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Fundamentals of modern ground control management in Australian underground coal mines

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International Journal of Mining Science and Technology 2020年第5期30卷 573-582页

作者： Jason Emery Ismet Canbulat chengguo zhang School of Minerals and Energy Resources Engineering University of New South WalesSydneyNSW 2052Australia

Underground coal mining is inherently hazardous,with uncontrolled ground failure regarded as one of only several critical risks for multiple fatality ***,implementation and management of overarching systems and procedures for maintaining strata control is an important step to mitigating the impact of ground failure hazards at a mine site operational *** paper summarised the typical pro-active ground control management system(PGCMS)implemented in various Australian underground coal *** produces approximately 100 million tonnes a year of metallurgical and thermal coal from approximately 30 of the world’s safest longwall mines operating in New South Wales and *** increased longwall productivity required to achieve both high levels of safety and profitability,places significant emphasis on the reliability of pro-active ground control management for longwall mining *** depths,adverse geological conditions,elevated variable stress regimes and weaker ground conditions,coupled with an industry wide need for increased development rates continue to make ground control management *** control management is not only about ground support and pillar design though but also a structured process that requires a coordinated effort from all levels of the workforce to both minimise the occurrence of adverse geotechnical events and mitigate the potential risks when they do *** PGCMS presented in this paper is proven to provide both a safer and more productive mine environment through minimisation of unplanned *** critical elements of the method are presented in detail and demonstrate the utility and value of a ground control management system that has potential for implementation in underground coal mining globally.

关键词： Strata control Ground control Management Longwall Safety Risk

A semi-quantitative coal burst risk classification system

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International Journal of Mining Science and Technology 2018年第5期28卷 721-727页

作者： Onur Vardar chengguo zhang Ismet Canbulat Bruce Hebblewhite School of Minerals and Energy Resources Engineering University of New South Wales

Safety is the highest priority in the mining industry as underground mining in particular poses high safety risks to its workers. In underground coal mines, coal bursts are one of the most catastrophic hazards, which involves sudden and violent dynamic coal mass failure with rapid ejection of the broken material into the mine workings. Despite decades of research, the contributing mechanisms of coal bursts are still not completely understood. Hence, it remains challenging to forecast coal bursts and quantify their likelihood of occurrence. However, a range of geological and geotechnical factors are associated with coal bursts and can increase the coal burst proneness. This paper introduces a semi-quantitative coal burst risk classification system, namely, BurstRisk. Based on back-analysis of case histories from Australia, China and the United States, BurstRisk classifies the coal burst risk into three categories:low, medium and high risk. In addition, it allows mining engineers to modify the weighting of the selected factors based on specific conditions. The risk classification charts introduced are for both longwall retreat and development sections of long-wall mining operations. This paper also provides a set of risk management strategies and control measures for effective coal burst mitigation.

关键词： Underground coal mining Coal burst Rockburst Risk management Safety Semi-quantitative

Microcrack fracturing of coal specimens under quasi-static combined compression-shear loading

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第5期12卷 1014-1026页

作者： Qingyuan He Yingchun Li Danqi Li chengguo zhang State Key Laboratory of Coal Resources and Safe Mining School of MinesChina University of Mining and TechnologyXuzhou221116China School of Minerals and Energy Resources Engineering University of New South WalesSydney2052Australia State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian116024China Department of Civil Engineering Monash UniversityClaytonMelbourneVIC3800Australia

Coal pillars are usually loaded under combined compression-shear stresses at underground coal *** long-term stability is critical to the utilization of underground structures,such as underground reservoirs at coal *** this study,a modified rock property testing system was used to explore the mechanical properties of coal specimens under quasi-static combined compression-shear loading *** acoustic emission technique was applied to investigating the microcrack fracturing of coal specimens at various inclination *** experimental results show that specimen inclination has remarkable effects on the microcrack initiation,microcrack damage and ultimate failure of the coal *** failure mode of the coal specimen tends to transit from axial splitting to shear failure with increasing specimen inclination,and its peak strength is closely associated with the microcrack damage *** practice,it is recommended to consider coal strength under combined compression-shear loading when using empirical pillar strength formulae so that the effect of pillar inclination can be included.

关键词： Microcrack initiation(CI) Microcrack damage(CD) Microcrack fracturing Acoustic emission Coal properties

Assessment of energy release mechanisms contributing to coal burst

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International Journal of Mining Science and Technology 2017年第1期27卷 43-47页

作者： zhang chengguo Canbulat Ismet Tahmasebinia Faham Hebblewhite Bruce School of Mining Engineering UNSW Sydney 2052Australia

Coal burst is a dynamic release of energy within the rock （or coal） mass leading to high velocity expulsion of the broken/failed material into mine openings. This phenomenon has been recognised as one of the most catastrophic failures associated with the coal mining industry, which can often lead to injuries and fatalities of miners as well as significant production losses. This paper aims to examine the mecha- nisms contributing to coal burst occurrence, with an emphasis on the energy release concept. In this study, a numerical modelling study has been conducted to evaluate the roles and contributions of differ- ence energy components. The energy analysis presented in this paper can help to improve the under- standing of energy release mechanisms esoeciallv under Australian conditions.

关键词： Coal burstCoal burst mechanismsEnergy releaseNumerical modellingMine geomechanics

Statistical analysis of distribution patterns of coal seams in fold zones in Northwest China

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International Journal of Mining Science and Technology 2018年第5期28卷 819-828页

作者： Anye Cao Guangcheng Jing Linming Dou Yun Wu chengguo zhang Key Laboratory of Deep Coal Resource Mining Ministry of Education of China China University of Mining & Technology School of Minerals and Energy Resources Engineering University of New South Wales

The mechanisms for rock bursts occurrences in fold zones are complex, and the redistribution of in-situ stresses is closely related to the complexity of the structures. Analysis of the geomorphology of fold structures and changes of coal thickness can help identify zones prone to rock bursts to improve safety and productivity in coal mines. This study investigated the distribution characteristics of fold structures in coal seams in fold zones in four mines in northwest China. Geometrical characteristics of fold structures in coal seams and changes of coal thickness were analysed, based on comprehensive evaluation indexes,such as the length–width ratio of folds, interlimb angle, ratio P1 of projected width of fold limbs to that of the hinge zone, curvature ratio P2, the maximum curvature and amplitude. The statistical analysis of the four coal mines shows that the length–width ratio of folds changed from 0.78 to 2.03 and the maximum curvature of cross sections of folds was less than 0.04. The curvature ratio of cross section of a fold in the structure was no more than 1.4 and the interlimb angles of cross sections of 89% of folds were larger than 150°. Gentle fold structures were dominant and the specific geological morphologies were domes or basins. The isopleth of coal thickness above the coal mines showed a fluctuation trend similar to the contour line of the floor of coal seams. The coal thickness in an anticline area was smaller than that in the neighboring syncline area. Therefore, the overall variation of coal thickness in the mining areas was likely to have a relation with the direction of the regional principal stress.

关键词： Rock burst Fold structure Distribution pattern Changes of coal thickness Principal stress

Computing the damage and fracture energy in a coal mass based on joint density

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International Journal of Mining Science and Technology 2018年第5期28卷 813-817页

作者： Faham Tahmasebinia chengguo zhang Ismet Canbulat Onur Vardar Serkan Saydam School of Minerals and Energy Resources Engineering University of New South Wales

Coal joints and cleats are geological discontinuities that are the most important factors that affect the mechanical responses of a coal mass under stress. The joint and coal mass interaction and the mode of failure dominate the mechanical behaviour of jointed coal masses, and therefore the stability of coal excavations. The shear or mixed shear/tensile failure changes to tensile failure by increasing the confining pressure, discontinuity length and angle. This paper extends a thermodynamic approach to constitutive modelling of the coal mass by developing local and non-local damage models based on the joint and cleat density and the dip angle. A consistent and rigorous statistical framework is constructed, which incorporates both local and non-local features into the constitutive modelling. This is an important consideration in developing damage constitutive models based on the trajectory of the failure surfaces in a coal *** equation is derived to calculate the fracture energy which is a function of the joint density either in a single direction or crossed conditions.

关键词： Joint density Dissipated energy Coal mass Damage model

Numerical and analytical simulation of the structural behaviour of fully grouted cable bolts under impulsive loading

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International Journal of Mining Science and Technology 2018年第5期28卷 807-811页

作者： Faham Tahmasebinia chengguo zhang Ismet Canbulat Onur Vardar Serkan Saydam School of Minerals and Energy Resources Engineering University of New South Wales

Designing reliable yielding support system to mitigate the effect of the kinetic energy in burst-prone conditions in mining and tunneling excavations is one of the challenges for geotechnical engineers. A combination of the support elements can be used to increase rock strength and minimise the displacement of unstable rock mass. It is important to understand how the support system works to ensure the stability of underground excavations. Cable bolts have been commonly used as an effective underground support system and an element of reinforcement to improve rock stability. Cable bolts are usually considered to be subjected to static loads under relatively low stress environments, however, in burst-prone conditions, they might be subjected to dynamic loads. Cable bolts as well as other support elements are used in burst-prone conditions to absorb the kinetic energy of the removed rock to avoid sudden and violent failures. This paper develops numerical and a novel analytical simulation technique for cable bolts to assess their structural behaviour under static and dynamic loading conditions. The numerical and analytical models are then validated against experimental observations reported in the literature, which demonstrates the reliability of the proposed models.

关键词： Cable bolts Yielding support Coal burst Shear dynamic loading

Numerical modelling of strength and energy release characteristics of pillar-scale coal mass

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第5期11卷 935-943页

作者： Onur Vardar chengguo zhang Ismet Canbulat Bruce Hebblewhite School of Minerals and Energy Resources Engineering.University of New South Wales

Coal burst is a manifestation of rapid energy release,which is considered as one of the most critical operational hazards in underground coal *** study numerically investigates the effects of discontinuities on the strength and energy release characteristics of coal mass samples under uniaxial *** universal distinct element code(UDEC)was used to model pillar-scale coal mass samples that were represented by an assembly of triangular deformable blocks,and pre-existing discontinuities such as bedding planes and cleats were also included in the *** shows that cleat spacing can have a significant impact on compressive strength and energy release,with both strength and energy release(magnitude and rate)reducing as the number of cleats was *** work is one of the first attempts to numerically model and quantify the energy release which occurs during the failure of pillar-scale coal mass samples with varying cleat *** insights from the numerical modelling can help to understand the possible energy release mechanisms and associated coal burst potential in changing coal cleat conditions.

关键词： Coal burst Coal clearing Energy release Distinct element method(DEM) Numerical modelling

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

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Mining Science and Technology 2011年第1期21卷 23-27页

作者： Wang Xufeng zhang Dongsheng Fan Gangwei zhang chengguo School of Mines Chino University of Mining ＆ Technology Xuzhou 221116 China Stote Key Laboratory of Coal Resource and Mine Safety Chino University of Mining ＆ Technology Xuzhou 221008 China

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 *** results show that the intensity of underground pressure is related to its relative position at 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 *** 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 *** subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground *** 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.

关键词： Shallow coal seam Gully slope Back-gully mining Underground pressure