Study on Roof‐Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining

Li, Lei; Li, Xuelong; Wang, Kequan; Chen, Jinhua; Sun, Zhongguang; Yang, Xuelin

doi:10.1155/2019/6519213

Cited by 15 publications

(10 citation statements)

References 36 publications

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“…As mentioned in the introduction, carrying out mining processes in intact rock mass causes its imbalance [30,31] which affects excavation and the support system protecting it. This impact may have a different character and be the result of various phenomena occurring in the rock mass [5,[32][33][34][35][36]. A list of these phenomena and their effects on the support is shown in Figure 2.…”

Section: Phenomena Occurring In the Exploited Rock Mass And Their Effmentioning

confidence: 99%

Adapting the Powered Roof Support to Diverse Mining and Geological Conditions

Szurgacz

Brodny

2020

Energies

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A powered roof support is one of the most important machines of a longwall system. Its basic task is to ensure the safety and continuity of the mining process. The conditions of coal mining process are constantly changing and have significantly deteriorated in recent years, which in turn has also resulted in a significant increase in the requirements for mining support. As a result, it is necessary to develop an appropriate methodology that will facilitate the design and testing process of a power roof support as well as will help to select a roof support adjusted to given conditions. The article presents such a methodology. It is based on forecasted load impacting on a roof support, tests covering selected systems and elements of the section as well as legal conditions regarding the admission of the roof support to operation. This idea was developed in the form of a procedure that, by combining the three areas, should support the decision-making process in the case of different underground conditions. In terms of the expected load impacting on the support, the research team identified the most dangerous phenomena occurring in the rock mass that can generate these loads. Stand tests included impact load and permanent clamping of an excavation. The element that significantly impacts the safety of the support operation is a hydraulic leg, and therefore it was tested together with the safety system and the control system. Model tests were also carried out for the system with a safety valve. The developed concept takes into account legal conditions, which should include test results and different support operating conditions in a more flexible way. The main purpose of the work was to develop a comprehensive methodology for testing and assessing the possibility of using a powered roof support for given mining and geological conditions based on an analysis of safety and control systems. The presented approach is undoubtedly new and original, and can be widely used. It enables better adaptation of the support to given conditions. It also fits the research and activities designed to minimize the presence of miners or service workers in hazardous underground exploitation zones and to improve efficiency and boost sustainable development of the mining industry.

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Section: Phenomena Occurring In the Exploited Rock Mass And Their Effmentioning

confidence: 99%

Adapting the Powered Roof Support to Diverse Mining and Geological Conditions

Szurgacz

Brodny

2020

Energies

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“…The study showed that as the weighted average particle size of the top coal increased, the volume of DB increased linearly and the maximum width of it increased non-linearly; as the weighted average particle size of the top coal increased, the top coal recovery ratio tended to increase and then decreased; high recoveries were achieved when the weighted average particle size of the top coal was in the range of 150-250 mm; and a relatively dispersed top coal particle size distribution and large standard deviations [13] were more favorable for the drawing of the top coal. Liang et al [14] studied the drawing characteristics of complex top coal, and believed that the cutting-caving ratio had an important influence on the drawing of the top coal. In the absence of manual intervention to break the coal, a cutting-caving ratio of 3 was most favorable for the drawing of the top coal.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

et al. 2021

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In longwall top coal caving (LTCC), the resource recovery ratio of the working face is directly determined by the top coal recovery ratio. An investigation of the evolution of top coal drawing characteristics and revealing the evolution of top coal drawing parameters is necessary when providing guidance for caving parameter selection and improving the top coal recovery ratio. Based on in-situ measurements of the size distribution of caved top coal blocks in Wangjialing coal mine, a finite difference method (FDM)–discrete element method (DEM) coupled method was applied to establish a “continuous–discontinuous” numerical model and the process from the first coal drawing to the common coal drawing was simulated with 17 separate working face advances. The evolution of the drawing body (DB), loose body (LB), and top coal boundary (TCB) was obtained. The results show that, the evolution of parameters of DB such as shape and size, drawing amount, length and deflection angle of the long axis of the profile ellipsoid tended to decrease first, then increase, decrease again, and finally stabilise; the increment of the LB advance coal wall distance and the coal pillar distance was close to 0 m in the common coal drawing stage, while width increment of the LB was close to the drawing interval (0.865 m). The TCB formed after each coal drawing round was fitted based on the improved “Hook” function. The evolution of height and radius of curvature of TCB’s stagnation point was analysed. This was divided into three stages: the first (first to third drawing rounds) was the initial mining influence stage, the second (fourth to ninth drawing rounds) was the transitional caving stage, and the third (after tenth drawing round) was the common coal drawing stage.

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“…This particularly applies to mining roof supports [1][2][3][4][5][6][7][8]. Their primary task is to protect mining excavations against deformation caused by the rock mass [1][2][3][4][5][6][7][8][9][10]. Therefore, in order to protect mine workings, various types of mining roof support are used [1][2][3]11,12].…”

Section: Introductionmentioning

confidence: 99%

“…However, the hydraulic system and its control system are of particular importance due to the efficiency of the operation process itself, and the possibility of impact on the operating parameters of the section and the support. In this respect, hydraulic legs fulfil are executive elements that largely determine the effectiveness of the entire support being exposed to static and dynamic loads [6,7,20,21].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Influence of Dynamic Load on the Work Parameters of a Powered Roof Support’s Hydraulic Leg

Szurgacz

Brodny

2019

Sustainability

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One of the basic tasks of powered roof support is to protect the longwall excavation against deformation of the rock mass during the underground exploitation of hard coal. The behavior of the rock mass during mining is difficult to predict. Therefore, the loads acting on the support are diverse in terms of nature, direction and force. The dynamic load resulting from rock bursts, relaxation and tremors may lead to particularly dangerous consequences involving the functionality of the workings and the safety of the crew. The powered roof support will function properly only if the elements dynamically loaded are under control at the moment of impact. The article presents the results of tests of the basic powered roof support’s element − a hydraulic leg impacted by dynamic load. The source of the load was a free falling impact mass dropped from a certain height. The tests covered the actual hydraulic leg with all hydraulic equipment used in the powered roof support. During the tests, the original measurement-recording system developed by the authors was used, in which, among others, a high-speed dynamic camera was used to record movements of the leg’s elements. The original research methodology developed together with the measurement system enabled the registration of many parameters of the leg’s work under dynamic load. In particular, this applies to time series of pressure in the leg and the value of its withdrawal depending on the energy of the impact. The individual phases of the leg’s work were also registered, including the opening and closing of the safety valve protecting the leg against overloading. The obtained results broaden knowledge in the field of hydraulic legs used in the mining support under dynamic load. At the same time, they are a valuable source of information for mine maintenance services and should be applied to the design process, selection and operation of a powered roof support in dynamic conditions. The subject of the article fits in with the philosophy of sustainable development, especially in the field of full use of options of the support and ensuring safe and environmentally friendly mining processes.

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Study on Roof‐Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining

Cited by 15 publications

References 36 publications

Adapting the Powered Roof Support to Diverse Mining and Geological Conditions

Adapting the Powered Roof Support to Diverse Mining and Geological Conditions

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

Analysis of the Influence of Dynamic Load on the Work Parameters of a Powered Roof Support’s Hydraulic Leg

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