflow such as the flaying erosion type, slumping type and washout type with 3D laser scanning radar, quantitative description of the volume expansion features of mudflow, and finally establish the initiation and flow modes of shallow loess mudflow; .•Analyze the material composition and structure differences between the mudflow and original loess, and conduct mechanical deformation test for unsaturated humidifying of loess;.•Monitor the rainfall infiltration process in the single-side slopes with a slope angle of 0-60º and slopes gentle on slope shoulder, with an aim to study the controlling features of the slope forms on rainwater convergence, infiltration and matric suction variation, and reveal the water and soil responding mechanism during the mudflow fluid motion process; .•Analyze the physical mechanics model, and discuss the flow energy transformation features of mudflow, aiming to establish the strength calculation model of rainfall induced mudflow disaster, and provide theoretical supports for the quantitative calculation of rainfall induced disaster. .The research results would contribute greatly to the studies on the mechanism of water and soil coupling in the loess slop induced by rainfall, and provide new thought for the monitoring and early warning of mudflow disaster in Loess Plateau area, which is of both scientific and social significances..

降雨诱发的浅层黄土泥流规模小、发育范围广、致灾频率高，仅2012年汛期，在陕西宝鸡地区就造成7人死亡，急需开展其形成机制与强度的研究。本项申请拟以典型案例调查为基础，利用三维激光扫描雷达对剥皮侵蚀型、冲蚀型泥流及滑塌型泥流等类型进行形态测绘，定量描述泥流体积扩容特征，建立浅层黄土泥流启动与流动模式；分析泥流与原状黄土物质成分、组成结构差异，开展黄土非饱和增湿力学变形试验，监测0-60 º单面坡与坡肩平缓斜坡的降雨入渗过程，研究坡体形态对雨水汇聚、入渗及基质吸力变化的控制性特征，揭示泥流流体运动过程中水土响应机制；对物理力学模型解析，讨论泥流流动能量转化特征，建立降雨诱发泥流灾害的强度计算模型，为降雨泥流灾害危险性定量计算提供理论支撑。研究成果将把降雨诱发黄土斜坡失稳中的水土耦合的机制研究推向一个新台阶，为黄土高原地区泥流灾害监测预警提供新思路，具有一定的科学与社会意义。

为分析黄土泥流的形成机制与活动强度，项目以陕西宝鸡地区与甘肃天水地区的6处典型的黄土泥流灾害的调查为基础，先后开展了2处现场入渗水文过程观测试验，马兰黄土与古土壤低应力增湿变形试验15组，体积为2立方米的降雨入渗模型试验6组，数值模拟试验3组。系统对比分析了宝鸡地区粘黄土、天水地区砂黄土的力学性质差异、坡体形态对降雨入渗-积水的响应、黄土斜坡对降水入渗的力学响应机制、富水黄土粘滞性流动性。研究表明：黄土的物质组成与结构是泥流产生的基础，特别是其大孔隙、弱胶结结构。黄土泥流是一个渐进的过程，干湿循环作用产生的裂隙、孔隙的扩展是触发泥流渐进爆发的关键。黄土斜坡的坡型会影响泥流的产生，坡体越陡峭，坡面爆发泥流的可能性越低。斜坡体的汇水区域是泥流发育的关键位置，泥流多自饱和区开始渐进扩展滑动，其的活动强度与饱和区域的范围的大小有关。超孔隙水压力出现受泥流体积的压缩控制，泥流的运动速度远近与超孔隙水压力大小有关。总结上述研究成果，项目发表5篇论文，4篇第一资助，包括2篇SCI/EI论文。