scholarly journals Analysis and Application on Controlling Thick Hard Roof Caving with Deep-Hole Position Presplitting Blasting

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Baobao Chen ◽  
Changyou Liu
Keyword(s):  
Large Scale ◽  
Mining Area ◽  
Field Application ◽  
Deep Hole ◽  
Mining Operations ◽  
Hard Roof ◽  
Measurement Analysis ◽  
Mining Safety ◽  
Strata Behavior ◽  
Working Resistance

For the thick hard roof (THR) in Datong mining area, mining operations often led to large-scale hanging-roof and frequent and strong strata behavior, threatening mining safety seriously. Based on the instability mechanism, the fracture model for THR was established, including rock blocks articulation and combined cantilever beam, and the limit initial and periodic intervals of THR were determined to be 36.0 m and 8.0 m, respectively. The study proposed the deep-hole presplitting blasting (DPB) for weakening THR for mitigating strong strata behaviors. Blasting-induced fracture characteristics were calculated, determining the charging coefficient and holes spacing. LS-DYNA was employed for establishing a DPB model to analyze crack evolution under the synergistic action of blasting stress wave and detonation gas and the attenuation characteristics for rock peak particle velocity, verifying the rationality of blasting parameters. Field measurement analysis indicated that the immediate roof induced a timely collapse to fill the goaf and the THR was effectively cut off near the presplitting line. Meanwhile, the working resistance was utilized with safety allowance. The field application showed the DPB on controlled THR caving achieved the significant effect.

scholarly journals A case study of the periodic fracture control of a thick-hard roof based on deep-hole pre-splitting blasting

2021 ◽  
pp. 014459872110362
Author(s):  
Baobao Chen ◽  
Changyou Liu ◽  
Bing Wang
Keyword(s):  
Distinct Element ◽  
Good Control ◽  
Mining Area ◽  
Deep Hole ◽  
Control Effect ◽  
Roof Collapse ◽  
Hard Roof ◽  
Fracture Evolution ◽  
Distinct Element Code ◽  
Working Resistance

A thick-hard roof implies a large hanging-roof and high-frequency dynamic strata behaviour during mining, which may jeopardise personnel safety and equipment. To alleviate these hazards, deep-hole pre-splitting blasting is employed to control periodic fractures in thick-hard roof seams in Datong mining area. Based on loading and instability characteristics, a mechanical model of thick-hard roof periodic collapse is established to investigate the relationships and optimal parameters among the collapse interval, fracturing angle and support working resistance. LS-DYNA was employed to analyse the fracture evolution to determine the optimal charge parameters. The minimum weakening width and average fragmentation of the pre-split roof are obtained. Universal distinct element code simulations were used to determine the thick-hard roof collapse morphology and strata behaviour to confirm the optimal pre-splitting parameters. The deep-hole pre-splitting blasting on-site implementation reduces thick-hard roof collapse intervals, and the supports loading is verified to be safe with sufficient allowance, which show a good control effect on thick-hard roof seams.

scholarly journals Water Preservation and Conservation above Coal Mines Using an Innovative Approach: A Case Study

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2818
Author(s):  
Yujun Xu ◽  
Liqiang Ma ◽  
Yihe Yu
Keyword(s):  
Coal Mining ◽  
Water Conservation ◽  
Large Scale ◽  
Influencing Factor ◽  
Mining Area ◽  
Mining Operations ◽  
Narrow Strip ◽  
Geological Conditions ◽  
The Impact

To better protect the ecological environment during large scale underground coal mining operations in the northwest of China, the authors have proposed a water-conservation coal mining (WCCM) method. This case study demonstrated the successful application of WCCM in the Yu-Shen mining area. Firstly, by using the analytic hierarchy process (AHP), the influencing factors of WCCM were identified and the identification model with a multilevel structure was developed, to determine the weight of each influencing factor. Based on this, the five maps: overburden thickness contour, stratigraphic structure map, water-rich zoning map of aquifers, aquiclude thickness contour and coal seam thickness contour, were analyzed and determined. This formed the basis for studying WCCM in the mining area. Using the geological conditions of the Yu-Shen mining area, the features of caved zone, water conductive fractured zone (WCFZ) and protective zone were studied. The equations for calculating the height of the “three zones” were proposed. Considering the hydrogeological condition of Yu-Shen mining area, the criteria were put forward to evaluate the impact of coal mining on groundwater, which were then used to determine the distribution of different impact levels. Using strata control theory, the mechanism and applicability of WCCM methods, including height-restricted mining, (partial) backfill mining and narrow strip mining, together with the applicable zone of these methods, were analyzed and identified. Under the guidance of “two zoning” (zoning based on coal mining’s impact level on groundwater and zoning based on applicability of WCCM methods), the WCCM practice was carried out in Yu-Shen mining area. The research findings will provide theoretical and practical instruction for the WCCM in the northwest mining area of China, which is important to reduce the impact of mining on surface and groundwater.

scholarly journals Development status and Prospect of directional hydraulic fracturing technology for coal mine roof

2020 ◽  
Vol 194 ◽  
pp. 01043
Author(s):  
LI Liangwei
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Large Scale ◽  
Evaluation Method ◽  
Field Application ◽  
Control Technology ◽  
Control Methods ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof ◽  
Extension Mechanism

Aiming at the harm and control methods of thick and hard roof in coal mine, the paper firstly analyzes the advanced control methods of thick and hard roof, such as directional shaped charge blasting roof control technology, hydraulic fracturing roof control technology, abrasive water jet directional cutting roof technology, large-scale special roof cutting machine, etc Control hole fracturing, transverse slotting fracturing and longitudinal slotting fracturing are compared and analyzed; finally, the shortcomings of current research are analyzed. According to the current research results, the analysis shows that: the method of controlling roof by blasting in the future will be limited, while the method of hydraulic fracturing, especially directional hydraulic fracturing, has obvious advantages; the longitudinal slotting fracturing has the best control over fractures in the directional hydraulic fracturing technology; the guiding mechanism and fracture extension mechanism of longitudinal slotting hydraulic fracturing in thick and hard roof need to be further studied; lack of field application research and corresponding equipment development, lack of field effect evaluation method after longitudinal slotting fracturing.

scholarly journals Mechanism of Hard-Roof Rock Burst Control by the Deep-Hole Blasting: Numerical Study Based on Particle Flow

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Anliang Lu ◽  
Linming Dou ◽  
Jinzheng Bai ◽  
Yanjiang Chai ◽  
Kunyou Zhou ◽  
...  
Keyword(s):  
Rock Burst ◽  
Roof Rock ◽  
Force Chain ◽  
Particle Flow ◽  
Hydraulic Pressure ◽  
Deep Hole ◽  
Key Strata ◽  
Hard Roof ◽  
Single Hole ◽  
Working Resistance

In underground coal mines, the deep-hole blasting (DHB) technology is generally adopted for thick hard-roof control. This technology uses the energy released by explosives to weaken the energy storage capacity of hard roof so as to prevent hard-roof rock burst disasters. In this paper, a numerical simulation model of roof DHB was established based on particle flow and the damage range of single-hole blasting with concentrated cylindrical charge was studied. The temporal and spatial evolutions of overlying strata, the distribution of the force chain structure, and the working resistance of hydraulic pressure in the mining process before and after the application of DHB were contrastively analyzed. The following beneficial conclusions were drawn. The blasting-induced single-hole damage range is generally characterized by annular zoning. After the application of DHB, overall the collapse morphology of the key strata in the mining process changes from long-distance instantaneous slipping instability to stratified short-arm stepped synergistic subsidence. The density and strength of force chains in the overburden are notably reduced; the peak value of compressive force chain strength in the key strata in the mining process falls by 17.85% as a result of DHB. The monitoring results of the working resistance of hydraulic support reveal that the DHB technology can effectively shorten the step distance of periodic weighting and reduce the variation amplitude of overburden load during weighting. In summary, the mechanism of hard-roof rock burst control by DHB is reflected by both static load reduction and dynamic load reaction.

Hybrid Combination of GIS,GPS,WSN and GPRS Technology in Modern Digital Agriculture Application

2010 ◽  
Vol 108-111 ◽  
pp. 1158-1163 ◽  
Author(s):  
Peng Cheng Nie ◽  
Di Wu ◽  
Weiong Zhang ◽  
Yan Yang ◽  
Yong He
Keyword(s):  
Large Scale ◽  
Field Application ◽  
Wireless Sensor ◽  
Information Collection ◽  
Scale Field ◽  
Large Scale Field ◽  
Field Information ◽  
Intelligent Management ◽  
Digital Agriculture ◽  
And Control

In order to improve the information management of the modern digital agriculture, combined several modern digital agriculture technologies, namely wireless sensor network (WSN), global positioning system (GPS), geographic information system (GIS) and general packet radio service (GPRS), and applied them to the information collection and intelligent control process of the modern digital agriculture. Combining the advantage of the local multi-channel information collection and the low-power wireless transmission of WSN, the stable and low cost long-distance communication and data transmission ability of GPRS, the high-precision positioning technology of the DGPS positioning and the large-scale field information layer-management technology of GIS, such a hybrid technology combination is applied to the large-scale field information and intelligent management. In this study, wireless sensor network routing nodes are disposed in the sub-area of field. These nodes have GPS receiver modules and the electric control mechanism, and are relative positioned by GPS. They can real-time monitor the field information and control the equipment for the field application. When the GPS position information and other collected field information are measured, the information can be remotely transmitted to PC by GPRS. Then PC can upload the information to the GIS management software. All the field information can be classified into different layers in GIS and shown on the GIS map based on their GPS position. Moreover, we have developed remote control software based on GIS. It can send the control commands through GPRS to the nodes which have control modules; and then we can real-time manage and control the field application. In conclusion, the unattended automatic wireless intelligent technology for the field information collection and control can effectively utilize hardware resources, improve the field information intelligent management and reduce the information and intelligent cost.

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

2021 ◽  
Vol 11 (9) ◽  
pp. 4125
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Zhengzheng Xie ◽  
Feng Guo ◽  
Chenghao Zhang
Keyword(s):  
Coal Seam ◽  
Cooperative Control ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Hole ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Structure Damage ◽  
Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

scholarly journals ECE laboratory in the Vinca institute: Its basic characteristics and fundamentals of electrochemic etching on polycarbonate

2003 ◽  
Vol 18 (2) ◽  
pp. 57-60 ◽  
Author(s):  
Zora Zunic ◽  
Predrag Ujic ◽  
Igor Celikovic ◽  
Kenzo Fujimoto
Keyword(s):  
Large Scale ◽  
Electrochemical Etching ◽  
Initial Step ◽  
Field Application ◽  
Alpha Particles ◽  
Experimental Phase ◽  
Laboratory Equipment ◽  
Etch Pit ◽  
Large Scale Survey ◽  
Basic Characteristics

This paper deals with the introductory aspects of the Electrochemical Etching Laboratory installed at the VINCA Institute in the year 2003. The main purpose of the laboratory is its field application for radon and thoron large-scale survey using passive radon/thoron UFO type detectors. Since the etching techniques together with the laboratory equipment were transferred from the National Institute of Radiological Sciences, Chiba, Japan, it was necessary for both etching conditions to be confirmed and to be checked up^ i. e., bulk etching speeds of chemical etching and electrochemical etching in the VINCA Electrochemical Etching Laboratory itself. Beside this initial step, other concerns were taken into consideration in this preliminary experimental phase such as the following: the measurable energy range of the polycarbonate film, background etch pit density of the film and its standard deviation and reproducibility of the response to alpha particles for different sets of etchings.

scholarly journals Brown Coal in Victoria, Australia and Maddingley Brown Coal Open Cut Mine Batter Stability

2020 ◽  
Vol 9 (3) ◽  
pp. 109-118
Author(s):  
Lei Zhao ◽  
Greg You
Keyword(s):  
Coal Seam ◽  
Brown Coal ◽  
Large Scale ◽  
Low Cost ◽  
Three Dimensional ◽  
Open Pit ◽  
Open Pit Mining ◽  
Mining Operations ◽  
Power Generators ◽  
Three Dimensional Finite Element

Brown coal is young, shallowly deposited, and widely distributed in the world. It is a fuel commonly used to generate electricity. This paper first reviews the resources and characteristics of brown coal in Victoria, Australia, and its exploitation and contribution to the economy or power supply in Victoria. Due to the shallow depth of the brown coal seam, e.g. very favorable stripping ratio, open pit mining is the only mining method used to extract the coal at low cost for power generators. With the large-scale mining operations, cases of batter failure were not rare in the area. From the comprehensive review of past failures, overburden batter tends to fail by circular sliding, coal batter tends to fail by block sliding after the overburden is stripped due to a weak water-bearing layer underneath the coal seam and tension cracks developed at the rear of the batter, and batter failure is typically coincided with peak raining seasons. Secondly, the paper reviews the case study of Maddingley Brown Coal (MBC) Open Cut Mine batter stability, including geology, hydrogeology, and hydro-mechanically coupled numerical modelling. The modelling employs three-dimensional finite element method to simulate the MBC northern batter where cracks were observed in November 2013. The comprehensive simulation covers an overburden batter, a brown coal batter, two rainfall models, and a buttressed batter. The simulated results agree well with observed data, and it is found that the rainfall at the intensity of 21mm substantially lowered the factor of safety of the coal batter.

scholarly journals Maintaining Mutual Benefits between Investor and Local Community: Mechanisms to Reopen Lega Dambi Gold Mining, Ethiopia

2021 ◽  
Vol 2 (1) ◽  
pp. 55-81
Author(s):  
Abdisa Olkeba Jima
Keyword(s):  
Corporate Social Responsibility ◽  
Social Responsibility ◽  
Large Scale ◽  
Gold Mining ◽  
Local Community ◽  
Local Communities ◽  
Mining Operations ◽  
Mining Company ◽  
Social License ◽  
Corporate Social

Mining, specifically, large-scale gold mining has become one of the primary economic activities that play a pivotal role in the socio-economic development of one country. But there is no consensus among scholars whether gold mining companies maintain mutual benefits with local communities. The main objective of this research is to scrutinize the mechanism to be employed in reopening Lega Dambi large-scale gold mining by maintaining mutual benefits between the company and the local community. The researcher employed a qualitative method and a case study research design. Focus group discussions and semi-structured interviews were used to collect data from the local community, elders, religious leaders, Abbaa Gadaas, Guji Zone, and Odo Shakiso Woreda investment office, land management office, social and labor affair, mineral, and energy office administrators, and Odo Shakiso Woreda health station and Adola hospital. Secondary sources and regulatory frameworks such as FDRE Constitution and Mining Operations Proclamation No. 678/2010 were used to triangulate with primary data. The finding shows that Lega Dambi's large-scale gold mining company failed to maintain mutual benefits between itself and the local community. Basic tenets such as national and regional corporate social responsibility, community development agreement, impact and benefit agreements, social and labor plan, and social license were not implemented properly to balance the mutual benefit between the company and the local community. The researcher concluded that Lega Dambi large-scale gold mining company disregarded the role of the local community during commencement time albeit it had a strong relationship with the central government. Consequently, the company was terminated because of a bad relationship it had with the local community. It is recommended that national and regional corporate social responsibility that shows the company’s specific joint administration of the central and Oromia region governments should be designed and implemented fully. It is also recommended that discussions should be held with local communities and arrived at a consensus concerning the reopening of the company.

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