Simulation Experiment Research On Permeability Coefficient Of Direct Current Method Based On Sand Trough Model

The mathematical expression of groundwater movement in seepage field is (?),and the mathematical expression of current movement in electric field is(?).Based on the similarity of mathematical expressions describing the movement of water flow and current,through the simulation experiment of direct current method in homogeneous sand tank model,this paper studies(1)the distribution characteristics of current and potential under four conditions,such as zero water level difference in sand tank,water flow to negative pole,water flow to positive pole,increasing water level difference,and the correlation between physical quantities in the two formulas;(2)The influence of electrode and medium contact area,material,depth and N electrode position on current and potential;(3)The correlation between the current I_AB and the distance between the AB electrode and the water level of the sand box,the potential gradient and the distance between the observation point and the water level of the sand box,and the change of the potential gradient with the permeability coefficient of the medium.(4)Feasibility of calculating permeability coefficient by direct current method.The following research results are obtained:1.the water level difference in the sand box is zero,from A(positive pole)to B(negative pole),the sand sample at the observation point is saturated or unsaturated,and the potential decreases approximately in a straight line,and the potential gradient is basically unchanged.There is a certain water level difference in the sand box,the sand sample at the observation point is not saturated with water,and the potential gradient increases with the increase of the distance between the observation point and the water level;At the observation point,the sand sample is saturated with water,and the potential decreases nearly like a straight line,and the potential gradient remains basically unchanged.The sand samples at the observation point are not saturated with water,and the current I_AB increases with the increase of the water level in the sand box.After the sand samples on the AB connection line are all saturated with water,the current reaches the maximum constant.2.The current I_AB and potential increase with the increase of the contact area between the power supply electrode and the aqueous medium,but the contact area between the observation electrode and the medium has no obvious influence on the current and potential.The material of electrode has little influence on current and potential;The closer the N electrode is to the A electrode,the greater the potential difference between MN,and the potential gradient does not change;The greater the electrode insertion depth,the closer the distance to the water level of the sand box,and the greater the current and potential values.3.In the horizontal direction,there is no obvious correlation between potential and water level,potential gradient and hydraulic gradient,current and discharge.In the vertical direction,the electrode is located on the surface of the unsaturated sand layer,and when the water level difference in the sand box is zero,there is a negative linear correlation between the current I_AB and the distance between the AB electrode and the water level,I_AB=-0.097l+4.977,and the fitting degree R²=0.972,which is highly correlated;When there is a certain water level difference in the sand box,there is an exponential relationship between the potential gradient and the distance from the observation point to the water level,E=10.127e^0.050l,R²=0.854,and there is a high correlation between them.4.In a homogeneous aqueous medium,when the sand sample at the observation point is saturated with water,the potential gradient from A to B is constant,as the water level in the sand box rises,the potential gradient gradually decreases;when the water level is the same,the potential gradient increases with the increase of the permeability coefficient of porous media.The distribution characteristics of current,potential and potential gradient in artificial electric field are closely related to water level and permeability coefficient in medium.It is expected to obtain more hydrogeological information in the future by studying the correlation between parameters and using direct current method to calculate permeability coefficient.