Experimental Study On The Effect Of Fracture Connectivity On Solute Transport

Fissure rock mass is a complex of rock and fissure.A large number of fissures in rock mass constitute the main passageway for groundwater flow and contaminant transport.The connectivity between fissures plays an important role in the study of groundwater flow and solute transport experimental study in this article,through analysis of characteristics of cracks and its effects on solute transport related,according to the different physical model experiment design,in view of the fracture connectivity and the size of the fracture of the regularity study of solute transport,according to the different test results were analyzed,for different fracture connectivity and fissure angle of sight to the influence laws of solute transport,mainly from the following conclusion:(1)According to the hydrodynamic test of different fracture models,the flow of dead-end fractures with five kinds of intersection angles at low speed basically conforms to darcy's law.When the flow velocity of dead-end fractures with five kinds of intersection angles is more than 10cm/s,the hydraulic gradient and the flow velocity no longer conform to the linear relationship.The V-J fitting curve of the connected fracture is well fitted under the condition of quadratic function equation.(2)According to the five dead-end fracture model tests,hydraulic losses in different fracture models are also different with the change of flow velocity,and the losses are greatly different.Compared with the hydraulic losses in dead-end fractures,the hydraulic losses in the connected fractures with three angles are slightly different.At the same flow rate,the hydraulic loss of the crack at the 30-degree angle dead end is the largest,and with the increase of the angle,the hydraulic loss gradually decreases.(3)In the early stage,the solute in the dead-end crack was transported out of the dead-end crack by the convection action of the flow inertia force.At the following moment,the depth of the dead-end crack affected by the inertial force is limited,and the solute gradually moves to the action area of the flow inertial force under the action of molecular diffusion from a deeper position.The solute is transported by convection leaves the dead-end crack with the mainstream channel.This stage is dominated by convection and diffusion.In the later stage,if there is no molecular diffusion,the solute will not diffuse from inside the dead-end crack to the exit and migrate away with the water flow acted by the inertial force.This stage is dominated by molecular diffusion.(4)The intersection angle between the dead-end crack and the mainstream channel has a great influence on solute migration out of the dead-end crack.With the increase of velocity,the solute in the dead-end crack with an angle less than 90 degrees varies greatly under the influence of velocity.The solute in the dead-end fracture with an angle greater than 90 degrees is less affected by the flow rate.(5)Compared with the other two kinds of scenarios,the solute transport in the 90 degree connected fracture intersection angle scenario was slower in the early stage,and showed higher and more obvious solute drag phenomenon.At the late stage of solute transport in the connected fractures,the solute at the dead corner of the connected fractures is difficult to move out with the water flow,while the solute at the dead corner diffuses out mainly through molecules.