Wyniki wyszukiwania - Biblioteka Nauki

1

Impact of longwall mining on slope stability – A case study

100%

Nguyen P. M. V.

Studia Geotechnica et Mechanica

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2022

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tom Vol. 44, nr 4

282--295

EN

In recent decades, many open pit (OP) mines have either already made the decision or are at the planning stage to change their mining activity from OP to underground (UG) to remain competitive. Technically, before the OP ends its operation, both OP and UG mining will have to be operated simultaneously for a certain period of time. It is well known that UG operation causes subsidence, discontinuous deformations, and changes in hydrogeological conditions. In case of UG operation located below the OP mine, slope deformation can be expected as a result of subsidence induced by UG exploitation. This paper presents a numerical analysis of slope stability under the influence of the longwall mining operation at the Cao Son OP mine in Vietnam. All calculation variants were performed using the Finite Difference Method code, FLAC. In order to evaluate slope stability of the OP slope, various geometry configurations showing advances of both OP and UG extractions were examined. Based on the outcomes, assessments on OP slope are presented, and then, practical actions regarding the location and direction of UG extraction are recommended, with an aim to minimize the impact of underground mining on OP slope.

2

Geomechanical assessments of longwall working stability – a case study

51%

Nguyen P. M. V. , Rajwa S. , Płonka M. , Stachura W.

Archives of Mining Sciences

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2022

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tom Vol. 67, no. 2

333--354

EN

The stability of longwall mining is one of the most important and the most difficult aspects of underground coal mining. The loss of longwall stability can threaten lives, disrupt the continuity of the mining operations, and it requires significant materials and labour costs associated with replacing the damages. In fact, longwall mining stability is affected by many factors combined. Each case of longwall mining has its own unique and complex geological and mining conditions. Therefore, any case study of longwall stability requires an individual analysis. In Poland, longwall mining has been applied in underground coal mining for years. The stability of the longwall working is often examined using an empirical method. A regular longwall mining panel (F3) operation was designed and conducted at the Borynia-Zofiówka-Jastrzębie (BZJ) coal mine. During its advancement, roof failures were observed, causing a stoppage. This paper aims to identify and determine the mechanisms of these failures that occurred in the F3 longwall. A numerical model was performed using the finite difference method - code FLAC2D, representing the exact geological and mining conditions of the F3 longwall working. Major factors that influenced the stability of the F3 longwall were taken into account. Based on the obtained results from numerical analysis and the in-situ observations, the stability of the F3 longwall was discussed and evaluated. Consequently, recommended practical actions regarding roof control were put forward for continued operation in the F3 longwall panel.

3

An investigation of longwall failure using 3D numerical modelling – A case study at a copper mine

51%

Nguyen P. M. V. , Olczak T. , Rajwa S.

Studia Geotechnica et Mechanica

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2021

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tom Vol. 43, nr 4

389--410

EN

It is well-known that the longwall mining method (with roof caving) is widely used in underground mining extraction for bedded deposits (e.g. coal) due to its numerous advantages. Generally, this method is not commonly applied for ore deposits such as copper deposit. In Poland, the longwall mining method has been tested for thin copper deposits at the Polkowice-Sieroszowice copper mine (KGHM). Various failure modes were observed during longwall operation in the 5A/1 panel. This paper aims to examine these occurred failures. To do so, an analysis has been conducted using 3D numerical modelling to investigate the failure mode and mechanism. Based on the 3D numerical modelling results with extensive in situ measurements, causes of failure are determined and practical recommendations for further copper longwall operations are presented.

4

Municipal waste management based on geomechanical assessments of the landfill site slope - a case study in southern Poland

51%

Janoszek T. , Nguyen P. M. V. , Grabowski J.

Journal of Sustainable Mining

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2024

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tom Vol. 23, iss. 2

185--198

EN

Over time, municipal waste landfills tend to go higher and become larger. The stability of the municipal landfill slope is one of the basic geotechnical tasks. This task ensures continuous waste deposition on the landfill surface and safety in its surroundings. With the increasing height and volume of the landfill, it is difficult to estimate the available area of the municipal landfill, where more waste can be safely deposited due to a number of variable factors, such as the geotechnical conditions of the municipal landfill, the morphological composition, age, and degree of compaction and decomposition of the deposited waste. This paper presents an attempt to determine the available area of a landfill where municipal waste can be safely deposited for further operation. For this purpose, a numerical slope stability analysis was carried out using the finite difference method code FLAC3D, presenting the actual geomechanical conditions of a landfill located in southern Poland. Based on the numerical results, options for municipal waste storage were presented and discussed. The proposed design chart aims to help landfill owners/managers make an adequate decision in terms of landfill planning and design.

5

Analysis of behaviour of the steel arch support in the geological and mining conditions of the Cam Pha coal basin, Vietnam

51%

Nguyen P. M. V. , Rotkegel M. , Van H. D.

Archives of Mining Sciences

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2020

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tom Vol. 65, no. 3

551--567

EN

In recent years, the Vietnamese coal mining industry has observed a dynamic increase in both its production and efficiency. In Vietnam, the most precious type of coal is anthracite, which is found in the Quang Ninh province. Industrial anthracite deposits are estimated to be over 2 billion Mg. At present, coal deposits are extracted mostly by the underground method. Coal production is gradually increasing in the underground mines in the Quang Ninh area and it is expected to constitute about 75% of the country’s total coal production in 2030. This involves an increase in the number and length of underground workings. Cam Pha is the largest coal basin of Vietnam, located in the Quang Ninh province. So far, the yearly length of underground workings driven in underground mines in the Cam Pha basin is roughly 90÷150 km. About 84 % of these underground workings are supported by the steel arch support made of SWP profile. A similar situation can be observed in Russia, Ukraine, China, India and Turkey. In addition, the average length of repaired underground workings in the Cam Pha basin constitutes approximately 30% of the total length driven . The main cause was reported is loss of underground workings stability. This requires significant material and labour costs as well as the cost of replacing damaged elements. Addi-tionally, it disturbs the continuity of the mining operations.This article presents the results of the numerical modelling of the rock mass around underground wor-kings driven in typical geo-mining conditions for underground coal mines in the Cam Pha basin, supported by the steel arch support made of SWP and V profiles. As a result of the conducted analyses, the range of failure zone of the rock mass around underground workings and the distribution of reduced stress in the steel arch support elements were determined. The effort states of the steel arch support made of SWP22 profile and V21 profile were compared. The simulations considered different inclinations angle of coal seam, following the structure of the rock mass in the Cam Pha basin. The analysis was carried out using the based-finite difference method code, FLAC2D. Based on the obtained results, actions for improving the stability of underground workings driven in the underground mines of the Cam Pha basin were proposed.

6

Numerical modelling of uniaxial compressive strength laboratory tests

45%

Nguyen P. M. V. , Walentek A. , Waclawik P. , Souček K. , Antoniuk M.

Journal of Sustainable Mining

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2023

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tom Vol. 22. iss. 4

280--294

EN

In the last decades, numerical modelling has been widely used to simulate rock mass behaviour in geo-engineering issues. The only disadvantage of numerical modelling is the reliability of required input data (e.g. mechanical parameters), which is not always fully provided due to the complexity of rock mass, project budget, available test methods or human errors. On the other hand, it was proven in many cases that numerical modelling is a helpful tool for solving such complex problems, especially when coupled with the results of laboratory and in-situ tests. This paper presents an attempt to determine the proper numerical constitutive model of rock and its mechanical parameters for further simulating rock mass response based on the outcomes of laboratory testing. For this purpose, the available constitutive models, including mechanical parameters, were taken into account. The simulation performance with the selected constitutive models is demonstrated by matching the numerical modelling results with the uniaxial compressive strength laboratory tests of rock samples from the Bogdanka coal mine. All numerical simulations were carried out using the finite difference method software FLAC3D.