Main geological and mining factors affecting ground cracks induced by underground coal mining in Shanxi Province, China

As one of the largest coal-rich provinces in China,Shanxi has extensive underground coal-mining operations.These operations have caused numerous ground cracks and substantial environmental damage.To study the main geological and mining factors influencing mining-related ground cracks in Shanxi,a detailed investigation was conducted on 13 mining-induced surface cracks in Shanxi.Based on the results,the degrees of damage at the study sites were empirically classified into serious,moderate,and minor,and the influential geological and mining factors(e.g.,proportions of loess and sandstone in the mining depth,ratio of rock thickness to mining thickness,and ground slope)were discussed.According to the analysis results,three factors(proportion of loess,ratio of rock thickness to mining thickness,and ground slope)play a decisive role in ground cracks and can be respectively considered as the critical material,mechanical,and geometric conditions for the occurrence of mining surface disasters.Together,these three factors have a strong influence on the occurrence of serious discontinuous ground deformation.The results can be applied to help prevent and control ground damage caused by coal mining.The findings also provide a direct reference for predicting and eliminating hidden ground hazards in mining areas.

Fuzzy inference system using genetic algorithm and pattern search for predicting roof fall rate in underground coal mines

One of the most dangerous safety hazard in underground coal mines is roof falls during retreat mining.Roof falls may cause life-threatening and non-fatal injuries to miners and impede mining and transportation operations.As a result,a reliable roof fall prediction model is essential to tackle such challenges.Different parameters that substantially impact roof falls are ill-defined and intangible,making this an uncertain and challenging research issue.The National Institute for Occupational Safety and Health assembled a national database of roof performance from 37 coal mines to explore the factors contributing to roof falls.Data acquired for 37 mines is limited due to several restrictions,which increased the likelihood of incompleteness.Fuzzy logic is a technique for coping with ambiguity,incompleteness,and uncertainty.Therefore,In this paper,the fuzzy inference method is presented,which employs a genetic algorithm to create fuzzy rules based on 109 records of roof fall data and pattern search to refine the membership functions of parameters.The performance of the deployed model is evaluated using statistical measures such as the Root-Mean-Square Error,Mean-Absolute-Error,and coefficient of determination(R_(2)).Based on these criteria,the suggested model outperforms the existing models to precisely predict roof fall rates using fewer fuzzy rules.

Underground pressure characteristics analysis in back-gully mining of shallow coal seam under a bedrock gully slope

We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.

The influence of mining factors on seismic activity during longwall mining of a coal seam

In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was conducted.Two longwall panels were mined in analogous geological conditions and based on the same mining system and technology.However,there was significant difference with regards to the mining factors,which was reflected in the observed seismic activity.Some tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors,e.g.the frequency-energy distribution,the frequency-magnitude distribution,the 2 D distribution of released seismic energy,the relationship between released seismic energy and the volume of mined coal,the Benioff strain release,and the Gutenberg-Richter(GR)b coefficient distribution(b is the proportion between high and low energy tremors).Concerning the Benioff strain release,a new solution,based on the slope of a fitted line in a moving time window,is proposed.

A review of the geomechanics aspects of a double fatality coal burst at Austar Colliery in NSW,Australia in April 2014

A coal burst occurred on 15 April, 2014 at the Austar Coal Mine, located west of Newcastle, NSW,Australia. The burst resulted in fatal injuries to two men working as part of the mining crew at the development face. At the time, a continuous miner was being used to mine a longwall development gate road through heavily structured coal, at a depth of approximately 550 m. A number of pre-cursor bumps had occurred on previous shifts, emanating from the coal ribs of the roadway, in proximity to the coal face.This paper reviews the geological, geotechnical and mining conditions and circumstances leading up to the coal burst event; and presents and discusses the available evidence and possible interpretations relating to the geomechanical behaviour mechanisms that may have been critical factors in this incident. The paper also discusses some key technical and operational considerations of ground support systems and mining practices and strategies needed for operating in such conditions in the future.

Assessment of pot-hole subsidence risk for Indian coal mines

Ground subsidence induced by extraction of coal seam belowground brings about changes in surface environment leading to trough and pot-hole subsidence.Pot-hole subsidence is extremely hazardous and does not give any prior indication before its occurrence.In India,several pot-holes have occurred in the coal mines of South Eastern Coalfields Limited triggering the need for in-depth studies.In line with the requirement,literature review and field investigations were conducted to develop an in-depth understanding of various parameters influencing the occurrence of pot-holes.The critical parameters identified were rock to soil ratio,depth to height of extraction ratio,brittleness index of rock and rock density.Risk assessment of pot-hole subsidence has been done by developing an empirical rating approach named as pot-hole subsidence rating(PHSR),involving the critical parameters with suitable corrections for certain structural and mining conditions to obtain corrected PHSR(CPHSR).CPHSR was then applied for all the 34pot-holes studied and it was found that all the pot-holes fall under Class I and Class II category of risk representing a very high to high risk class.An effort was made for the estimation of pot-hole depth utilizing the developed CPHSR in both the development and depillaring cases.The developed approach was found to yield consistent results in pot-hole depth prediction.

Research of CAN Bus in the Coal Mine Field Data Transmission based on Reliability

Under the current situation, China＇ s rapid economic development, various new science, emerge in an endless stream of new technology, under the environment of coal mine industry, seize the opportunity, by virtue of its original advantages, coupled with technology introduction and innovation consciousness of the play, ushered in a new period of development, into the modern coal mining era. CAN bus technology is a new technology which has the typical data transmission in coal mining, the introduction of a certain degree of CAN bus technology, not only improve the efficiency of data transmission, at the same time, in terms of reliability and greatly enhance. In this paper, to a certain extent on the introduction of the CAN bus technology, and on this basis, based on the CAN bus in the coal mine field data transmission reliability research and analysis

Applying a statistical method to streamflow reduction caused by underground mining for coal in the Kuye River basin

Streamflow in the Kuye River basin has been sharply reduced by the effects of climate change and human activities.Since 1997,the intensification of coal mining has resulted in substantial reductions to streamflow alongside an ever-increasing demand for water.In this study,we present a derived statistical method,incorporating the Mann-Kendall and Pettitt method(MK-P) and the Soil and Water Assessment Tool(SWAT),and apply it to estimating the streamflow reductions caused by underground mining for coal in the Kuye River basin.The results show that underground mining is an important cause of the streamflow reductions observed since1997,being responsible for reductions of 21.15 mm/yr(~56%of the total) during 1997-2009.The results of the SWAT simulation were assessed by several performance criteria:Nash-Suttcliffe Efficiency(Nse),correlation coefficient(R^2),relative error(RE),P-factor and Pv-factor.The close match between the simulations and observed data supports the reasonability of our findings.We suggest that engineering strategies be adopted to limit streamflow loss into goafs via fractured zones in the coalfield.

Detecting Surface Subsidence in Coal Mining Area Based on DInSAR Technique

Coal is the primary energy resource in China. Thousands of underground coal mines are operating in China and cause severe land subsidence, leading to many environmental and engineering problems. Huainan （淮南） coal mine is the largest coal mining area in East China. Surface subsidence associated with Huainan coal mining activities has been monitoring by DInSAR （differential synthetic aperture radar） techniques in this study. Four ASAR （advanced SAR） pairs from 2009 to 2010 are selected to perform 2-pass DInSAR processing with spatial and temporal baselines suitable for subsidence monitoring. The subsidence maps generated from these pairs show that the extension of subsidence is consistent with the field observation. Quantitative measurements indicated that the magnitudes of subsidence are increased with the development of underground coal mining exploitation. This study demonstrates that DInSAR technique is effective for surface subsidence monitoring in coal mining area. Limitations and recommendations both in the adopted method and auxiliary data are also discussed.