A Summary of Methods for Locating and Mapping Fractures and Cavities with Emphasis on Geophysical Methods

Benson, Richard C.; Yuhr, Lynn B.

doi:10.4133/1.2921955

Cited by 7 publications

(10 citation statements)

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“…The investigation of a small sink feature causing soil piping adversely affecting a residential building footer will require a different scale of geophysical information than the design needs for a proposed shopping mall in a karst setting. The need to scale the geophysical method to the size of the problem becomes an important consideration (Benson, 1992).…”

Section: Methodsmentioning

confidence: 99%

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Geophysical Choices for Karst Investigations

Hoover

2003

Sinkholes and the Engineering and Environmental Impacts of Karst

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It is not unusual for a geologist or engineer to be called upon to investigate and address problems related to sinkholes in karst environment. Sinkholes in a karst environment can be a dream, or nightmare. Most professionals know that geophysics can help, but the geophysical method and parameters that may be best suited for the problem at hand are a less certain choice. Geophysical technology and standards have evolved tremendously over the last 10-years. This paper briefly examines geophysical standards that have been developed. A discussion of the methods that are commonly applied to karst investigations, the advantages and disadvantages of the methods, acquisition parameters, and the kinds of results to be expected will be presented. Common geophysical methods to be examined in detail include electromagnetic terrain conductivity, gravity, electrical imaging and seismic.

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Section: Methodsmentioning

confidence: 99%

“…Seismic refraction methods measure the velocity of energy transmitted through the soil and rock. Typical seismic velocities range from 500 to 6,000 feet per second for soils, and 6,500 to 18,000 feet per second for bedrock (Haeni, 1984). Lower soil velocities can be expected when unconsolidated soils are present near sinkhole features.…”

Section: Seismicmentioning

confidence: 99%

Geophysical Choices for Karst Investigations

Hoover

2003

Sinkholes and the Engineering and Environmental Impacts of Karst

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“…Numerous papers, government agency reports, company reports, and textbooks have examined the effectiveness of geophysical methods applied to cave detection (e.g., Frohlich and Smith, 1977;Greenfield, 1979;Kirk and Werner, 1981;Milanovic, 1981;Owen, 1983;Day and Wagener, 1984;White, 1988;Benson and Yuhr, 1992;Boulding, 1993;Yuhr et al, 1993). Relatively few papers, however, have focused on geophysical detection of buried sinkholes or other epikarstal features.…”

Section: Previous Geophysical Studies Of Karst Featuresmentioning

confidence: 99%

Geophysical Character of Buried Sinkholes on the Oak Ridge Reservation, Tennessee (Presented at SAGEEP95 in Orlando, FL)

Carpenter¹,

Doll²,

Kaufmann³

1998

JEEG

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Sinkholes are important near-surface indicators of active karst features at depth, such as cavities, conduits and solutionally-enlarged fractures. This study tests the hypothesis that ground-penetrating radar (GPR) and other geophysical methods may be used to identify filled sinkholes as a means of inferring the existence of these deeper hydraulically-active karst features. Geophysical surveys were made at two sites in Bear Creek Valley on the Oak Ridge Reservation in eastern Tennessee. GPR profiles (25 and 50 MHz) made along the northeast edge of Bear Creek Valley showed a troughlike pattern of radar reflections outlining a possible filled sinkhole. This feature is at least 45 m wide, 3.5 to 5 m deep, and appears on GPR profiles acquired at a variety of antenna separations and along profiles made in different directions. Its dimensions are consistent with dimensions of other mapped sinkholes in the area. GPR, electromagnetic conductivity surveys, resistivity soundings and gravity models suggest this feature is filled with relatively dense, resistive residuum or colluvium, and may contain cherty gravels along its base and sides. This structure lies almost directly above a major hydraulically-active bedrock cavity at a depth of 18 m that was encountered during drilling of a nearby monitoring well. Similar reflection patterns were recorded by GPR surveys over another filled sinkhole at this site, and by GPR profiles over possible filled sinkholes above active karst conduits at a second site 7 km to the southwest.

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“…Very often a cave system at depth (may be beyond the range of our measurement) but will show signs of its presence and possible activity by NSI or halos within the shallow sediment or rock. These NSI or halo effects may include: -Soil piping, raveling or dipping strata that may be occurring in the shallow sediment as a result of a deep collapse, which has not yet reached the surface (Benson and Yuhr 1992 ). -A fracture system over a cave may have caused a local increase in permeability and provide an area of groundwater recharge resulting in geochemical changes over the cave.…”

Section: Direct and Indirect Detection Of Anomalous Conditionsmentioning

confidence: 99%

“…-A fracture system over a cave may have caused a local increase in permeability and provide an area of groundwater recharge resulting in geochemical changes over the cave. As a result, a local change in electrical conductivity, resistivity, or SP voltage may provide an indication of the presence of an underlying cavity (Benson and Yuhr 1992 ). -Thermal gradients or fl owing air may exist at the surface, associated with permeable zones, fractures or caves within the unsaturated zone (Thompson and Marvin 2006 ;Straley 2008 ;Bogle and Loy 1995 ;Campbell and Singer 2001 ).…”

Section: Direct and Indirect Detection Of Anomalous Conditionsmentioning

confidence: 99%

Surface Geophysical Methods

Benson¹,

Yuhr²

2016

Site Characterization in Karst and Pseudokarst Terraines

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We now have a work plan that is based upon regional and local existing data and possibly some site-specifi c data. A conceptual model has been developed and focuses our attention on what we know, what we need to know and what we might expect on site. As we begin to acquire on-site data using surface geophysical methods, we will begin to test the conceptual model. Their primary benefi t is that of greatly increasing the data density over the site, which improves the defi nition of background and anomalous conditions. These measurements allow us to more accurately locate invasive measurements based upon data rather than guesses thereby improving the chances of accurately defi ning geologic conditions. This section provides an introduction to the many surface geophysical methods. We have focused on considerations for their use and how to select methods rather than how to make the measurements. In addition, a large number of examples showing their application are provided to show how these methods can be used in a site characterization effort.

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A Summary of Methods for Locating and Mapping Fractures and Cavities with Emphasis on Geophysical Methods

Cited by 7 publications

References 0 publications

Geophysical Choices for Karst Investigations

Geophysical Choices for Karst Investigations

Geophysical Character of Buried Sinkholes on the Oak Ridge Reservation, Tennessee (Presented at SAGEEP95 in Orlando, FL)

Surface Geophysical Methods

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