Origin of the Anomalies of Gravity and Its Vertical Gradient Over Cavities in Brittle Rock*

Fajklewicz, Zbigniew

doi:10.1111/j.1365-2478.1986.tb00526.x

Cited by 14 publications

(7 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When a causative 2D body has limited and similar horizontal and vertical dimensions, the centre of its mass coincides with the singular point of gravity potential and its derivatives (Golizdra 1963;Fajklewicz 1976Fajklewicz , 1983Fajklewicz , 1986). The singular points of a function of the vertical component of gravity attraction of bodies are determined by analytic continuation of the gravity anomalies.…”

Section: Data Inversionmentioning

confidence: 99%

See 1 more Smart Citation

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

Casten

Fajklewicz

1993

Geophysical Prospecting

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Data Inversionmentioning

confidence: 99%

“…For automated anomaly interpretation utilizing a computer, special software has been developed at the Institute of Geophysics, Krakow. Examples of successful applications have been given by Fajklewicz and Madej (1982) and Fajklewicz (1986).…”

Section: Data Inversionmentioning

confidence: 99%

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

Casten

Fajklewicz

1993

Geophysical Prospecting

Self Cite

View full text Add to dashboard Cite

show abstract

“…Consequently, they influence the gravity measurements at the surface. Microgravity applications to detect cavities, whether natural (collapse, karst) or human made (galleries and shafts of an old mine, urban network, buried subterrains) can be found in the literature (Arzi ; Butler ; Fajklewicz ; Hinze ; Wenjin and Jiajian ; Comacho et al ; Yule et al ; Beres et al ).…”

Section: Introductionmentioning

confidence: 99%

Depth estimation of cavities from microgravity data using a new approach: the local linear model tree (LOLIMOT)

Hajian

Zomorrodian

Styles

et al. 2011

Near Surface Geophysics

View full text Add to dashboard Cite

In this paper an attempt is made to estimate depth and shape parameters of subsurface cavities from microgravity data through a new soft computing approach: the locally linear model tree, known as the LOLIMOT algorithm. This method is based on locally linear neuro‐fuzzy modelling, which has recently played a successful role in various applications over non‐linear system identification. A multiple‐LOLIMOT neuro‐fuzzy model was trained separately for each of the three most common shapes of subsurface cavities: sphere, vertical cylinder and horizontal cylinder. The method was then tested for each of the cavity shapes with synthetic data. The model's suitability for application to real cases was analysed by adding random Gaussian noise to the data to simulate several levels of uncertainty and the results of LOLIMOT were compared to both multi‐layer perceptron neural network and least‐squares minimization methods. The results showed that the LOLIMOT algorithm is more robust to noise and is also more precise than either the multi‐layer perceptron or least‐squares minimization method. Furthermore, the method was tested with microgravity data over a selected site located in a major container terminal at Freeport, Grand Bahamas, to estimate cavity depth and was compared to the results achieved by least‐squares minimization and multi‐layer perceptron methods. The proposed method can estimate cavity parameters more accurately than the least‐squares minimization and multi‐layer perceptron methods.

show abstract

“…Safety problems at the surface may arise from near-surface cavities like caverns or shallow abandoned mine workings. Both the microgravimetric method and the observation of vertical gradients of the gravity field provided essential information for the detection of these cavities (Sommer 1983;Fajklewicz 1986). Dresen et al (1981) improved the instrumentation techniques in vertical tower gradient observations.…”

Section: Introductionmentioning

confidence: 99%

RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS¹

Casten

Gram

1989

Geophysical Prospecting

View full text Add to dashboard Cite

Underground gravity observations in deep coal mines using the conventional gravity meters Worden (type Master) and LaCoste‐Romberg (model D), both of which have been adapted to the fire damp regulations, can be accurate to ± 10 and ± 3 μgal, respectively. For underground determination of the vertical gradient of gravity the LaCoste‐Romberg meter is used together with a specially designed measuring tower. Using this euipment an accuracy in tower gradient observations of ± 30 E was obtained. To apply the equipment to precision gravity observations in underground situations an additional correction, i.e. a gallery correction, is needed. High accuracy in correction is achieved by a new method of three‐dimensional modelling. The gravity effect is computed for bodies with a surface approximated by triangular elements, which are generated from corner points of the body. The combination of gallery correction with tower gradient data leads to a new method for in situ density determination. It offers the possibility of horizontal instead of vertical density profiling. To demonstrate the effectiveness of the developments in underground observations the localization of a pump room is presented. Microgravity and tower gradient observations were carried out to detect the cavity. The horizontal gradient was also calculated to give a more reliable location.

show abstract

Origin of the Anomalies of Gravity and Its Vertical Gradient Over Cavities in Brittle Rock*

Cited by 14 publications

References 6 publications

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

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

Depth estimation of cavities from microgravity data using a new approach: the local linear model tree (LOLIMOT)

RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS¹

Contact Info

Product

Resources

About

Origin of the Anomalies of Gravity and Its Vertical Gradient Over Cavities in Brittle Rock*

Cited by 14 publications

References 6 publications

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

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

Depth estimation of cavities from microgravity data using a new approach: the local linear model tree (LOLIMOT)

RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS1

Contact Info

Product

Resources

About

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

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

RECENT DEVELOPMENTS IN UNDERGROUND GRAVITY SURVEYS¹