竖向及水平向渗流作用下粉砂渗透特性研究

Permeability characteristics of silty sand under vertical and horizontal seepages

采用自主研制的圆柱形渗流仪及水平渗流装置,开展了粉砂竖向和水平向的渗流试验,获取了两种渗流方向下粉砂的临界水力梯度及其渗透变形特性。在级配、密度、孔隙大小等影响因素相同的前提下,粉砂竖向渗流的临界水力梯度比水平向高出近44%,水平向渗流作用一般高于竖向。基于室内试验成果,采用离散元与计算流体力学耦合的细观力学模型,对粉砂在竖向和水平向的渗流情况进行分析和模拟。结果表明,粉砂的渗透变形拐点与模型试验结果吻合,水平渗流和竖向渗流分别在水力梯度i=0.8,0.4时出现颗粒簇的流失,在水力梯度分别为1.0和0.5时发生整体渗透破坏。

The influence of seepage direction on the silt permeability are studied.The vertical and horizontal seepage tests of silty sand are carried out by using the self-designed devices.The critical gradient and deformation characteristics of silt under two different seepage directions are obtained in the tests.When the other influencing factors such as gradation,density and pore size are the same,the vertical hydraulic gradient of horizontal seepage of silt is generally 44%higher than the critical one,and the horizontal seepage is generally higher than the vertical one.The data can be used for design of seepage control of the silt.Based on the indoor model tests,the micro-mechanical model is used to analyze and simulate the seepage behavior of the silt under vertical and horizontal directions.The hydraulic gradients of the two seepage directions calculated by numerical model are consistent with the test ones.The loss of particle clusters occurs in horizontal and vertical seepages at hydraulic gradients of 0.8 and 0.4,respectively.The research results may provide a theoretical basis for the design of seepage control in water conservancy and hydropower projects with silt layer.