Measurement of 3‐D Hydraulic Conductivity in Aquifer Cores at In Situ Effective Stresses
46
Citation
9
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract An innovative and nondestructive method to measure the hydraulic conductivity of drill core samples in horizontal and vertical directions within a triaxial cell has been developed. This has been applied to characterizing anisotropy and heterogeneity of a confined consolidated limestone aquifer. Most of the cores tested were isotropic, but hydraulic conductivity varied considerably and the core samples with lowest values were also the most anisotropic. Hydraulic conductivity decreased with increasing effective stress due to closure of microfractures caused by sampling for all core samples. This demonstrates the importance of replicating in situ effective stresses when measuring hydraulic conductivity of cores of deep aquifers in the laboratory.Keywords:
Permeameter
Permeameter
Hydraulic head
Cite
Citations (3)
Abstract The direct‐push permeameter (DPP) is a promising approach for obtaining high‐resolution information about vertical variations in hydraulic conductivity ( K ) in shallow unconsolidated settings. This small‐diameter tool, which consists of a short screened section with a pair of transducers inset in the tool near the screen, is pushed into the subsurface to a depth at which a K estimate is desired. A short hydraulic test is then performed by injecting water through the screen at a constant rate (less than 4 L/min) while pressure changes are monitored at the transducer locations. Hydraulic conductivity is calculated using the injection rate and the pressure changes in simple expressions based on Darcy’s Law. In units of moderate or higher hydraulic conductivity (more than 1 m/d), testing at a single level can be completed within 10 to 15 min. Two major advantages of the method are its speed and the insensitivity of the K estimates to the zone of compaction created by tool advancement. The potential of the approach has been assessed at two extensively studied sites in the United States and Germany over a K range commonly faced in practical field investigations (0.02 to 500 m/d). The results of this assessment demonstrate that the DPP can provide high‐resolution K estimates that are in good agreement with estimates obtained through other means.
Permeameter
Cite
Citations (99)
This study investigates the performance of bentonite components of geosynthetic clay liners (GCLs) when exposed to aggressive leachates using the fluid loss test and provides a possible quick method for estimating the effect of acidic conditions on hydraulic conductivity. Fluid loss generally increases with increasing acid concentrations. Hydraulic conductivity values back-calculated from the fluid loss tests (k FL ) are compared with the values measured using a flexible-wall permeameter (k Tri ). Generally, the predicted hydraulic conductivity values are conservative (k FL /k Tri > 1) under water and low acid concentrations (≤0.015 mol/L). However, the back-calculated hydraulic conductivity is shown to be nonconservative (k FL /k Tri < 1) at high acid concentrations (≥0.125 mol/L).
Permeameter
Geosynthetic clay liner
Bentonite
Geosynthetics
Hydraulic head
Slug test
Cite
Citations (47)
A modified apparatus that permits measurement of hydraulic conductivity of undisturbed soil cores in the laboratory is described. In this technique the two traditional errors, i.e., side flow and destruction of soil structure, are simultaneously controlled. The results obtained are significantly lower and more realistic than those of the traditional technique.
Permeameter
Cite
Citations (4)
This paper presents a series of field double-ring infiltration tests (DRTs) for investigating the hydraulic conductivity of a compacted silty clay fill that contains some desiccation cracks. These field tests were conducted at three different depths in the fill, to characterise the variations of conductivity with depth. The hydraulic conductivity of the fill was also measured in the laboratory on block samples using a three-directional permeability cell (sample size: 200 mm × 200 mm × 200 mm) and a one-dimensional permeameter (sample size: 70 mm in diameter and 45 mm high). A perched water table was detected in the fill using tensiometers shortly after the start of each DRT, showing the presence of preferential flow paths in the fill. The hydraulic conductivity decreases with increasing depth. The larger hydraulic conductivity of the surface soil indicates the possible presence of macropores and cracks at shallow depths of the fill. The coefficients of variation of the hydraulic conductivity measured from the DRTs (influence volume: 300 mm in diameter and 450 mm high) and the three-directional permeability cell tests are smaller than those measured from the small-size, one-dimensional permeameter tests. The variability of the measured hydraulic conductivity increases as the sample size decreases.
Permeameter
Infiltrometer
Macropore
Infiltration (HVAC)
Cite
Citations (16)