Comparison of Neutron Moisture Gauges and a Neutron Tool for Use in Monitoring Wells

Bishop, C. W.; Porro, I.

doi:10.1111/j.1745-6584.1997.tb00098.x

Cited by 3 publications

(2 citation statements)

References 4 publications

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“…Changes in the moisture regime were determined using neutron logging, time domain reflectometry (TDR), and ground-penetrating radar (GPR). It appears that the absolute value of the moisture content in fractured rocks cannot be determined from field measurements using these techniques because it is difficult, if not impossible, to obtain calibration curves for fractured rocks [Bishop and Porro, 1996]. Therefore we interpret relative increases in neutron counts and electromagnetic wave travel times as identifying zones of increased moisture content and use them to locate zones of preferential flow.…”

Section: Main Characteristics Of Flow and Transportmentioning

confidence: 99%

Conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone

Faybishenko¹,

Doughty²,

Steiger³

et al. 2000

Water Resources Research

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[1998]. They designed a compartmental liquid sampler, which was inserted into a horizontal borehole, to collect infiltrating solution at multiple locations. They estimated the amount of water flowing through the fractures and imbibing into the matrix across the fracture walls and determined that under variable moisture content conditions the fracture aperture, roughness, and flow channels varied with time. They also noted that under field conditions the effective fracture aperture was more than 1 order of magnitude smaller than that expected based on laboratory conditions. Or and Ghezzehei [2000] studied water dripping into subterranean cavities in a fractured porous medium in order to improve estimates of dripping rates onto waste disposal canisters placed in caverns. These results suggest that conventional approaches and concepts, such as Darcy flow through a constant fracture aperture, may not be valid for characterizing unsaturated fractured rocks.Several laboratory-scale investigations were conducted using natural fracture cores and fracture replicas to investigate factors and processes affecting flow and transport under con- In 1996, three groups of 16 wells were drilled to install monitoring instrumentation, including vertical wells of series T (depths of 3-6.7 m), and inclined wells (270-45 ø from vertical) of series E and R (lengths of 18.3-22.9 m). In 1997, after interpretation of the results of the 1996 infiltration test, which showed a zone of preferential flow between wells R1 and R2, two additional inclined wells (R5 and R6) were drilled between existing R wells. Note that inclined boreholes were mostly drilled from the outside of the pond to reduce the disturbance to the pond surface and to intersect more vertical columnbounding fractures to better characterize the three-dimensional geometry of flow below the pond.The types of instrumentation used during the infiltration tests are summarized in Table 1. A more detailed description of the instrumentation is given by Faybishenko et al. [1998b]. All the instruments were installed in boreholes using the following method of borehole completion [Faybishenko et al., 1998d]. The instruments were attached to the outer faces of polyethylene packers mounted onto sections of 3.5-crn OD PVC manchette pipe, and the sections were glued together to form a continuous string of instruments placed at preselected depths. After the string with the probes was lowered into a borehole, the packers and the space between the packers were infilled with impermeable polyurethane resin, thus pressing the instruments against the borehole walls. This completion method ensured that no water flow occurred through the bore- small trench (15 cm high by 15 cm wide) was cut into the basalt at the location of the previous berm and a permanent concrete wall was constructed that practically eliminated water leakage beneath and through the berm. The experimental data and fitting curves are shown in Figure 6, and the fitting parameters for each test, which were determined using a lea...

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Section: Main Characteristics Of Flow and Transportmentioning

confidence: 99%

Conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone

Faybishenko¹,

Doughty²,

Steiger³

et al. 2000

Water Resources Research

View full text Add to dashboard Cite

show abstract

“…It appears that the absolute value of the moisture content in fractured rocks cannot be determined from field measurements using these techniques because it is difficult, if not impossible, to obtain calibration curves for fractured rocks [Bishop and Porro, 1996].…”

Section: Main Characteristics Of Flow and Transport During The Infilt...mentioning

confidence: 99%

Conceptual Model of the Geometry and Physics of Water Flow in a Fractured Basalt Vadose Zone: Box Canyon Site, Idaho

Faybishenko

Doughty

Steiger

et al. 1999

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A conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone was developed based on the results of lithological studies and a series of ponded infiltration tests conducted at the Box Canyon site near the Idaho National Engineering and Environmental Laboratory (INEEL) in Idaho. The infiltration tests included one two-week test in 1996, three two-day tests in 1997, and one four-day test in 1997. For the various tests, initial infiltration rates ranged from 4.1 cm/day to 17.7 cm/day and then decreased with time, presumably due to mechanical or microbiological clogging of fractures and vesicular basalt in the near-surface zone, as well as the effect of entrapped air. The subsurface moisture redistribution was monitored with tensiometers, neutron logging, time domain reflectrometry and ground penetrating radar. A conservative tracer, potassium bromide, was added to the pond water at a concentration of 3 gIL to monitor water flow with electrical resistivity probes and water sampling. Analysis of the data showed evidence of preferential flow rather than the propagation of a uniform wetting front. We propose a conceptual model describing the saturationdesaturation behavior of the basalt, in which rapid preferential flow through vertical column-bounding fractures occurs from the surface to the base of the basalt flow. After the rapid wetting of column-bounding fractures, a gradual wetting of other fractures and the basalt matrix occurs. Fractures that are saturated early in the tests may become desaturated thereafter, which we attribute to the redistribution of water between fractures and matrix. Lateral movement of water was also observed within a horizontal central fracture zone and rubble zone, which could have important implications for contaminant accumulation at contaminated sites.

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Multi-Scale Investigations of Liquid Flow in a Fractured Basalt Vadose Zone

Faybishenko

Witherspoon

Doughty

et al. 2013

Flow and Transport Through Unsaturated Fractured Rock

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This paper introduces an approach to the problem of characterizing flow and transport in a fractured basalt vadose zone. We propose the development of physically based conceptual models on a hierarchy of scales. This approach is derived from field investigations that were conducted in the vadose zone of the Snake River Plain in southeastern Idaho. Three scales of ponded infiltration tests were carried out: a Large Scale Infiltration Test (LSIT) conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) (pond area •26,000 m2), intermediate-scale infiltration tests (pond area 56 m 2) conducted at the Box Canyon site (near Arco, Idaho), and small-scale infiltration tests (pond area 0.5 m 2) con-ducted at the Hell's Half Acre Lava Flow Site (near Shelly, Idaho). Laboratory water-dripping experiments were also conducted using fracture models with constant and variable apertures. We find that, at each scale of investigation, different models for flow phenomena must be used to explain the observed behavior. These models can be used to describe the flow processes on different scales, with no apparent scaling principles evident. To characterize flow phenomena in fractured basalt, we recommend that investigations be carried out at four scales: elemental, small-scale, intermediate-scale, and large-scale. An elemental component is a single fracture or a block of homogeneous porous media. Small-scale components include one or a few fractures and the surrounding matrix. Intermediate-scale (mesoscale) components include a basalt flow with its fracture network and other parts (fracture zones, vesicular lenses, soil, massive basalt, rubble zone) of a single basalt flow. Large-scale (regional) components include multiple basalt flows and their surrounding network of rubble zones and sedimentary interbeds.

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Comparison of Neutron Moisture Gauges and a Neutron Tool for Use in Monitoring Wells

Cited by 3 publications

References 4 publications

Conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone

Conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone

Conceptual Model of the Geometry and Physics of Water Flow in a Fractured Basalt Vadose Zone: Box Canyon Site, Idaho

Multi-Scale Investigations of Liquid Flow in a Fractured Basalt Vadose Zone

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