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Numerical simulation on effect of coal pillar width on stability of retained roadway: A case study of Khe Cham Coal Mine, Vietnam

Le Quang Phuc, Le Tien Dung

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 1

1--9

EN

When extracting coal seams in Vietnam underground mines, coal pillars are often left unmined for the protection of retained roadways in the longwall mining method. During longwall mining operations, coal pillars are often placed where high-stress concentrations occur in the abutment pressure zone of adjacent panels, especially when extracting seams under hard-to-cave main roof conditions. The instability of coal pillars under the loading of the main roof may cause the roadway to collapse, threatening the safe operation of a coal mine. This paper presents a detailed numerical investigation of the effect of coal pillar width on the stability of retained roadway under hard-to-cave main roof conditions, which has not been fully understood in previous studies. The results indicate that as the width of the coal pillar increases, the peak stress gradually moves from the virgin coal side to the pillar side, and an elastic zone will gradually be formed in the center of the pillar. A pillar width of less than 40 m coal pillars is easily destroyed under the great pressure caused by the hard main roof. A pillar width greater than 40 m creates a safe condition and has enough bearing capacity to maintain the stability of retained roadways. Based on these results, this paper proposes to use an improved longwall mining method where the coal pillars should be mined together with the adjacent panel to reduce coal loss in pillars.

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Stress Distribution Around Mechanized Longwall Face at Deep Mining in Quang Ninh Underground Coal Mine

Bui Manh Tung, Le Tien Dung, Vo Trong Hung

Inżynieria Mineralna

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2021

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no. 2

167--176

EN

Quang Ninh underground coal mines are currently in the phase of finishing up the mineral reserves located near the surface. Also, in this phase, a number of coal mines have opened and prepared new mine sites for the extraction of the reserves at greater depth. Several mines have mined at -350 m depth and are driving opening excavations at -500 m depth below sea level. The mining at greater depth faces many difficulties, such as a significant increase in support and excavation pressures. The longwall face pressure is mostly manifested in great magnitude that causes support overloaded and jumped and face spall/roof fall. This paper, based on the geological condition of the Seam 11 Ha Lam coal mine, uses the numerical program UDEC for studying the impact of mining depth on stress distribution around the longwall face. The results show that the deeper the mining is, the greater the plastic deformation zone is. The peak front abutment stress moves closer to the coal wall, mainly concentrating on the immediate roof and top coal. The top coal is greatly broken, and its bearing capacity is decreased. Some solutions to the stability of roof strata are proposed, and a proper working resistance of support is determined. Additionally, the paper suggests that the starting depth for deep mining in Quang Ninh underground coal mines should be -350 m below sea level.

3

Research, Calculation and Proposal of Ventilation Solution for Duong Huy Coal Mine when Mining Down to -250 m Depth

Dao Van Chi, Le Tien Dung, Vu Thai Tien Dung, Nguyen Hong Cuong

Inżynieria Mineralna

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2021

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no. 2

513--520

EN

At present, according to the extraction plan in the year 2020 of Duong Huy Coal Company - Vinacomin, the mining is divided into three main zones: Central Zone extracts 06 faces; South Zone extracts 2 faces and Northeast Zone extracts 2 faces. The designated total production of all zones is 1,880,000 tons/year. To ensure the production of each mining zone, exhaust fan stations are installed at ventilation roadway adits with a total of 05 main fan stations. However, in the near future, to ensure and maintain production activities, the mine is being planned and operated using 03 main fan stations. The calculation results for the reasonable working mode of fan stations are as follows: for fan station FBCDZ8-№32B at level +47 m, airflow is 167.69 m3 /s and air pressure is 243.74 mm H2O; for fan station 2K56- №30 level +40 m, airflow is 123.37 m3 /s and air pressure is 324.79 mm H2O; for fan station FBCDZ-8- №32B at level +44 m, airflow is 167.69 m3 /s and air pressure is 354.99 mm H2O.

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Development of Support Plan and Operation Scheme for Semi-mechanized Longwall Face of Coal Seam 10T, Nam Khe Tam Mine – 86 Company, Dong Bac Corporation

Vu Trung Tien, Le Tien Dung, Vu Thai Tien Dung

Inżynieria Mineralna

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2021

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no. 2

321--330

EN

Support plans and operation schemes of mine faces are critical technical documents in underground coal mining management. The development and selection of a reasonable support plan and operation scheme of the face are complicated because they involve many factors. In specific mining conditions, developing and selecting an appropriate support plan and operation scheme will improve the working efficiency of equipment, increase labor productivity, and ensure workers' safety. This article researched a mining technology for the thin seams, focusing on coal seam 10T in Nam Khe Tam coal mine, 86 Coal Company. From the analysis of geo-mining conditions, the article developed and selected a reasonable support plan and operation scheme for the face in coal seam 10T. After being used in the field, the support plan and operation scheme have brought the face efficiency and safety.

5

Study on Controlling Parameters and Technological Optimization of Strip Longwall Top Coal Caving in Thick Coal Seams

Bui Manh Tung, Le Tien Dung, Liu Chang You, Pham Van Chung

Inżynieria Mineralna

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2020

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no. 2, vol. 1

105--113

EN

Based on the geological and mining conditions of face 3107 at Liang Baoshi coal mine, China, the numerical programs FLAC3D 2.10 and PFC2D 2.10 were used to analyze the parameters controlling the failure, caving and the coal recovery rate in Strip Longwall Top Coal Caving (SLTCC). The analyzed parameters are face length in dip direction, mining height, the span of coal caving, and sequence of coal drawing. The results show that the application of SLTCC for a limited face length is not favourable to coal failure, and it increases top coal loss. A sound engineering selection of technological parameters is therefore important to efficient mining in thick coal seams. The numerical results show that a face design of 3 m of cutting height, 0.8 m of caving span, and alternate drawing sequence results in high coal recovery rate, simple mining tasks, and efficient operation of face equipment.

PL

W oparciu o warunki geologiczno-górnicze przodka 3107 w kopalni Liang Baoshi w Chinach, oprogramowanie FLAC3D 2.10 i PFC2D 2.10 zostało wykorzystane do analizy parametrów wpływających na awarię, zawał i stopień odzysku węgla stropowego w zmechanizowanym wyrobisku eksploatacyjnym. Analizowanymi parametrami są długość przodka, wysokość urabiania, rozpiętość i kolejność zawału stropowego. Wyniki pokazują, że zastosowanie SLTCC przy ograniczonej długości ściany nie sprzyja awariom węgla i zwiększa ubytki górne. Dlatego odpowiedni dobór parametrów technologicznych jest ważny dla efektywnej eksploatacji w grubych pokładach węgla. Wyniki liczbowe pokazują, że projekt przodka o 3 m wysokości urabiania, 0,8 m rozpiętości zawału i z naprzemienną kolejnością skutkuje wysoką wydajnością wydobycia węgla, prostą technologią wydobywczą i wydajną pracą urządzeń przodkowych.

6

Safe Exploitation Solution and Reduction of Resources Loss for the L7 Seam at the West Wing Area of the 790 Open Pit Site of the Mong Duong Coal Mine

Pham Duc Hung, Le Tien Dung, Nguyen VanQuang

Inżynieria Mineralna

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2020

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no. 2, vol. 1

231--238

EN

In the next time, deepening exploitation and increasing capacity in underground mines are extremely necessary to meet the demand of using coal for developing economies. This problem is not only done in underground mines but also in areas that cannot be exploited by open-pit methods such as the open-pit edge. When exploiting deep underground mines, there are many difficulties for tasks such as: controlling ground pressure; ventilation; drainage, transportation etc. When cutting coal in longwall, it will create a goaf, causing a natural imbalance of stress in the ground, leading to the phenomenon of displacement of rock deformation and destruction of roadways, which creates a risk of unsafety labour. The L7 seam at the west wing area of the Mong Duong coal mine has an average thickness of 7m, an average slope angle of 15o, located near the edge of the 790 open pit site. According to the production plan, this mine will exploit this reservoir with blasting-drilling technology, longwall support by the semi-mechanized shield (self-moving hydraulic frame GK/1600/16/24/HTD). The preliminary assessment of hydrogeological conditions of the mine shows that this is a potential area with a high risk of water burst into the longwall. Until now this mine has not yet given a specific solution to this problem. Finding a reasonable mining solution to ensure production safety and reduce resources loss is extremely important problem not only for the Mong Duong coal mine but also for mines that have similar mining conditions of Vietnam National Coal – Mineral Industries Holding Limited (Vinacomin), Vietnam.

PL

W ostatnich latach, w Wietnamie intensywnie prowadzono nie tylko rozbudowę i modernizację istniejących kopalń lecz także zagospodarowano nowe złoża na szeroką skalę. W górnictwie podziemnym istnieje wiele ważnych problemów technicznych, które należy rozwiązać, mianowicie: ciśnienie, wentylacja, trans-port podziemny, odwadnianie itp. Wykonanie wyrobiska powoduje zaburzenie początkowego stanu równowagi w górotworze nienaruszonym, skutkiem czego w otoczeniu wyrobiska zmieniają się naprężenia których wartość jest większa od naprężeń początkowych. Odprężenie górotworu w otoczeniu wyrobiska górniczego powoduje przemieszczanie się skał w kierunku pustej przestrzeni. Pokład L7 w zachodnim skrzydle kopalni Mong Duong ma średnią miąższość 7 m, średni kąt nachylenia 15 ° znajduje się w pobliżu krawędzi odkrywki 790. Zgodnie z planem wydobycia kopalni, zakład górniczy Mong Duong będzie kontynuować eksploatację tego pokładu z technologią wiercenia strzałowego, podparcie ściany za pomocą pół-zmechanizowanej osłony (samojezdna rama hydrauliczna GK / 1600/16/24 / HTD). Wyniki badań warunków hydrogeologicznych kopalni wskazują, że obszar badany jest potencjalny o dużym ryzyku wtargnięcia wody do ściany. W artykule, przedstawiono odpowiednie rozwiązania technologii wydobywczej, które zabezpieczają kopalnię przed zagrożeniem wodnym i ograniczy straty zasobów. Opracowana metoda jest zastosowana nie tylko dla kopalni Mong Duong, ale także i dla kopalń należących do Vinacomin, które mają podobne warunki górniczo-geologiczne.

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Estimation of Coal and Rock Mechanical Properties for Numerical Modelling of Longwall Extraction

Le Tien Dung, Nguyen Chi Thanh, Dao Van Chi

Inżynieria Mineralna

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2020

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no. 2, vol. 1

41--47

EN

Reliable estimation of coal and rock mechanical properties at field scale is a prerequisite for numerical modelling of rock behaviours associated with longwall extraction. This paper describes a systematic approach from data collection, laboratory testing to rock mass properties derivation for simulation of longwall extraction, taking two longwall panels at Quang Ninh coalfield in Vietnam for example. The mechanical properties are verified through comparison with published data of the field, indicating close agreements. A simple numerical model is further developed to demonstrate the proper use of the obtained data. The simulation suggests that the ratio of model length to excavation length should be in the range of 2.5–5; uniaxial compressive strength, deformation modulus and tensile strength can be reduced by a factor of 5.0, 2.13 and 2.0, respectively; and a calibration and validation process must be performed to match in-situ longwall’s behaviours. The approach can be applied for derivation of reliable rock mass properties for numerical simulation of underground excavations.

PL

Rzetelne oszacowanie właściwości mechanicznych węgla i skał w skali polowej jest warunkiem koniecznym do numerycznego modelowania zachowań skał związanych z eksploatacją ścianową. W artykule, opisano systematyczne podejście od gromadzenia danych, badań laboratoryjnych do wyznaczania właściwości górotworu w celu symulacji eksploatacji ścian, na przykład na dwóch panelach ścianowych na polu węglowym Quang Ninh w Wietnamie. Właściwości mechaniczne są weryfikowane poprzez porównanie z opublikowanymi danymi polowymi, wskazując na bliskie uzgodnienia. Dalej rozwijany jest prosty model numeryczny w celu zademonstrowania właściwego wykorzystania uzyskanych danych. Symulacja sugeruje, że stosunek długości modelu do długości wykopu powinien zawierać się w przedziale 2,5–5; jednoosiową wytrzymałość na ściskanie, moduł odkształcenia i wytrzymałość na rozciąganie można zmniejszyć odpowiednio o współczynnik 5,0, 2,13 i 2,0; oraz należy przeprowadzić proces kalibracji i walidacji, aby dopasować zachowanie ściany na miejscu. Podejście to można zastosować do wyprowadzenia wiarygodnych właściwości górotworu do numerycznej symulacji podziemnych wyrobisk.

8

Status and prospects of underground coal mining technology in Vietnam

Le Tien Dung, Bui Xuan‑Nam

Inżynieria Mineralna

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2019

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R. 21, nr 2/2

105--111

EN

Underground coal mining in Vietnam plays an important role to not only the sustainable coal industry but also the energy and social security in this country. Although the Vietnam coal industry has produced 35–45 million tonnes of raw coal per annum in past ten years, a great volume of coal resources remains distributed in complex geo-mining conditions and mostly unmined. This paper presents a brief review of the current and potential technologies for cutting coal and controlling roof in Vietnam underground coal mines. From the review, it is concluded that there is an urgent demand on improvement of current technologies as well as on investigation for effective application of more advanced mining methods into the industry, especially for deep mining at Red River Delta—the largest coal basin in Vietnam.

9

Geotechnical mechanisms of roof fall ahead of face support in longwall mining

Le Tien Dung, Duc Hung Pham, Quang Hung Dang

Inżynieria Mineralna

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2019

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R. 21, nr 2/2

98--104

EN

Longwall mining is one of the most productive methods for extracting underground coal seams. Although the understanding of longwall mining-associated geotechnical mechanisms has been significantly improved that contributes to better ground control, roof rock/top coal fall ahead of support (roof fall) has not been fully understood that causes severe damage to equipment and casualty at face. Empirical, theoretical and modelling methods were successfully used in past studies to understand the mechanisms driving roof fall; however, key mechanisms and their interactions during the fall were not satisfactorily investigated due to limitation of each method. This study aims to gain a systematic understanding of roof fall mechanisms in longwall operation. A review of past studies on roof fall is implemented with emphasis on the principles of applied research methods. The study confirms that the interaction between roof strata, coal seam and face support largely controls roof fall while numerical modelling shows great potential in studying roof fall complex mechanisms. The paper’s findings provide mining engineers/scientists with a systematic understanding on roof fall from which more effective roof control strategies can be further developed.

10

Application of information technology to improve the management of mineral resources in Quang Ninh province - Vietnam

Dao Van Chi, Nguyen CaoKhai, Le Tien Dung, Zhang Leilin

Inżynieria Mineralna

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2019

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R. 21, nr 2/2

217--222

EN

The current mining operation of mineral resources in Quang Ninh province-Vietnam is increasingly complicated. Correspondingly, the management of the mine sites becomes more difficult. Records and documents of minerals and mine sites are archived in different forms. Database systems are stored dispersedly and insufficiently; in many cases lack accuracy, topicality and have not been linked to each other systematically. These lead to many difficulties in accessing and extracting information for the implementation of management as well as for investors and people with related interest. In this paper an advanced software has been developed for the management of mineral resources and has been applied for Quang Ninh province. The software has improved the supervision and administration of the mining operation in the province.