scholarly journals Field and Numerical Modelling Investigations on the Stability of Underground Strata during Longwall Workings

2021 ◽  
Author(s):  
G Budi ◽  
Kolikipogu Nageswara Rao ◽  
Punit Mohanty
Keyword(s):  
Numerical Modelling ◽  
Longwall Mining ◽  
High Capacity ◽  
Field Monitoring ◽  
Longwall Face ◽  
Mining Method ◽  
Company Limited ◽  
Extensive Field ◽  
Powered Support ◽  
The Stability

Abstract Understanding the behaviour of underground workings is essential for the success of any mining method. The longwall mining method is one of the predominant underground methods to extract coal. Since 1978, in India, 22 underground coal mines of different collieries have been implemented the mechanized longwall method. SCCL is one of that colliery has mixed working experiences with longwall method in their mines. The longwall faces in GDK-10A, JK-5, and VK-7 of SCCL had produced good results, but the faces in GDK-7, GDK-9, GDK-11A, and PVK-5 had suffered due to the geological disturbances and unavailability of real-time information about the strata behaviour. By addressing the previous experiences of longwall workings, Singareni Collieries Company Limited (SCCL) has implemented a high capacity (1 × 1152T) powered support system in Adriyala Longwall Project (ALP) at a depth of 375m. In this study, extensive field monitoring with different strata monitoring instruments was conducted in ALP to analyze the gate roads convergence, stress variation on longwall and chain pillars at different stages of extraction (i.e., 8m, 25m, 35m, and 45m) and the pressure variation on the powered support systems. It was observed from the results that the convergence in the gate roads was increasing with the advance of the longwall face and the area of exposure. The pressure of the legs on the dip side was less than the pressure of the legs on the rise side, which implies a stable roof condition over the longwall face. To better understand the behaviour of ALP workings, a numerical modelling study with FLAC 7.0 has been conducted with actual physio-mechanical properties. The computed numerical modelling results have been remarkably well in consistent with the field monitoring results. The stability of chain pillars has been estimated at every stage of extraction by the Factor of Safety (FoS) criterion and it was found that the pillars could be ensured stability in longwall workings.

scholarly journals Comparative analysis of the mine pressure at non-pillar longwall mining by roof cutting and traditional longwall mining

2019 ◽  
Vol 16 (2) ◽  
pp. 423-438 ◽  
Author(s):  
Peng Zhou ◽  
Yajun Wang ◽  
Guolong Zhu ◽  
Yubing Gao
Keyword(s):  
Pressure Distribution ◽  
Coal Mining ◽  
Longwall Mining ◽  
Mining Industry ◽  
Mine Pressure ◽  
Mining Method ◽  
Working Face ◽  
Distribution Features ◽  
Mining Pressure ◽  
The Stability

Abstract Non-pillar coal mining has been developed and implemented in the recent decades in China's coal mining industry. The non-pillar longwall mining by roof cutting without pre-excavated entry (N00 mining method) is one of the latest non-pillar mining methods and this method has the advantages of reduced roadway drivage ratio and increased resource recovery ratio. Previous studies show that the mining pressure during the working face advancing is one of the main factors that affect the stability of underground structures and the safety production. However, there is no evaluation or analysis of the mining pressure at the mining face using entry retaining with roof pre-cutting and an absence of pre-excavated tail entry. In this paper, both field monitoring and numerical simulation approaches are employed in the analysis of the mining pressure distribution characteristics within a range of the whole working face during the face advancing. The results are compared with the field data and simulation results from the traditional mining method performed in the same coal mine. Results supported the idea that the N00 mining method can generate a low-stress area for the retained entry. The stability of the working face and retained entry can be well maintained due to the mine pressure optimization. This paper can aid in the understanding of structural mechanic modeling and mine pressure distribution features, structural mechanic analysis and mine pressure distribution features of the N00 mining method.

scholarly journals Characteristics of Roof Ground Subsidence While Applying a Continuous Excavation Continuous Backfill Method in Longwall Mining

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 95 ◽  
Author(s):  
Yihe Yu ◽  
Liqiang Ma ◽  
Dongsheng Zhang
Keyword(s):  
Longwall Mining ◽  
Beam Theory ◽  
Horizontal Displacement ◽  
Ground Subsidence ◽  
Mining Method ◽  
Control Effect ◽  
Room And Pillar Mining ◽  
Site Monitoring ◽  
Coal Pillars ◽  
The Stability

Activities of traditional longwall mining will result in ground subsidence and therefore cause issues such as damages to buildings and farmlands, water pollution and loss, and potential ecological and environmental problems in the mining region. With advantages of the longwall backfill mining method, as well as the room and pillar mining method, a continuous excavation and continuous backfill (CECB) method in longwall mining is recommended to effectively control the ground subsidence. In this method, mining roadways (MRs) are initially planned in a panel, and then they are excavated and backfilled in several stages until the whole panel is mined out and backfilled. According to the geologic conditions of an underground coal mine, and the elastic foundation beam theory, a mechanical model was built to study the subsidence of the roof while using this new mining method. In addition, methods to calculate roof subsidence in various stages in CECB were also provided. The mechanical parameters of backfilling materials, which were used in the theoretical calculation and the numerical analysis for mutual check, were defined through analyzing the stability conditions of the coal pillars and the filling bodies. The control effect for the ground subsidence of using the newly proposed mining method was analyzed based on both simulation results and site monitoring results, including the ground subsidence, horizontal displacement, tilt, curvature and horizontal strain. This research could provide suggestions to effectively control ground subsidence for a mine site with similar geologic conditions.

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

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Phu Minh Vuong Nguyen ◽  
Tomasz Olczak ◽  
Sywester Rajwa
Keyword(s):  
Numerical Modelling ◽  
Failure Modes ◽  
Longwall Mining ◽  
Underground Mining ◽  
Copper Deposit ◽  
Ore Deposits ◽  
Mining Method ◽  
Copper Mine ◽  
3D Numerical Modelling

Abstract 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.

scholarly journals Measurement of xylem water pressure using High-Capacity Tensiometer and benchmarking against Pressure Chamber and Thermocouple Psychrometer

2020 ◽  
Vol 195 ◽  
pp. 03014
Author(s):  
Roberta Dainese ◽  
Giuseppe Tedeschi ◽  
Thierry Fourcaud ◽  
Alessandro Tarantino
Keyword(s):  
Water Flow ◽  
Water Pressure ◽  
High Capacity ◽  
Ground Surface ◽  
Pressure Chamber ◽  
Rainwater Infiltration ◽  
Thermocouple Psychrometer ◽  
Earth Structures ◽  
Pressure Water ◽  
The Stability

The response of the shallow portion of the ground (vadose zone) and of earth structures is affected by the interaction with the atmosphere. Rainwater infiltration and evapotranspiration affect the stability of man-made and natural slopes and cause shallow foundations and embankments to settle and heave. Very frequently, the ground surface is covered by vegetation and, as a result, transpiration plays a major role in ground-atmosphere interaction. The soil, the plant, and the atmosphere form a continuous hydraulic system, which is referred to as Soil-Plant-Atmosphere Continuum (SPAC). The SPAC actually represents the ‘boundary condition’ of the geotechnical water flow problem. Water flow in soil and plant takes place because of gradients in hydraulic head triggered by the negative water pressure (water tension) generated in the leaf stomata. To study the response of the SPAC, (negative) water pressure needs to be measured not only in the soil but also in the plant. The paper presents a novel technique to measure the xylem water pressure based on the use of the High-Capacity Tensiometer (HCT), which is benchmarked against conventional techniques for xylem water pressure measurements, i.e. the Pressure Chamber (PC) and the Thermocouple Psychrometer (TP).

Prospects for the development of underground ore mining geotechnologies at the Talnakh and Oktyabrskoye deep mines

2021 ◽  
pp. 70-75
Author(s):  
I.I. Aynbinder ◽  
P.G. Patskevich ◽  
O.V. Ovcharenko
Keyword(s):  
High Capacity ◽  
Underground Mines ◽  
Total Production ◽  
Stress Concentrations ◽  
Mining System ◽  
Sulphide Ore ◽  
Rock Mass Deformation ◽  
The Rich ◽  
Context Mining ◽  
The Stability

Rich sulphide, cuprous and impregnated ores are currently mined in the underground mines of the Talnakh and Oktyabrskoye deposits at the depths from 250 to 1,700 m. The reserves of rich ores are depleted, and therefore the growth of cuprous and impregnated ores is gaining importance. Their share may reach 80% of the total production by 2030. A distinctive feature of such deposits is the occurrence of cuprous and impregnated ores above the rich sulphide ore, which reserves have been mined out using mining systems with curing backfill mixtures. In this context, mining of impregnated ores will be done in the undermined zones, which will lead to significant rock mass deformation, opening of existing natural and formation of new cracks, will affect the stability of mining structures and will require special measures to control rock pressure in the mines. The paper presents the results of assessing the stress-and-strain condition of the undermined mass of impregnated ores mined using the room-and-pillar cut-and-fill method at the depths of 500, 1000 and 2000 m. The assessment shows that no dangerous stress concentrations arise in the mining structures at great depths which creates preconditions for the safe development of such deposits. A significant increase in ore extraction will require upgrading of existing underground facilities. It is proposed to carry out pre-concentration of the mined ore in the underground conditions using modern crushing complexes, high-capacity mine separators to remove waste rock, which can subsequently be used as the backfill material. In this way, a closed-loop mining system is created that meets the efficiency requirements of mining production and integrated subsoil development.

scholarly journals Study on the Fracture Law of Inclined Hard Roof and Surrounding Rock Control of Mining Roadway in Longwall Mining Face

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5344
Author(s):  
Feng Cui ◽  
Shuai Dong ◽  
Xingping Lai ◽  
Jianqiang Chen ◽  
Chong Jia ◽  
...  
Keyword(s):  
Energy Release ◽  
Longwall Mining ◽  
Coal Pillar ◽  
High Energy ◽  
Mechanical Analysis ◽  
Engineering Practice ◽  
Analysis Model ◽  
Hard Roof ◽  
Working Face ◽  
The Stability

In the inclination direction, the fracture law of a longwall face roof is very important for roadway control. Based on the W1123 working face mining of Kuangou coal mine, the roof structure, stress and energy characteristics of W1123 were studied by using mechanical analysis, model testing and engineering practice. The results show that when the width of W1123 is less than 162 m, the roof forms a rock beam structure in the inclined direction, the floor pressure is lower, the energy and frequency of microseismic (MS) events are at a low level, and the stability of the section coal pillar is better. When the width of W1123 increases to 172 m, the roof breaks along the inclined direction, forming a double-hinged structure, the floor pressure is increased, and the frequency and energy of MS events also increases. The roof gathers elastic energy release, and combined with the MS energy release speed it can be considered that the stability of the section coal pillar is better. As the width of W1123 increases to 184 m, the roof in the inclined direction breaks again, forming a multi-hinged stress arch structure, and the floor pressure increases again. MS high-energy events occur frequently, and are not conducive to the stability of the section coal pillar. Finally, through engineering practice we verified the stability of the section coal pillar when the width of W1123 was 172 m, which provides a basis for determining the width of the working face and section coal pillar under similar conditions.

scholarly journals Calculation of Residual Surface Subsidence Above Abandoned Longwall Coal Mining

2020 ◽  
Vol 12 (4) ◽  
pp. 1528 ◽  
Author(s):  
Ximin Cui ◽  
Yuling Zhao ◽  
Guorui Wang ◽  
Bing Zhang ◽  
Chunyi Li
Keyword(s):  
Coal Mining ◽  
Longwall Mining ◽  
Land Reclamation ◽  
Surface Subsidence ◽  
Mining Subsidence ◽  
First Year ◽  
Longwall Coal Mining ◽  
The Stability ◽  
Ecological Reconstruction

Exhausted or abandoned underground longwall mining may lead to long-term residual subsidence on surface land, which can cause some problems when the mined-out land is used for construction, land reclamation and ecological reconstruction. Thus, it is important to assess the stability and suitability of the land with a consideration of residual surface subsidence. Assuming a linear monotonic decrease in the annual residual surface subsidence, the limit of the sum of the annual residual subsidence factor, and continuity between surface subsidence in the last year of the weakening period and the residual surface subsidence in the first year, we establish a model to calculate the duration of residual subsidence and the annual residual surface subsidence factor caused by abandoned longwall coal mining. The duration of residual surface subsidence increases with the increase in mining thickness as well as the factor of extreme residual subsidence. The proposed method can quantitatively calculate the annual residual subsidence, the accumulative residual subsidence, and the potential future accumulative residual subsidence. This approach can be used to reasonably evaluate the stability and suitability of old mining subsidence areas and will be beneficial for the design of mining subsidence land reclamation and ecological reconstruction.

scholarly journals Mechanisms behind strong strata behaviour in high longwall mining face-ends under shallow covers

2019 ◽  
Vol 16 (3) ◽  
pp. 559-570 ◽  
Author(s):  
Weibing Zhu ◽  
Xiangrui Qi ◽  
Jinfeng Ju ◽  
Jingmin Xu
Keyword(s):  
Longwall Mining ◽  
Coal Pillar ◽  
Field Measurements ◽  
Main Roof ◽  
Longwall Face ◽  
Effective Control ◽  
Coal Seams ◽  
Roof Collapse ◽  
Coal Pillars ◽  
Roadway Deformation

Abstract Safe and efficient mining of shallow coal seams relies on the understanding and effective control of strata behaviour. Field measurements, theoretical analysis and numerical simulations are presented in this study to investigate the mechanism behind abnormal strata behaviour, such as roof collapse and severe roadway deformation, that occurs in high longwall face-ends under shallow cover. We observed that coal pillars with two sides being mined out become unstable when the cover depth exceeds a certain value. The instability of the coal pillar can alter the fracture line of the overlying strata, triggering a reversed rotation of the ‘curved triangle blocks’ that form after the breakage of the overlying main roof. The revolving blocks apply stress on the roof strata directly above the longwall face-end, resulting in roof collapse. The collapse of both the coal pillars and the roof also leads to the advancement and increase of the overlying abutment pressure, which further causes severe roadway deformation in front of the working face. The strong strata behaviour that occurs in high longwall face-ends with shallow cover is presented in this study and countermeasures are proposed, such as widening or strengthening the coal pillar, or implementing destress blasting. The countermeasures we proposed and the results of our analyses may facilitate the safe mining of shallow coal seams with similar problems in the future, and may improve the safety and efficient working of coal mines.

Numerical modelling of rainfall effects on the stability of soil slopes

2017 ◽  
Vol 13 (5) ◽  
pp. 425-437 ◽  
Author(s):  
Adarsh S. Chatra ◽  
G. R. Dodagoudar ◽  
V. B. Maji
Keyword(s):  
Numerical Modelling ◽  
Soil Slopes ◽  
The Stability
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