Experimental Study Of Dispersion Coefficient And Scale Effect In Single Horizontal Fracture

The groundwater flow and solute transport in the fractured media hasbeen an important research aspect in hydrogeology. The study on water flow and solute transport in porous media at home and abroad has increasingly growns up,but some researches in fractured media remains need to be further improved, especially the research in laws of migration and transformation of pollutants.Based on the study about water flow and solute transport in the fractured media at home and abroad, a set of experiment equipment simulating groundwater flow and solute transport is designed. Here the test simulating groundwater flow and solute transport is performed in the single parallel plate fracture, the results are studied and analyzed, and the conclusions are drawn as followings:(1) In low flow areas (front-line flow area), the permeability coefficient increases as the aperture decreases.(2)Flow velocity and hydraulic gradient were fitted in low flow areas, the result was non-Darcy relations, fitting factor n values from 1 to 2, consisting with the factor value in high-speed non-Darcy flow gived by Zhou Zhifang .This shows that either a low speed or high-speed, the fitting factor n in non-Darcy flow is basically the same.(3) The law between the Peclet (Pe) number and DL / Df (the ratio of the vertical diffusion coefficient and the diffusion coefficient) in the single horizontal fracture is showed as following: D L Df= b+aPem, the m values between 1.0 to 2.0, larger than the range in porous medium obtained through experiment performed by Bear(1972). This is because that in the same case, diffusion coefficient in the porous medium is usually much smaller than the fracture, resulting in variation magnitude of DL / Df increases as Pe increases, m value relatively increases.(4) In the low flow stage, the fractal dimension of diffusion coefficient scale effect decreases as flow rate increases, diffusion coefficient decreases as aperture increases;(5) In Darcy flow ,dispersion decreases as the permeability coefficient increases.