颗粒级配影响滤层系统细颗粒迁移试验研究

Experimental study on fine particle migration in filter layer system affected by particle gradation

滤层是渗透破坏防治工程中的重要措施之一。利用自行研制的大型渗透仪,对不同滤层系统颗粒组成条件下的流失细颗粒的迁移规律进行了研究,并分析了层间系数D15/d85、不均匀系数Cu、控制粒径等对滤层有效性的影响。试验结果表明:当水力梯度在10以下时,层间系数在13以下滤层即可达到滤土作用,说明太沙基准则偏于安全。基料颗粒愈粗,临界及破坏水力梯度随层间系数的变化愈显著;基料颗粒愈细,流失细颗粒的运移规律对于层间系数的变化愈敏感,颗粒从起动到运移过程愈短,渗透破坏愈突然,愈不易防范。此外,基料颗粒Cu<1.86时,Cu越小,基料颗粒越不易起动;Cu>1.86时,起动临界水力梯度基本保持不变。当基料级配不变时,临界水力梯度与滤层颗粒粒径呈线性相关。

The filter layer is one of the important measures in hydraulic engineering,especially for controlling seepage failure.In this paper,the lost migration law of fine particles in different filter systems under different composition conditions of particles is studied by using a self-developed apparatus.The effects of the inter-layer coefficient D15/d85,the non-uniform coefficient Cu and the controlled particle size on the effectiveness of filter layer further analyzed.The results show that the hydraulic gradient is smaller than 10 and the inter-layer coefficient is smaller than 13 Terzaghi’s criteria is tend to be conservative.The coarser the base material particles are,the more significant the change of critical and failure hydraulic gradients with interlayer coefficient is.The finer the base material particles are,the more sensitive the migration law of the lost fine particles is to the change of the interlayer coefficient.The shorter the process from the start to the migration of particles,the more sudden the seepage failure is,which means that it is more difficult to prevent.In addition,the smaller the Cu content is,the more difficult it is to start the base particles when the Cu content of the base particles is less than 1.86.When Cu is above 1.86,the critical hydraulic gradient of start-up is basically unchanged.The critical hydraulic gradient is linearly related to the particle size of the filter as the gradation of the base material is constant.