RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS<sup>1</sup>

Casten, U.; Gram, C.

doi:10.1111/j.1365-2478.1989.tb01822.x

Cited by 14 publications

(8 citation statements)

References 9 publications

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“…Please note that h axis is displayed in a logarithmic scale. 0.05, 0.7 and 1.3 m, respectively; Antonov et al (1996) made use of towers with the heights of 0.75 and 0.9 m; Casten and Gram (1989) used a tripod with lower level at 0.3 m and upper level at 1.8 m; Butler (1984b), except of the zero level, measured at 0.60, 0.78 and 1.38, occasionally also at 1.63 m; Ager and Liard (1982) used the vertical separation of 0.876 m between their two measuring platforms. Earlier prevailed greater vertical separations, namely Fajklewicz (1976) writes about extensive measurements in Poland with the tower height 3 m, Janle et al (1971) were using approximately 4 m, Kumagai et al (1960) more than 5 m and Thyssen- Bornemisza and Stackler (1956) approximately 3.8 m. The recently adopted vertical distance of about 1 m is required for practical reasons, namely for the attainable accuracy of the measurements.…”

Section: Figmentioning

confidence: 99%

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

et al. 2015

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It is well known that the vertical gradient of gravity measured on the Earth's surface depends strongly on nearby topographical shapes. We simply inverted the problem and posed the question whether a zero vertical gradient can be observed using relative gravity meters and the classical tower method of measurement in appropriate terrain conditions. Extensively using the model of a vertical cone to simulate the real in-field conditions, we have found that reversed-cone-shaped topographic depressions represent the most perspective forms, which can contribute to extremely small values of the resulting vertical gradient. In one such form, namely a karstic sinkhole, we measured the value of 0.071 mGal/m (10 5 s 2 ). In addition, we successfully modeled this value using a detailed local digital elevation model. We thus conclude that zero vertical gradient of gravity should be observable by common means, also on the Earth's surface, and not only underground within very dense rocks as some ores can be. Once this is verified it could represent a contribution to the theory of the Earth's gravity field and its geophysical as well as geodetic applications.K e y w o r d s : normal gravity gradient, synthetic topography model, relative gravity measurement, tower method, sinkhole

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Section: Figmentioning

confidence: 99%

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

et al. 2015

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“…This difficulty can be removed either by locating gravity profiles in the galleries running both above and below the exploitation area or by the combined observation of gravity and its vertical gradient (tower gradient) at the same profile (Fajklewicz and Jakiel 1989). Measurement and interpretation of the vertical gradient of gravity for this purpose have been discussed by Fajklewicz, Glinski and Sliz (1982) and Casten and Gram (1989). If it is not possible to carry out one of these measurements near the region of interest, then the mining engineers can supply information about the location of the exploitation process relative to the position of the gravity profile.…”

Section: Igai-(i-l) = Agi -Agi-(i-i)mentioning

confidence: 99%

“…The mining reduction is computed to eliminate the changes of the vertical component of gravity attraction of the mass deficiency, which generally increases due to the mining exploitation. Both reductions were computed by applying the method of Gotze and Lahmeyer (1988) for 3D modelling (Casten and Gram 1989).…”

Section: Data Reductionmentioning

confidence: 99%

INDUCED GRAVITY ANOMALIES AND ROCK‐BURST RISK IN COAL MINES: A CASE HISTORY¹

Casten

Fajklewicz

1993

Geophysical Prospecting

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The use of the gravity method to predict rock bursts in mines is based on the relationship between the development of a dilatancy process in the exploited rock mass and the time‐dependent gravity anomalies induced by this phenomenon. The differences between successive observations of anomalies and the time behaviour of their trend amplitudes as precursors of preceding changes of rock stability are interpreted. The centres of zones of induced rock density variation are determined by computing the position of singular points of the differences between anomalies. Two gravity surveys have been carried out in the Radbod coal mine (Germany). The first survey took place at the level of the Dickebank seam (depth 1030 m), the second in the Sonnenschein seam (depth 1090 m). The observations were made with Worden and LaCoste‐Romberg (D‐type) gravimeters. The differences between successive anomalies were less than 100 μGal. In the case of the Dickebank seam, the position of singular points demonstrates the effect of two approaching longwalls on a previously mined‐out seam and on the gallery in which the gravity observations were made. In the case of the Sonnenschein seam, the trend amplitudes show distinct variations in the formation of the approaching longwall below the edges of all previously mined‐out seams. In particular, the effect of a remnant pillar has caused the largest gravity gradients. This result corresponds to the existence of a zone of rock‐burst hazard known from test drilling. The computed singular points are grouped together under the remnant pillar indicating two local hazard zones. Both results, the observed development of rock instability with time and the information about the position of the disturbed rock mass relative to the mine workings, are of importance, subsurface gravity surveying can therefore be a valuable tool for predicting rock‐bursts.

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“…Differences were taken which can be observed in a very short time, so tidal effects can be neglected and drift behaviour can be assumed to be linear and therefore also negligible. Differences were measured along the vertical calibration line of the Bochum University (southern staircase of the building NA) and with a mobile tower was used for underground vertical gradient observations (Casten and Gram 1989). Multiple observations of these differences were made, each consisting of five (calibration line) or three (tower gradient) repeats.…”

Section: Accuracy Of Gravity Differencesmentioning

confidence: 99%

“…There are four reasons for this. Firstly, there is the development of new methods such as mining gravimetry (Casten and Gram 1989) and archeological gravimetry (Lakshmanan and Montlucon 1987). Secondly, high precision is required in dynamic surveys which involve continuous monitoring of small gravity changes with time, such as those associated with mining-induced effects (Casten and Fajklewicz 1986) or active volcanic (Rymer and Brown 1984) and geothermal systems (Allis and Hunt 1986).…”

Section: Introductionmentioning

confidence: 99%

IMPROVEMENT OF OBSERVATION ACCURACY OF THE LACOSTE‐ROMBERG (MODEL D) GRAVITY METER BY SUPPLEMENTARY INSTALLATION OF ELECTRONIC FEEDBACK¹

Casten

Haußmann

1990

Geophysical Prospecting

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Recent years have seen an increasing need for high‐precision gravity meters. A widely used and the most accurate one is the LaCoste‐Romberg, model D (LCR‐D) meter, equipped with electronic readout. According to the manual the reading accuracy is 5 μGal. A way of reducing most of the instrumental factors limiting the accuracy is the use of an electronic feedback system. We have fitted the LCR‐D 34 with a Schnüll‐Röder‐Wenzel, model D (SRW‐D) feedback. After installation the readout voltage was calibrated, the instrumental behaviour tested, and the accuracy of the system determined. By repeat readings in the laboratory without moving the meter, the standard deviation for a single reading is better than 4 μGal in normal mode and better than 1 μGal in feedback mode. The accuracy of gravity differences ‐ this is usually observed in field practice ‐ is the mean value of the repeat errors of several sets of differences observed in a short time to avoid any corrections. This accuracy is better than 9 μGal in normal mode and better than 5 μGal in feedback mode. With this, the accuracy of a single reading becomes more than 6 μGal and more than 3 μGal, respectively. As the described improvement of accuracy was found to be not as good as expected, additional improvements should centre on the use of electronic levels instead of the standard liquid ones.

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RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS¹

Cited by 14 publications

References 9 publications

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

INDUCED GRAVITY ANOMALIES AND ROCK‐BURST RISK IN COAL MINES: A CASE HISTORY¹

IMPROVEMENT OF OBSERVATION ACCURACY OF THE LACOSTE‐ROMBERG (MODEL D) GRAVITY METER BY SUPPLEMENTARY INSTALLATION OF ELECTRONIC FEEDBACK¹

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RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS1

Cited by 14 publications

References 9 publications

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

Towards the measurement of zero vertical gradient of gravity on the Earth’s surface

INDUCED GRAVITY ANOMALIES AND ROCK‐BURST RISK IN COAL MINES: A CASE HISTORY1

IMPROVEMENT OF OBSERVATION ACCURACY OF THE LACOSTE‐ROMBERG (MODEL D) GRAVITY METER BY SUPPLEMENTARY INSTALLATION OF ELECTRONIC FEEDBACK1

Contact Info

Product

Resources

About

RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS¹

INDUCED GRAVITY ANOMALIES AND ROCK‐BURST RISK IN COAL MINES: A CASE HISTORY¹

IMPROVEMENT OF OBSERVATION ACCURACY OF THE LACOSTE‐ROMBERG (MODEL D) GRAVITY METER BY SUPPLEMENTARY INSTALLATION OF ELECTRONIC FEEDBACK¹