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Stability and control of room mining coal pillars-taking room mining coal pillars of solid backfill recovery as an example

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Journal of Central South University 2017年第5期24卷 1121-1132页

作者： ZHANG Ji-xiong HUANG Peng ZHANG Qiang LI Meng CHEN Zhi-wei School of Mines China University of Mining&TechnologyXuzhou 221116China The State Key Laboratory for Geo Mechanics and Deep Underground Engineering China University of Mining&TechnologyXuzhou 221116China

The stability of room mining coal pillars during their secondary mining for recovering coal was analyzed. An analysis was performed for the damage and instability mechanism of coal pillars recovered by the caving mining method. During the damage progression of a single room coal pillar, the shape of the stress distribution in the pillar transformed from the initial stable saddle shape to the final arch-shaped distribution of critical instability. By combining the shapes of stress distribution in the coal pillars with the ultimate strength theory, the safe-stress value of coal pillar was obtained as 11.8 MPa. The mechanism of instability of coal pillar groups recovered by the caving mining method was explained by the domino effect. Since the room coal pillars mined and recovered by the traditional caving mining method were significantly influenced by the secondary mining during recovery, the coal pillars would go through a chain-type instability failure. Because of this limitation, the method of solid backfilling was proposed for mining and recovering room coal pillars, thus changing the transfer mechanism of stress caused by the secondary mining(recovery) of coal pillars. The mechanical model of the stope in the case of backfilling and recovering room coal pillars was built. The peak stress values inside coal pillars varied with the variance of backfilling ratio when the working face was advanced by 150 m. Furthermore, when the critical backfilling ratio was 80.6%, the instability failure of coal pillars would not occur during the solid backfill mining process. By taking Bandingliang Coal Mine as an example, the coal pillars' stability of stope under this backfilling ratio was studied, and a project scheme was designed.

关键词： room mining stability of coal pillars coal mining of solid backfill ultimate strength instability failure

On the Three Important "pillars" in the Planning of Modern City

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China City Planning Review 1991年第3期8卷 3-10页

作者： Zou Dici China Academy of Urban Planning and Design

Ⅰ Talking about the planning of"modern" city, one may ask when the con-cept of "modern" started and what charac-teristics it has. In fact, one can only havesome blurred understanding of this

关键词： pillars On the Three Important in the Planning of Modern City

Numerical analyses of pillar behavior with variation in yield criterion,dilatancy, rock heterogeneity and length to width ratio

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 46-60页

作者： Sankhaneel Sinha Gabriel Walton Colorado School of Mines

With recent advances in numerical modeling, design of underground structures increasingly relies on numerical modeling-based analysis approaches. While modeling tools like the discrete element method(DEM) and the combined finite-discrete element method(FDEM) are useful for investigating small-scale damage processes, continuum models remain the primary practical tool for most field-scale *** results obtained from such models are significantly dependent on the selection of an appropriate yield criterion and dilation angle. Towards improving its capabilities in handling mining-related problems, the authors have previously developed a new yield criterion(called progressive S-shaped criterion). The focus of the current study is to demonstrate its use in modeling rock pillars through a comparative analysis against four other yield criteria. In addition to the progressive S-shaped criterion,only one out of the four other criteria predicted a trend in strength consistent with an empirical pillar strength database compiled from the literature. Given the closely-knit relationship between yield criteria and dilation angle in controlling the overall damage process, a separate comparison was conducted using a mobilized dilation model, a zero degree dilation angle and a constant non-zero dilation angle. This study also investigates the impact of meso-scale heterogeneity in mechanical properties on the overall model response by assigning probability distributions to the input parameters. The comparisons revealed that an isotropic model using a combination of progressive S-shaped criterion and mobilized dilation angle model is sufficient in capturing the behaviors of rock pillars. Subsequently, the pillar model was used to assess the effect of L/W(length/width) ratio on the peak strength.

关键词： Rock pillars Progressive S-shaped criterion Numerical modeling

Innovation and future of mining rock mechanics

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第1期13卷 1-21页

作者： Manchao He Qi Wang Qunying Wu Key Laboratory for Geo-mechanics and Deep Underground Engineering China University of Mining and TechnologyBeijing100083China Research Institute for Deep Underground Science and Engineering of Beijing China University of Mining and TechnologyBeijing100083China Shanbei Coal Industry Co. Ltd.Shaanxi Shanmei GroupYulin719000China

The 121 mining method of longwall mining first proposed in England has been widely used around the *** method requires excavation of two mining roadways and reservation of one coal pillar to mine one working *** to considerable excavation of roadway,the mining roadway is generally destroyed during coal *** stress concentration in the coal pillar can cause large deformation of surrounding rocks,rockbursts and other disasters,and subsequently a large volume of coal pillar resources will be *** improve the coal recovery rate and reduce excavation of the mining roadway,the 111 mining method of longwall mining was proposed in the former Soviet Union based on the 121 mining *** 111 mining method requires excavation of one mining roadway and setting one filling body to replace the coal pillar while maintaining another mining roadway to mine one working ***,because the stress transfer structure of roadway and working face roof has not changed,the problem of stress concentration in the surrounding rocks of roadway has not been well *** solve the above problems,the conventional concept utilizing high-strength support to resist the mining pressure for the 121 and 111 mining methods should be *** idea is to utilize mining pressure and expansion characteristics of the collapsed rock mass in the goaf to automatically form roadways,avoiding roadway excavation and waste of coal *** on the basic principles of mining rock mechanics,the“equilibrium mining”theory and the“short cantilever beam”mechanical model are *** technologies,such as roof directional presplitting technology,negative Poisson’s ratio(NPR)high-prestress constant-resistance support technology,and gangue blocking support technology,are developed following the“equilibrium mining”***,the 110 and N00 mining methods of an automatically formed roadway(AFR)by roof cutting and pressure releasing without pillars are *** mining metho

关键词： Mining rock mechanics Equilibrium mining theory Short cantilever beam model Automatically formed roadway without pillars Intelligent mining

Simulation of recovery of upper remnant coal pillar while mining the ultra-close lower panel using longwall top coal caving

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International Journal of Mining Science and Technology 2020年第1期30卷 55-61页

作者： Guorui Feng Pengfei Wang College of Mining Engineering Taiyuan University of TechnologyTaiyuan 030024China

With the depletion of easily minable coal seams,less favorable reserves under adverse conditions have to be mined out to meet the market *** to some historical reasons,large amount of remnant coal was left *** such case history occurred with the remnant rectangular stripe coal pillars using partial extraction method at Guandi Mine,Shanxi Province,*** challenge that the coal mine was facing was that there is an ultra-close coal seam right under it with an only 0.8–1.5 m sandstone dirt band in *** simulation study was carried out to investigate the simultaneous recovery of upper remnant coal pillars while mining the ultra-close lower panel using longwall top coal caving(LTCC).The remnant coal pillar was induced to cave in as top coal in LTCC *** modelling shows that the coal pillars are the abutments of the stress arch structure formed within the overburden *** stability of overhanging roof strata highly depends on the stability of the remnant coal *** the gob development(roof strata cave-in)is intermittent with the cave-in of these coal pillars and the sandstone dirt ***3D numerical modelling shows that the multi-seam interaction has a significant influence on mining-induced stress environment for mining of lower *** pattern of the stress evolution on the coal pillars with the advance of the lower working face was *** is demonstrated that the stress relief of a remnant coal pillar enhances the caveability of the pillars and sandstone dirt band below.

关键词： Simulation Remnant coal pillars Ultra-close Dirt band Longwall top coal caving

Direct strain evaluation method for laboratory-based pillar performance

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第4期11卷 860-866页

作者： K.V.Jessu A.J.S.Spearing WA School of Mines Curtin University

Pillar stability is one of important aspects for underground ***,the stability of the pillars is evaluated empirically based on case studies and site-specific rock mass conditions in *** the empirical approach applicability can sometimes be *** numerical-based approaches are potentially more useful as parametric studies can be undertaken and,if calibrated,can be more *** empirical and numerical approaches are dependent on the strength evaluation of the pillars while the strain developing in the pillars is seldom taken into *** this paper,gypsum and sandstone samples were tested in laboratory with different width-to-height ratios (W/H) to adapt the strain evaluation method to the laboratory-based pillars.A correlation was then developed between the strain and the width-to-height ratio for pillar monitoring *** on the results,a flowchart was created to conduct back analysis for the existing pillars to evaluate their stability and design new pillars,considering the strain analysis of the existing pillars with the W/H ratios modelled.

关键词： Failure strain Critical strain pillars Width-to-height ratio Stability

The Supply-Side Structural Reforms——Adapting to and Leading China's New Normal

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Contemporary Social Sciences 2016年第1期1卷 121-129页

作者： Hu Angang Zhou Shaojie Ren Hao the School of Public Policy and Management Tsinghua University the School of China Studies Tsinghua University

The Central Economic Working Conference proposed supplyside structural reforms which can be regarded as major innovations and necessary measures that adapt to and lead the new normal of economic development. The 13^(th) Five Year Plan is a critical period for the transformation of economic development patterns and economic restructuring, so clarifying the theoretical values and practical significances of the supply-side structural reforms, making a clear explanation of the scientific connotations and policy implications of these reforms from a scientific standpoint, and discussing concrete measures to promote the reforms against the background of the economic new normal not only has academic values but also has important practical implications. Viewed from the practical standpoint of China' s new normal and through analyzing the basic national conditions, this article proposes a roadmap for implementing the proposed reforms and points out that only by doing well in the hybrid operation of "addition, subtraction, multiplication and division", based on the framework of the "five policy pillars", an innovative path of the supply-side structural reforms with Chinese characteristics can be paved.

关键词： the supply-side structural reforms economic new normal five policy pillars the hybrid operation of "addition, subtraction, multiplication and division"

Thome H. Fang on Song-Ming Neo-Confucianism

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孔学堂 2016年第1期3卷 108-118页

作者： Yu Bingyi

Thome H. Fang divided Song-Ming Neo-Confucianism into ＂realistic＂＂idealistic,＂ and ＂naturalistic＂ schools and clarified the reason for the differences across the three schools. Song-Ming Neo-Confucianism not only inherits the classical Confucianism reformulated by Confucius, Mencius, and Xunzi but also adds a Buddhist and Daoist flavor to Confucianism. Fang seriously criticized Neo-Confucians for their obstinacy on moral reason and daotong （the orthodox Confucian way）, particularly their parochial and narrow- minded privileging of daotong. However, he also positioned Neo-Confucianism as one of the four intellectual pillars of Chinese philosophy and highly praised its great contributions to Chinese metaphysics. Fang appreciated Neo-Confucians＇ tolerance toward Daoist and Buddhist thought and explored Neo-Confucian philosophy seperately and independently from early Confucianism.

关键词： Four pillars of Chinese philosophy Thome H. Fang Neo-Confucianism

Evaluating the Role of Governance in the Management of Prunus africana (Hook.f.) Kalkman in the Adamawa Region of Cameroon

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Open Journal of Forestry 2022年第4期12卷 408-431页

作者： Steve Nanfack Tassiamba Jean Lagarde Betti Lucie Félicité Temgoua Liliane Rosine Kourogue Armand Wilfried Ndedy Bile Alain Rayane Mpouam Department of Forestry Faculty of Agronomy and Agricultural Sciences University of Dschang Dschang Cameroon Faculty of Science Department of Biology and Physiology of Plant Organisms University of Douala Douala Cameroon

One of the problems at the root of the poor management of forest resources in Cameroon is the lack of good governance. This study aims to evaluate the governance put in place by the government of Cameroon to ensure better management of Prunus africana. It takes a critical look at the three pillars of forest governance in relation to the management of the resource, which are: policy, legal, institutional and regulatory frameworks (1);planning and decision-making process (2);and finally the implementation, enforcement and compliance of regulations (3). The assessment was conducted using the guide recommended by FAO-PROFOR. Individual and focus group interviews were conducted with stakeholders involved in the P. africana management process. The results in the form of assessment scores revealed poor governance in the management of the resource. This is due to non-compliance with pillars 2 and 3 on the planning and decision-making process as well as the implementation and enforcement of regulations through weaknesses in the principles of transparency, accountability, the effectiveness of management measures and stakeholder participation. These are the points on which management strategies should be based for better management of P. africana in the production forests of the Adamawa region.

关键词： Forest Governance Prunus africana Stakeholders pillars Components