水位骤变条件下河流崩岸模型试验及机理研究

为研究水位骤变条件下河流崩岸的形成机理,结合现场调研及室内模型试验,分析了水位骤变条件下河流崩岸过程及孔隙水压力的变化规律。结果表明,在水位上升过程中,水土结合部位易产生裂缝,并不断拓展形成贯穿性裂缝,影响岸坡结构完整性,同时局部区域产生坍塌现象形成临空面,为后续坡体大规模坍塌提供条件;水位骤降后,由于水体惯性牵引,坡脚掏空,失去支撑,坡体发生整体下滑(由试验前的45°坍塌成31°),产生条崩现象;在库区水位骤降时,坡体内孔隙水压的消散速度低于坡前水位骤降速度,土体内外形成较大的水压力梯度(孔隙水压力),进而诱发大规模崩岸。揭示的河流崩岸内在机制,对于库岸安全管理具有较大的参考价值与实际意义。

Model Test and Mechanism Study of River Bank Collapse at Sudden Change of Water Level

This paper analyzes the process of river bank collapse and the change law of pore water pressure under the condition of sudden change of water level based on field investigation and laboratory model test in order to study the formation mechanism of river bank collapse.The results show that the cracks are easy to be appeared at the joint of water and soil in the process of water level rising,and they are constantly expanding to form penetrating cracks,which affect the structural integrity of the bank slope.The collapse phenomenon occurs and it forms the air-facing surface in local area,which provides the condition for the follow-up large-scale bank collapse.After the water level drops suddenly,the slope body loses its support,and the whole slope falls down because of the inertia traction of the water body and the hollowed toe(from 45°before the experiment to 31°after the experiment),resulting in strip collapse.When the water level drops suddenly in reservoir area,the dissipation velocity of pore water pressure in the wave body is lower than that in front of the slope,and a large gradient of water pressure(pore water pressure)is formed inside and outside the soil,inducing large-scale bank collapse.The revealed intrinsic mechanism of river bank collapse has the great reference value and practical significance for the safety management of river and bank.