单裂隙承压无压条件下达西-非达西流演变试验研究

Experimental Study on Transition from Non-darcian to Darcy Flow under a Confined-unconfined Condition in Single Fracture

基岩裂隙水运移机理研究对基岩裂隙水水害防治以及污染修复具有重要意义。本文设计了由水泥和粗砂(粒径介于1mm^2mm之间)制成的单裂隙模型,开展了承压无压条件下基岩裂隙水流试验和拟合研究,讨论了水力梯度和流速之间的关系以及Forchheimer公式中线性项和非线性项的比例变化。得出主要结论如下:(1)实验条件下的水流呈非达西流,用Forchheimer公式可以较好地拟合水力梯度和流速的关系,且拟合精度较高。(2)随着离出水口距离的增加,水流从非达西流向达西流演变,当距离足够远时可以将水流视为达西流。(3)在水流从非达西流向达西流演变过程中,临界雷诺数随着隙宽的增加逐渐减小。

The transport mechanism of groundwater flow in fractured media has a significant impact on the remediation of bedrock fracture water disaster and pollution repair .This study designs a single fracture model made of a mixture of cement and coarse sands （diameters between 1 .0 mm and 2 .0 mm） ,conducts a series of hydraulic tests under the conditions of confined-unconfined flow .The relationship between hydraulic gradient and flow rate of different points and the proportion evolution of the linear and nonlinear portion in Forchheimer formula were discussed respectively .Main conclusions are drawn：（1） Non-darcian flow presents under this single fracture experiment condition .Better fitting accuracy is obtained by using Forchheimer formula than Darcy＇s law . （2） The transition from non-Darcian to Darcy flow has an increase trend with the observation scale enlargement .When the distance is far enough ,it can be seen as the Darcy flow .（3） During the transition from the non-Darcian to Darcy flow ,the critical Reynolds number decreases with the fracture aperture increasing .