Use of Correlation Fractal Dimension signatures for understanding the Overlying Strata Dynamics in Longwall Coal Mines

Mondal, Debjeet; Roy, Prasanta; Behera, Prasanta Kumar

doi:10.1016/j.ijrmms.2016.11.019

Cited by 42 publications

(14 citation statements)

References 12 publications

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“…The correlation exponent γ is computed by applying scaling laws where the Hurst exponent H ≈ α = 1 − γ /2 is obtained, and for H > 0.5 the system is considered long term correlated, H = 0.5 it is white noise, H < 0.5 it is long term anti-correlated while H > 1 it is a non-stationary local mean [40], [46]- [49]. Accordingly, this power-law decay of values can best be applied using the concept of self-similarity (self-affinity) [39] Self-affine/similar systems are also called fractals [50]- [52]. The concept was introduced by Mandelbrot and has been broadly applied in different disciplines [53].…”

Section: Introductionmentioning

confidence: 99%

Long Range Correlation in Vegetation Over West Africa From 1982 to 2011

et al. 2019

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Satellite-derived Normalized Difference Vegetation index (NDVI) data records offer important sources for long term correlation modelling over West Africa. In this study, we assessed long range correlations in half monthly NDVI records over West Africa from 1982 to 2011 using GIMMS NDVI. In our analysis, we assessed (a) the annual and seasonal trends obtained using Ordinary Linear Regression, (b) the detrended lag-1-autocorrelation C(1), (c) the Detrended Fluctuation Analysis (DFA) scaling Hurst exponent h and (d) the Multifractal (MF) characteristics of NDVI. Results show that there exist some patterns or trends in the records that persist over time. The value of C(1) for NDVI was obtained as 0.989 is significant at 95% confidence interval. Consequently, the scaling h values of the Hurst DFA showed that about 37.4, 20.5, 41.7 and 0.5% of the vegetated areas are anti-correlated (h < 0.5), un-correlated (h = 0.5), correlated (0.5 < h < 1) and uncorrelated random walk (h = 1), respectively. The trend analysis from Ordinary Least square Regression (OLR) shows that about 54.3, 0.1 and 45.6% of the vegetated areas are positively, uncorrelated and negatively correlated, respectively. Our findings revealed that the DFA method performed better than OLR and the findings could be useful in identifying areas with improved and degraded vegetation, which cannot be properly captured by the OLR method. Accordingly, the comparison of the MF-DFA results of original data to those of shuffled and surrogate series indicated that the multifractal nature of considered time-series is both from PDF and long-range correlations but arguably, MF due to long range correlation dominates over West Africa. The research is therefore helpful in the formulating crop and environmental management policies that may be used to improve ecosystem management using a long term plan (inter-annual) or short term (inter-seasonal) planning. INDEX TERMS Long range correlation, multifractality, NOAA AVHRR, NDVI, ecological zones, West Africa.

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Section: Introductionmentioning

confidence: 99%

Long Range Correlation in Vegetation Over West Africa From 1982 to 2011

et al. 2019

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“…Fractal dimension calculated based on the distribution of AE counts reveal the overall features of AE counts distribution, energy release, and specimen failure. Correlations between fractal dimension and energy dissipation during the coal mining process is broadly used in the characterization and dynamic failure prediction [12,37,48]. us, the fractal dimension also provides the feasibility in expanding the laboratory experimental results to the fieldwork, if the correlation of the fractal dimension and energy dissipation between the two scales are established.…”

Section: Scale Effect On the Ae Featuresmentioning

confidence: 99%

Scale Effect on the Anisotropy of Acoustic Emission in Coal

Song

Zhao

Jiang

et al. 2018

Shock and Vibration

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Acoustic emission (AE) in coal is anisotropic. In this paper, we investigate the microstructure-related scale effect on the anisotropic AE feature in coal at unconfined loading process. A series of coal specimens were processed with diameters of 25 mm, 38 mm, 50 mm, and 75 mm (height to diameter ratio of 2) and anisotropic angles of 0°, 15°, 30°, 45°, 60°, and 90°. The cumulative AE counts and energy dissipation increase with the specimen size, while the energy dissipation per AE count behaves in the opposite way. This may result from the increasing amount of both preexisting discontinuities and cracks (volume/number) needed for specimen failure and the lower energy dissipation AE counts generated by them. The effect of microstructures on the anisotropies of AE weakens with the increasing specimen size. The TRFD and its anisotropy reduce as the specimen size increases, and the reduction of fractal dimension is most pronounced at the anisotropic angle of 45°. The correlation between TRFD and cumulative AE energy in the specimens with different sizes are separately consistent with the negative exponential equation proposed by Xie and Pariseau. With the specimen size gain, the reduction of the TRFD weakens with the increasing amount of cumulative absolute AE energy.

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“…High strength of direct roof mediumthick strata, large thickness, and low strata lead to high roof pressure [15,16]. On the other hand, the instability of the overlying structure usually produces large vibration energy [17][18][19], which produces high dynamic and static load [20][21][22] to the working face and easily induces coal and rock dynamic disasters.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Coal Bump among Mine Group under the Control of Large Geological Body: A Case Study of Yima Mining Area, China

Zhao

et al. 2021

Advances in Civil Engineering

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Coal bump often occurs in coal mining among many working faces in mine group under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces under the conditions of large fault and huge thick overburden conglomerate, this paper regards Yima mining area as a practical engineering background and theoretically analyzes the mechanical behavior of overlying rock in the spatial structure. Then, the deep-ground and whole-space measurement is carried out in the 13230 working face of Gengcun mine and 21121 working face of Qianqiu mine. The results show that the basic structural unit in Yima mining area is composed of two goafs, middle coal pillar, and overlying conglomerate. Under the condition of nonsynchronous mining in adjacent working faces, there is a comovement effect similar to lever’s “prying” phenomenon in thick conglomerate beam—the conglomerate strata above larger goaf side induce an overall uplift movement of the corresponding strata above smaller goaf side, and uplift length of the conglomerate strata is related to the mining length, coal pillar width, caving angle, and coal-conglomerate distance. The results of surface subsidence, microseism, and stress in the two working faces verify the conglomerate’s phenomenon of comovement effect and disturbance range and further explain the role of active movement of F16 fault and overall causes of huge thick conglomerate on the coal bump. The vertical stress of the 13230 face is relatively low at the beginning, and high horizontal stress by fault activation causes typical bump accident with the horizontal sliding of coal body. With the increasing development of 13230 face, the intensity and frequency of coal bump in horizontal direction decrease obviously, but with high proportion in vertical direction. The results provide a theoretical basis for the study on the mechanism of coal bump between two adjacent working faces under the conditions of huge thick conglomerate and large thrust fault.

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Use of Correlation Fractal Dimension signatures for understanding the Overlying Strata Dynamics in Longwall Coal Mines

Cited by 42 publications

References 12 publications

Long Range Correlation in Vegetation Over West Africa From 1982 to 2011

Long Range Correlation in Vegetation Over West Africa From 1982 to 2011

Scale Effect on the Anisotropy of Acoustic Emission in Coal

Mechanism of Coal Bump among Mine Group under the Control of Large Geological Body: A Case Study of Yima Mining Area, China

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