In situ investigations into overburden failures of a super-thick coal seam for longwall top coal caving

Yu, Bin; Zhao, Jun; Kuang, Tiejun; Meng, Xiuxia

doi:10.1016/j.ijrmms.2015.05.009

Cited by 83 publications

(56 citation statements)

References 14 publications

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“…Generally, if the key strata are close to the coal seam or the thickness of coal seam is large, the key strata will be located in the caving zone and form a cantilever beam structure (CBS), while if the key strata siting is far away from the coal seam or located in the fractured zone, it will be hinged together (i.e., the broken blocks of key strata can be hinged with each other) to form a voussoir beam structure (VBS) [24], as shown in Figure 10a. According to the observed results of the height of the caving zone in the longwall top-coal caving face of the extra-thick coal seam in the Datong coalfield [2] and the determination method of the structure of the key strata [24], it can be concluded that the sub-key stratum (SKS) 1 of LTCC-west8101 forms the CBS, whereas the SKS 2 (main roof) forms the VBS, as shown in Figure 10b. Prior to the determination of support capacity, the structural characteristics of key strata [25], which control the overlying strata movement, should be identified.…”

Section: Determination Of Reasonable Support Capacitymentioning

confidence: 95%

“…At this point, according to Figure 11b,c the acceptable support capacity can be calculated by Equation (2).…”

Section: Determination Of Reasonable Support Capacitymentioning

confidence: 99%

“…The main mining seam is the carboniferous, extra thick coal seam 3-5# and its thickness ranges from 9.8 m to 30 m with an average thickness of 15 m [2]. The thickness of the coal deposit is a main factor in determining the exploitation system.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, few studies research the influence of top-coal properties and its movement regulation on strata behavior. Some have attributed chock support failure to the instability of the overlying strata structure [2,21,22], and the most common preventive measure is to reduce the mining height. In this case, the loss of coal resources would be inevitable in order to ensure safe mining.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Prevention of a Chock Support Failure in the Longwall Top-Coal Caving Faces: A Case Study in Datong Coalfield, China

Zhu

et al. 2018

Energies

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Longwall chock support failures seriously restrain the safety and high-efficiency of mining of extra thick coal seams, as well as causing a great waste of coal resources. During longwall top-coal caving (LTCC), the influential effect of the properties and the movement regulation of top-coal on strata behavior cannot be ignored, since the top-coal is the medium through which the load of the overlying strata is transferred to the chock supports. Taking Datong coalfield as an example, the mechanism of a chock support failure in the LTCC face was investigated. Research findings indicated that the hard top-coal and insufficient chock support capacity were primary reasons for chock support failure accidents. On account of the field-measured results, a new method to determine support capacity was proposed, which fully took the impact of the top-coal strength into consideration. The calculation revealed that the required support capacity had exceeded the existing production maximum, at about 22,000 KN. Since it was unrealistic to simply increase chock support capacity, other approaches, according to the theoretical analysis, were proposed, such as lowering the integrity and strength of the top-coal, and upgrading its crushing effect to weaken the support load effectively during the weighting period, which reduces the likelihood of chock support accidents occurring. Based on this, hydraulic fracturing for hard top-coal and optimization of the caving process (chock supports raised up and down repeatedly by manual operation before moving forward) were presented. The proposed solutions were successfully applied in LTCC-west8101 for subsequent mining and achieved substantial benefits. The above research provides valuable references and ideas for the control of strata behavior to ensure safe and highly efficient mining in extremely thick and hard coal seams with the LTCC method.

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Section: Determination Of Reasonable Support Capacitymentioning

confidence: 95%

“…At this point, according to Figure 11b,c the acceptable support capacity can be calculated by Equation (2).…”

Section: Determination Of Reasonable Support Capacitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanism and Prevention of a Chock Support Failure in the Longwall Top-Coal Caving Faces: A Case Study in Datong Coalfield, China

Zhu

et al. 2018

Energies

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“…The most frequently used methods to evaluate efficiency of underground support are laboratory testing (Hadjigeorgiou & Potvin, 2011;Tatone & Grasselli, 2015) and actual measurement of ground movement and support deformation (Yu, Zhao, Kuang & Meng, 2015;Zhang, Bai & Chen, 2015). Results of such tests and measurements provide very important if limited data because of cramped underground conditions, difficulty of access into rock mass and safety concerns.…”

Section: Introductionmentioning

confidence: 99%

Implementing FLAC3D model for simulating deformation mechanism of steel frame support set by actual profile

Nazymko¹,

Griniov²

2016

Min. miner. depos.

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Purpose. The problem of simulating steel frame irreversible deformation and displacement remains unsolved. The purpose of this research was to develop a new approach to simulation of frame yield support.Methods. We used combination of different methods, namely FLAC3D model, benchmark tests and materialistic frames profile in the form of primitive proxies in place of standard structural elements, for instance, beams, which are actually mathematical lines that have abstract geometrical characteristics of the frame profile.Findings. The research focused on the interaction of steel frame supports and the surrounding rocks during tail entry maintenance behind the longwall face to provide direct flow of air, which reduces methane explosion hazard.Originality. The proposed profile model can be helpful as a practical tool that can assist in frame support improvement during complex interaction of rock massif with frame support in difficult geological and geomechanical conditions. Practical implications.Owing to this approach, we were able to obtain practically all patterns of the actual frame profile behavior: frame turn and displacement, plastic hinge in coffering, longitudinal twisting and splitting, lateral bending, breakage and sliding in yield joints. Surprisingly, frame support behavior in computer model was extraordinary realistic despite primitive approximation of the frame profile, which demonstrates originality of the new approach.

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Optimization of drawing sequence in longwall top coal caving mining through an FDM‐DEM model

Huo,

Wang,

Zhu

et al. 2024

Energy Science & Engineering

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The Longwall top coal caving (LTCC) technology is regarded as one of the most crucial approaches for exploiting thick coal seams. A crucial and effective approach for improving the recovery rate of top coal and reducing coal resource losses in LTCC faces is to reasonably select process parameters based on actual mining and geological conditions of different mines. The main focus of this paper is the engineering background of the 12,309 LTCC face in Wangjialing Coal Mine. A numerical model is developed using FALC3D and PFC3D software, employing a finite difference method and discrete element method. This model takes into account predetermined cutting and caving ratios, as well as drawing intervals. To examine the caving process and roof particles, three different drawing sequences were examined: sequential drawing, segmented sequential drawing, and intermittent drawing. The findings suggest that, in terms of the reset shape of the drawing body before individual and entire caving, the segmented sequential drawing method exhibits noticeable drawbacks compared to the other two methods. From the perspective of the drawing weight, following “closing drawing opening when seeing gangue”, the sequential drawing, segmented sequential drawing, and intermittent drawing methods can yield 32.42 t, 26.87 t, and 35.78 t of top coal, with corresponding recovery rates of 73.39%, 60.81%, and 82.97%. Therefore, it can be concluded that intermittent drawing is suitable for implementation on LTCC working face 12,309.

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In situ investigations into overburden failures of a super-thick coal seam for longwall top coal caving

Cited by 83 publications

References 14 publications

Mechanism and Prevention of a Chock Support Failure in the Longwall Top-Coal Caving Faces: A Case Study in Datong Coalfield, China

Mechanism and Prevention of a Chock Support Failure in the Longwall Top-Coal Caving Faces: A Case Study in Datong Coalfield, China

Implementing FLAC3D model for simulating deformation mechanism of steel frame support set by actual profile

Optimization of drawing sequence in longwall top coal caving mining through an FDM‐DEM model

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