Spatial and temporal instabilities in water flow through variably saturated fractured basalt on a one-meter field scale

Podgorney, Robert; Wood, Thomas R.; Faybishenko, Boris; Stoops, Thomas M.

doi:10.1029/gm122p0129

Cited by 17 publications

(25 citation statements)

References 30 publications

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“…Finally, we note that within a fracture–matrix network, several recent experiments conducted in the field have also shown temporal and some spatial dynamics suggestive of unsteady behavior even under reasonably long‐term steady supply conditions [e.g., Dahan et al , 1999; Faybishenko et al , 2000; Podgorney et al , 2000]. Such behavior is consistent in a general sense with what we have found in our mesoscale experiments within a controlled laboratory setting.…”

Section: Discussionsupporting

confidence: 90%

Unsaturated flow through a fracture–matrix network: Dynamic preferential pathways in mesoscale laboratory experiments

Glass

Nicholl

Pringle

et al. 2002

Water Resources Research

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[1] We conducted two laboratory experiments at the meter scale in which water was applied to the top of an initially dry, uncemented wall composed of porous bricks. One experiment (Experiment 1) encouraged evaporation and resulting mineral precipitation, while the other (Experiment 2) was designed to minimize these processes. In both cases, processes acting within the fracture network controlled early time behavior, forming discrete pathways and demonstrating fractures to act as both flow conductors and capillary barriers. At a later time, evaporation-mineral precipitation in Experiment 1 constrained flow, strengthening some pathways and starving others. In Experiment 2, the wetted structure took on the appearance of a diffuse plume; however, individual pathways persisted within the wetted structure and interacted, displaying erratic outflow over a wide range of timescales, including switching between pathways. Thus, under conditions of constant supply and both with and without evaporation-mineral precipitation, unsaturated flow through fractured rock can create dynamic preferential pathways.

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Section: Discussionsupporting

confidence: 90%

Unsaturated flow through a fracture–matrix network: Dynamic preferential pathways in mesoscale laboratory experiments

Glass

Nicholl

Pringle

et al. 2002

Water Resources Research

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“…At the one-to-tenmeter scale, several in situ experiments have investigated the interplay of fracture flow and fracture matrix interactions (e.g., Wang et al, 1999;Dahan et al, 1998;Podgorney et al, 2000). However, in each of these experiments, estimates of fracture flow and matrix imbibition remained largely unknown because some of the introduced water was able to bypass the monitoring system.…”

Section: Version 00amentioning

confidence: 99%

Fault-matrix interactions in nonwelded tuff of the Paintbrush Group at Yucca Mountain

Salve¹,

Oldenburg²,

Wang³

2003

Journal of Contaminant Hydrology

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To investigate the potential for fast flow through altered tuff of the nonwelded unit of the Paintbrush Group (PTn) at Yucca Mountain, Nevada, we carried out in situ field experiments using water released directly into the matrix and along a minor subvertical normal fault at Alcove 4 in the Exploratory Studies Facility. During the experiments, changes in moisture content were monitored within the test bed, and a slot excavated below the test bed was visually inspected for seepage. Our field tests suggest that the dry porous PTn matrix is capable of attenuating episodic percolation fluxes in localized areas (such as around faults) where fast flow would be expected to dominate.Once wetted, the matrix is able to retain the moisture over a period of months. As saturation increases in the matrix, less water imbibes along the fault and more water travels farther along the fault. From this observation, we infer that a sequence of infiltration events separated by periods of up to a few months could convey water over increasing distances along the fault.

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“…There is also a body of field evidence that shows rapid and deep penetration of fractured vadose zones by both meteoric water [e.g., Fabryka-Martin et al, 1996;Davidson et al, 1998], and fluid from ponded infiltration experiments [e.g., Glass et al, 2002b]. Additionally, several recent field experiments have shown temporal and spatial dynamics suggestive of complex unsteady behavior, sometimes under conditions of long-term steady supply or ponding [e.g., Dahan et al, 1999;Faybishenko et al, 2000;Podgorney et al, 2000]. While many of these large-scale field results could be inferred from physical processes acting in single fractures under conditions of unsaturated and two-phase flow [Glass et al, 1995[Glass et al, , 2001National Research Council, 1996], network effects have yet to be considered in detail.…”

Section: Introductionmentioning

confidence: 99%

Unsaturated flow through fracture networks: Evolution of liquid phase structure, dynamics, and the critical importance of fracture intersections

Glass

Nicholl

Rajaram

et al. 2003

Water Resources Research

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Experiments and analyses are presented to elucidate the critical control of fracture intersections on the evolution and dynamics of the liquid phase structure within unsaturated fracture networks in impermeable media. Phase structure was visualized within a thick vertical sheet of broken glass where the breaks constituted the fracture network. The critical system parameters, applied flow rate (viscous forces) and initial condition, were varied in a series of experiments. When initially dry, individual fracture intersections acted as capillary barriers and created a repeated dynamic from which a network‐scale “slender‐ladder” phase structure emerges that is composed of pools above each intersection joined by fingers or “tendrils” below. At low‐flow rates, pulsation is found at intersections, within fingers, and along horizontal fractures. In some cases, pulsation extends to larger volume “cascade” events where several intersections act in concert. At higher‐flow rates, viscous forces remove pulsation. Reinvasion upon drainage demonstrates that when initially wet, the capillary barrier behavior of the individual fracture intersections vanishes and intersections are rapidly spanned. This marked hysteretic response tends to guide flow and cause pathway persistence from one event to the next.

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Spatial and temporal instabilities in water flow through variably saturated fractured basalt on a one-meter field scale

Cited by 17 publications

References 30 publications

Unsaturated flow through a fracture–matrix network: Dynamic preferential pathways in mesoscale laboratory experiments

Unsaturated flow through a fracture–matrix network: Dynamic preferential pathways in mesoscale laboratory experiments

Fault-matrix interactions in nonwelded tuff of the Paintbrush Group at Yucca Mountain

Unsaturated flow through fracture networks: Evolution of liquid phase structure, dynamics, and the critical importance of fracture intersections

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