J. Guimera et J. Carrera, A comparison of hydraulic and transport parameters measured in low-permeability fractured media, J CONTAM HY, 41(3-4), 2000, pp. 261-281
Data from 90 tracer experiments performed in low-permeability fractured med
ia have been studied to explore correlations among parameters controlling f
low and transport, The original data had been interpreted by different auth
ors using different models, which prevents direct comparison of their estim
ated parameters. In order to produce comparable parameters, the data have b
een reexamined using simple models (homogeneous domain, steady-state flow r
egime, single porosity). Specifically, hydraulic conductivity has been deri
ved as the ratio of water flux:to head gradient and apparent porosity as th
e ratio of water velocity to water flux; the former estimated from both fir
st and peak arrival times, Hydraulic conductivity and porosity correlate al
ong a straight line of slope 1:3 in log scale. While the regression is too
noisy to be of predictive use, it lends some support to the use of a genera
lized cubic law. The fact that correlation for Gst arrival time porosity (0
.77) is larger than for peak arrival porosity (0.62) suggests that first ar
rival is controlled by the same flow paths as hydraulic conductivity. Appar
ent porosity derived from peak arrival time is found to grow with travel ti
me along a line of 0.55 slope (again log scale). The correlation coefficien
t ranges between 0.73 and 0.80 (depending on the data set) for hard:rocks.
The fact that this correlation is maintained when varying the flow rate at
a given site leads us to suggest that it is caused by diffusion mechanisms.
This conclusion is further supported by the increase of apparent porosity
with the matrix porosity of the rock on which the experiments were performe
d. (C) 2000 Published by Elsevier Science B.V. All rights reserved.