Characterization of Karst Features Using Electromagnetics and Microgravity: A Strategic Approach

Yuhr, Lynn B.; Benson, Richard C.; Butler, Dwain K.

doi:10.4133/1.2921996

Cited by 12 publications

(7 citation statements)

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“…이들 탐사법 중에 지표부근의 공동탐지에 는 전기비저항 탐사 (Mark and Eric, 1999;Roth et al, 1999), 홍진표·지윤수·오석훈·최성웅 고정밀 중력 탐사 (Yuhr et al, 1993;Dourado et al, 2001), 탄 성파 탐사 (Park et al, 1999) (Fig. 3(a)).…”

Section: 지반침하의 주요 원인 중 하나인 지하공동을 조사하기 위하unclassified

A Geophysical Survey of Subsidence area around Limestone Mine Sites

Hong¹,

Ji²,

Oh³

et al. 2015

Geophysics and Geophysical Exploration

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Electrical resistivity surveys were conducted at two subsidence areas near and at limestone mine sites, respectively, in order to estimate their causes of subsidence and the regions of potential occurrence. In addition, the linkages of mine development with these subsidences were investigated by the rock engineering analysis. Two study areas have different geological setting. One study site is the land subsidence area, which contains clay and sandy soil near the limestone mine, The other study site is the land subsidence area located just above the mine, which is expected to be relevant to the limestone mine. As results of two-dimensional (2D) electrical resistivity surveys at the sites 1 and 2, low resistivity zones, which are 70 ~ 120 ohm-m and 20 ~ 50 ohm-m, respectively, were found under the subsidence zones. For the study site 1, the possibility of subsidence was confirmed by using three-dimensional (3D) inversion performed with 2D resistivity profiles. For the study site 2, the cause of the subsidence and the possibility of subsidence occurrence were confirmed by rock engineering computation with regard to measurement line 7 in which low resistivity accompanied by subsidence area was observed.

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Section: 지반침하의 주요 원인 중 하나인 지하공동을 조사하기 위하unclassified

A Geophysical Survey of Subsidence area around Limestone Mine Sites

Hong¹,

Ji²,

Oh³

et al. 2015

Geophysics and Geophysical Exploration

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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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“…The mapped sandstone caverns were 2 to 5 m in diameter and 40-50 m below the surface. Yuhr et al (1993) acquired a few gravity profiles over a known air-filled cave system in western Texas to detect the cavities, and combined the microgravity with electromagnetic techniques to locate dissolution enlarged joints above the karst. They also discussed the halo effect.…”

Section: Microgravity In Void Detectionmentioning

confidence: 99%

The detection of cavities using the microgravity technique: case histories from mining and karstic environments

Bishop

Styles

Emsley

et al. 1997

EGSP

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Th.e presence of mining-related cavities (workingS, shafts and tunnels) or karstic (solution cavities and sinkholes in limestone) within the top 100m in the rock mass restricts land utilisation, and their migration to the surface may damage property or services or cause loss of life. Confirmation of features marked on existing plans prior to design and construction may be sufficient but it is often necessary to determine the detailed sub-surface structure. The standard method of site investigation is to drill a pattern of boreholes to locate the spatial extent of any cavities. However, unless the spacing is less than the cavity dimensions it is possible to miss it completely. A cavity may be filled with air, water, or collapse material resulting in a contrast in physical properties which may be detected using appropriate geophysical methods. One powerful technique is microgravity which locates areas of contrasting sub-surface density from surface measurements of the earth's gravity. Although the method is fundamentally simple, measurement of the minute variations in gravity (1 in 108) requires sensitive instruments, careful data acquisition, and data reduction and digital data analysis. Final interpretation must be performed in conjunction with independent information about the site's history and geology. This paper presents three examples in both mining and karstic environments demonstrating that microgravity is a very effective technique for detecting and delineating cavities in the sub-surface.

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Characterization of Karst Features Using Electromagnetics and Microgravity: A Strategic Approach

Cited by 12 publications

References 0 publications

A Geophysical Survey of Subsidence area around Limestone Mine Sites

A Geophysical Survey of Subsidence area around Limestone Mine Sites

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

The detection of cavities using the microgravity technique: case histories from mining and karstic environments

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