泥石流拦砂坝底扬压力分布及影响因素试验

Experiment on distribution and influence factors of uplift pressure acting on bottom of debris flow check dam

泥石流拦砂坝底的扬压力会抵消坝体的部分有效荷重,影响其抗倾覆稳定性。为了研究拦砂坝底扬压力的分布规律及其影响因素,设计制作了拦砂坝模型和扬压力采集系统,开展了不同沟床坡度和不同坝前堆积条件下的扬压力模拟试验。试验结果表明,扬压力自坝踵至坝趾不断减小,且与渗流距离呈线性关系,当坝前有堆积物时相关系数绝对值达到0.98以上;沟床坡度明显影响坝底扬压力的分布。随着沟床坡度的增加,扬压力不断减小,且对坝踵处扬压力的影响较坝趾处更大;坝底和坝前堆积物的渗透性对扬压力的影响也很显著,它们的渗透性越差,扬压力就越小;坝前堆积物的渗透性还显著影响扬压力的分布规律,渗透性越差,其分布规律性就越强。研究成果为深入研究泥石流拦砂坝底扬压力的作用过程和作用机制奠定了基础。

The uplift pressure acting on a bottom of debris flow check dam can counteract partial effective weight and reduce the overturning stability of the dam. To study the distribution laws and influence factors of uplift pressure, a check dam model and an acquisition system of uplift pressure were designed and produced. A series of simulation tests of uplift pressure was conducted based on different gully bed slopes and different accumulations in front of the dam heel. The experimental results show that the uplift pressure linearly decreases from dam heel to dam toe. When placing accumulations in front of the dam, the absolute values of correlation coefficients between the uplift pressure and the distance to dam heel exceed 0.98. The uplift pressure decreases with the increase of gully bed slope and the influence of the bed slop on the pressure at the dam heel is greater than that of the dam toe. The permeabilities of materials placed on gully bed and accumulations in front of the dam all have impacts on uplift pressure. The lower their permeabilities are, the lower the uplift pressure will be. The permeability of accumulation in front of the dam heel also has a marked impact on the distribution laws of uplift pressure; and the lower the permeability is, the more obvious the distribution laws are. These research results will be the basis of further study on process and mechanism of uplift pressure acting on a bottom of check dam.