水流作用下裂隙内沉积颗粒起动临界流速研究

Study on the threshold velocity of sedimentary particle incipient motion in fracture under the action of water flow

为了优化阻塞裂隙的水力冲刷工艺参数,采用物理试验和理论分析相结合的方法,建立了水流作用下颗粒起动有效作用流速数学模型,研究了水流作用下裂隙内不同形状颗粒的起动方式和颗粒起动临界流速随颗粒粒径、流体密度和裂隙高度的变化特性。结果表明:近圆颗粒和椭球颗粒主要以滚动方式起动,扁平颗粒以滑动方式起动;颗粒起动临界流速随颗粒粒径的增大呈现对数增大的变化规律,随流体密度的增大呈减小的变化规律;进一步地,由于颗粒起动有效作用流速与裂隙高度的增大呈负相关的变化规律,因此颗粒起动临界流速随裂隙高度的增大而增大。为提升阻塞裂隙的水力冲刷效果,应采用的方法是增加流体介质的密度,促使裂隙内更多的沉积颗粒发生起动。此外,当水力冲刷工艺运用至裂隙发育的地带时,应该适当提高水力冲刷工艺的注水量,提高堵塞裂隙的水力冲刷工艺效果。

In order to optimize the hydraulic scouring process parameters of blocked fracture,a mathematical model of particle incipient motion effective velocity under the action of water flow was established,and the incipient motion of particles with different shapes in the fracture under the action of water flow and the variation of the particle incipient motion threshold velocity with particle size and fluid density as well as fracture height were studied by physical experiment method and theoretical analysis method.The results show that the near-circular and ellipsoidal particles get into motion mainly by rolling,and the flat particles get into motion by sliding.The threshold velocity of particle incipient motion shows a logarithmic increase with the increase of particle size and exhibit the decrease trend with the increase of fluid density.Furthermore,due to the negative correlation between the particle incipient motion effective velocity and the fracture height,the threshold velocity of particle incipient motion increases with the increase of fracture height.To enhance the hydraulic erosion effect of blocking fractures,the method for increasing the fluid density should be adopted to promote the more particles to get into the incipient motion.In addition,when hydraulic erosion technology is applied for the blocking fracture with the developed fractures,the water injection volume should be appropriately increased to improve the effectiveness of hydraulic erosion technology.