Experiment Study Of Preferential Flow And Solute Transport In Cross Fracture

With the increasing number of underground engineering,especially the nuclear waste disposal project,the demand for water and solute transport in the bedrock fissure is becoming more and more important.The cross fracture is an important part of the fracture network.It is of great significance to study the pollution and prevention of deep groundwater by the study of the cross fissure flow and solute transport.Based on the current research status of flow and solute transport in fissure at home and abroad,the influence of the preferential flow channel on the flow and solute transport in the cross fracture is analyzed.An experimental device for simulating the dominant flow and solute transport in the cross rough fracture is designed and manufactured.The simulation experiment of the dominant flow and solute transport in the cross rough fracture is carried out.The characteristics of heat and solute transport are preliminarily discussed by analyzing the dominant flow laws of cross fissures.The main conclusions are as follows:(1)Under the condition of this experiment,a cross point of the local fracture flow velocity V and hydraulic gradient J is nonlinear,and the average deviation of Darcy's law,the traditional meaning,while the Forchheimer formula can better fit the relationship between the hydraulic gradient and flow velocity,higher fitting precision.;The relationship between the single width flow and the hydraulic gradient is q=KJ~m,and the value of m increases with the increase of relative roughness.;The traditional local cube law does not apply to rough fractures.The corrected cubic law can better match the measured data.The n value of gap width index is greater than 3,which belongs to the super cube law.And the n value decreases with the increase of roughness.(2)The preferential flow effect in the cross rough fracture is affected by the fracture roughness and the angle of inlet and outlet.In the two groups of fracture with different roughness,the bigger the difference of fracture roughness is,the stronger the advantage flow effect is.(3)Comparing the influence of dominant effect on heat migration under different roughness conditions,it is found that the difference of peak value of breakthrough curve at the same position within two ends of water cracks increases with the increase of dominance effect in the first two groups.(4)The peak value of heat breakthrough curve at different locations across the fracture intersection has a significant gap and does not decrease with the increase of migration distance.The maximum breakthrough curve mostly occurs at the probe point3 and the probe point 4 position,and the probe point 4 is more.It is shown that the solute mixing mode at the intersection point is between the linear model and the completely mixed mode.(5)The change of heat transfer through the peak arrival time is caused by the injection of different heat fluid,and the peak arrival time is gradually delayed with the increase of the injection amount.The peak time gap tends to decrease with the increase of velocity.It shows that there is interaction between the temperature field and the coupling condition of the seepage field.(6)Blue tracer solute breakthrough curve by ADE and TPL two kinds of model fitting,the result showed that the fitting precision of TPL model is better,the breakthrough curve fitting curve and tailing phenomenon more consistent with measured values.