scholarly journals Mechanism and Integrated Control of “Rib Spalling: Roof Collapse—Support Instability” Hazard Chains in Steeply Dipping Soft Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Shuai Liu ◽  
Ke Yang ◽  
Chunan Tang
Keyword(s):  
Underground Mining ◽  
Integrated Control ◽  
Three Dimensional ◽  
Friction Angle ◽  
Coal Seams ◽  
Limit States ◽  
Roof Collapse ◽  
Soft Coal ◽  
Wall Element ◽  
Coal Wall

The hazard chain of rib spalling, roof collapse, and support instability occurring in steeply dipping coal seams (SDCSs) significantly threatens the safety and productivity of underground mining. A three-dimensional coal wall model was established considering the damage to the coal wall from the abutment pressure based on the new concept of the main control weak surface (MCWS) defined by the authors. Then, a support mechanical model under the conditions of a dynamic load induced by a sliding roof was constructed. Integrated control measurements based on the models above were developed and taken for the dangerous area of hazard chains in working faces. The results indicated that the dimensions of rib spalling were dominated by the shape, dimensions, and friction angle of the coal wall element. In detail, the order of the importance of the element failure factors, based on their sensitivities, was the roof load (6.33), the dip of the panel (−5.03), the friction angle of the coal (−3.24), the cohesion of the coal (−3.02), and the sidewall protecting force (−0.087). Additionally, the order of importance of the frictional sliding factors of the slip body was the MCWS cohesion (−0.293), roof load (0.213), and MCWS friction angle (−0.079). Equations for the threshold forces between supports under the support dumping and sliding limit states were obtained; the knowledge of these forces ensured support stability under a sliding roof. The support work resistance varied synchronously in different parts of the working face and remained within 2200–4000 kN, indicating that the proposed models and control measurements considered instrumental in hazard chain control in SDCSs were reliable.

ANALYSIS OF CONTROLLED COAL DISCHARGE AT MINING OF THICK FLAT COAL SEAMS USING SELF-CAVING TECHNOLOGY

2021 ◽  
Vol 4 (1) ◽  
pp. 389-399
Author(s):  
S.V. Klishin ◽  
Keyword(s):  
Numerical Analysis ◽  
Discrete Element Method ◽  
Underground Mining ◽  
Three Dimensional ◽  
Discrete Element ◽  
Flow Patterns ◽  
Coal Extraction ◽  
Coal Seams ◽  
Element Method

By the Discrete Element Method in a three-dimensional formulation, a numerical analysis of the areal coal discharge during the underground mining of thick flat coal seams using self-caving technology has been carried out. The kinematic flow patterns of mined rock depending on the number and location of the outlet openings are given, the zones of their mu-tual influence are determined. The change of coal extraction indicators depending on the num-ber of outlets and the distance between them are demonstrated.

Substantiation of safe underground mining in series of coal seams under hydraulic fill

2018 ◽  
Vol 8 ◽  
pp. 217-226
Author(s):  
Yu.I. Kutepov ◽  
◽  
A.S. Mironov ◽  
Yu.Yu. Kutepov ◽  
M.V. Sablin ◽  
...  
Keyword(s):  
Underground Mining ◽  
Coal Seams ◽  
Hydraulic Fill ◽  
In Series

Optimizing Shearer Web Width in Underground Mining of Gently Dipping Methane-Bearing Coal Seams

2019 ◽  
Vol 55 (6) ◽  
pp. 938-945
Author(s):  
A. A. Ordin ◽  
A. M. Timoshenko ◽  
D. V. Botvenko
Keyword(s):  
Underground Mining ◽  
Coal Seams

Inelastic Limit States Design Part II: Three‐Dimensional Frame Study

1992 ◽  
Vol 118 (9) ◽  
pp. 2550-2568 ◽  
Author(s):  
Ronald D. Ziemian ◽  
William McGuire ◽  
Gregory G. Dierlein
Keyword(s):  
Three Dimensional ◽  
Limit States

scholarly journals Failure Mechanisms and the Control of a Longwall Face with a Large Mining Height within a Shallow-Buried Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Haijun Wang ◽  
Yingjie Liu ◽  
Yuesong Tang ◽  
Hao Gong ◽  
Guoliang Xu
Keyword(s):  
Tensile Stress ◽  
Coal Mine ◽  
Horizontal Displacement ◽  
Longwall Face ◽  
Mining Equipment ◽  
Coal Seams ◽  
Increasing Trend ◽  
Support Force ◽  
Coal Wall ◽  
Mining Height

The capabilities of mining equipment and technology in China have been improving rapidly in recent years. Correspondingly, in the western part of the country, the mining heights of longwall faces in shallow-buried coal seams have shown an increasing trend, resulting in enhanced mining efficiency. However, the problems associated with the possible failure of the coal wall then increase and remain a serious difficulty, restricting safe and efficient mining operations. In the present study, the 12401 longwall face of the Shangwan Coal Mine, Inner Mongolia, China, with a mining height of 8.8 m, is taken as an example to study the mechanisms underlying failure phenomena of coal walls and their control methods. Our results show that the failure region inward of the longwall face is small in shallow-buried coal seams, and the damage degree of the exposed coal wall is low. The medium and higher sections of the coal wall display a dynamic failure mode, while the broken coal blocks, given their initial speed, threaten the safety of coal miners. A mechanical model was developed, from which the conditions for tensile failure and structural instability are deduced. Horizontal displacement in the lower part of the coal wall is small, where no tensile stress emerges. On the other hand, in the intermediate and higher parts of the coal wall, horizontal displacement is relatively large. In addition, tensile stress increases first with increasing distance from the floor and then decreases to zero. Experiments using physical models representing different mining heights have been carried out and showed that the horizontal displacement increases from 6 to 12 mm and load-bearing capacity decreases from 20 to 7.9 kN when the coal wall increases in height from 3 to 9 m. Furthermore, failure depth and failure height show an increasing trend. It is therefore proposed that a large initial support force, large maximum support force, large support stiffness, and large support height of a coal wall-protecting guard are required for the improved stability of high coal walls, which operate well in the Shangwan coal mine.

scholarly journals Determination and quality classification of rock mass of the Diatomite mine, Algeria

2021 ◽  
Vol 1 ◽  
pp. 17-24
Author(s):  
Abdessattar LAMAMRA ◽  
◽  
Dmitriy Leonidovich NEGURITSA ◽  
Samir BEDR ◽  
Ariant A. REKA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Underground Mining ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Classification Systems ◽  
Natural Phenomenon ◽  
Underground Structures ◽  
Dilatancy Angle ◽  
Mining Work

Reserch relaevance. Most ground movements are generally due to rock instability, this natural phenomenon poses a risk to humanity. The properties of the rock mass directly influence the type of movement especially in underground structures. Research aim. Our goal is to characterize and classify the rock mass of diatomite from the sig mine using geomechanical classification systems such as the RQD and RMR in order to determine the quality of the rocks in the sig mine Western Algeria from the determination of the physical and mechanical properties. Methodology. In this article, the characterization analysis of the diatomite rock mass of the sig mine was carried out. First, determinations of the physical properties and carried out the triaxial test to determine the mechanical properties (young’s modulus, the friction angle, the dilatancy angle, the cohesion, the poisson’s ratio). Secondly to classify the deposit and give a recommendation to avoid stability problems. Research results. The results from physical and mechanical analyzes, it can be said that the nature of the rock present in the diatomite (underground mine) does not have enough resistance. Conclusion. Our study definitively proves that the rock mass of sig diatomite is of very low quality and it will be very dangerous for the underground mining work of the mine especially in places where the mineralized layer is very deep. And we suggest to replace the mining technique room and pillar currently used in the diatomite mine and put another mining method which includes roof support system to ensure the safety both of the miners and the equipment.

scholarly journals Research on Control of Rib Spalling Disaster in the Three-Soft Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Feng Cui ◽  
Tinghui Zhang ◽  
Xiaoqiang Cheng
Keyword(s):  
Coal Seam ◽  
Field Experiments ◽  
Simulation Experiment ◽  
Current Status ◽  
Soft Coal ◽  
Grouting Pressure ◽  
Working Face ◽  
Coal Wall ◽  
Soft Coal Seam ◽  
Seam Mining

Rib spalling disaster at the coal mining faces severely restricted the safe and efficient output of coal resources. In order to solve this problem, based on the analysis of the current status of rib spalling in the three-soft coal seam 1508 Working Face of Heyang Coal Mine, a mechanical model of sliding-type rib spalling was established and the main influencing factors that affect rib spalling are given. The mechanism of grouting technology to prevent and control rib spalling has been theoretically analyzed. A similarity simulation experiment is used to analyze the change law of roof stress under the condition of three-soft coal seam mining. The optimal grouting pressure is determined by a numerical simulation experiment. And, silicate-modified polymer grouting reinforcement materials (SMPGMs) are used in field experiments. After twice grouting operations in the 1508 Working Face, the coal wall was changed from the original soft and extremely easy rib spalling to a straight coal wall and the amount of rib spalling has been reduced by 57.45% and 48.43, respectively. And, the mining height has increased by 0.16 m and 0.23 m, respectively. The experimental results show that the rib spalling disaster of the three-soft coal seam has been effectively controlled.

scholarly journals A numerical finite element study on connections of SFRC offshore wind towers with prestressed CFRP reinforcement and steel connectors

2020 ◽  
Vol 5 ◽  
pp. 101-113
Author(s):  
Chandan Gowda ◽  
Fabio P. Figueiredo ◽  
Joaquim A. O. Barros ◽  
António Ventura-Gouveia
Keyword(s):  
Finite Element ◽  
Friction Angle ◽  
Offshore Wind ◽  
Advanced Materials ◽  
Limit States ◽  
Steel Fibre Reinforced Concrete ◽  
Shear Friction ◽  
Nonlinear Features ◽  
Parametric Analyses ◽  
Material Nonlinear

The growing need for sustainable production of electricity highlights the importance and the necessity of having higher number and more effective offshore wind towers. The rapid growth of offshore wind towers is estimated to produce 4% of electricity demands in Europe by the end of 2020. The research described in this paper is part of a project dedicated for the development of innovative structural system using advanced materials for lightweight and durable offshore towers. Specifically, it discusses the nonlinear finite element modelling of the connection between representative prefabricated rings of offshore wind tower made by steel fibre reinforced concrete (SFRC), and prestressed by a hybrid system of carbon fibre reinforced polymers (CFRP) bars and steel strands. This connection is assured by post-tension high steel strength cables and concrete-concrete shear friction width an idealized geometric configuration of the faces in contact. The model takes into account the loads from the rotor, wind and water currents, by considering the critical loading conditions for the safety verifications of serviceability and ultimate limit states. The material nonlinear analyses are carried out with FEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The parametric analyses involve the influence on the relevant results of the SFRC fracture parameters, pre-stress level of the reinforcements, shape of interlock mechanism, friction angle and interface cohesion.

Massive Hydraulic Fracturing to Control Gas Outbursts in Soft Coal Seams

2022 ◽  
Author(s):  
Shuaifeng Lyu ◽  
Shengwei Wang ◽  
Junyang Li ◽  
Xiaojun Chen ◽  
Lichao Chen ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Seams ◽  
Soft Coal
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