Confined-Unconfined Changes above Longwall Coal Mining Due to Increases in Fracture Porosity

Booth, Colin J.

doi:10.2113/gseegeosci.13.4.355

Cited by 58 publications

(12 citation statements)

References 22 publications

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“…According to Equation (4), the roof subsidence function y i (x) involves the coal seam compression amount before mining. Thus, with the Equations (8) and (9), the roof subsidence amount U i (x) at the i th stage can be calculated as follows:…”

Section: Elastic Foundation Coefficientmentioning

confidence: 99%

“…This subsidence could extend up to the ground without any effective preventative measures, and therefore cause ground subsidence in an area larger than the mining range [5]. Since the ground subsidence due to underground mining could lead to buildings and farmlands being damaged [6][7][8], as well as water pollution and loss [9][10][11], it has been a worldwide problem and has generated widespread concerns in realms such as mining and environmental protection [5,12,13].…”

Section: Introductionmentioning

confidence: 99%

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

Zhang

2019

Energies

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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.

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Section: Elastic Foundation Coefficientmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Zhang

2019

Energies

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“…12 Colliery, a two-dimensional physical simulation was carried out to study the features of the overlying strata movement [20,21]. The geometry similarity of the physically similar simulation model is 1:100, the density similarity ratio is 1:1.67, and the time similarity ratio is 1:10.…”

Section: Length Ratio Effect Analysismentioning

confidence: 99%

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

et al. 2017

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Based on techniques of close upper protective coal-rock layer mining, relieved gas extraction, and underground gangue washing-discharging-backfilling, this paper initiates the concept of mixed fully-mechanized coal mining, which combines a solid backfilling method and a caving method (hereinafter referred to as "backfill and caving mixed mining"). After the principle and key techniques are introduced, a physical simulation experiment and a numerical simulation are used to study the characteristics of the overlying strata's fracture development, the main roof subsidence, the stress field and its influence area in the transition area with the length ratios of the backfilling section and the caving section, and the advancing distance of the mixed longwall face. Thus, the lengths of the caving section and the backfilling section, the parameters of the support system in the transition section, and the design process of the mixed longwall face are presented. In practice, the mixed longwall face Ji 15 -31010 in Ping-dingshan No. 12 Colliery proves that the designed lengths of 120 m and 100 m for the backfilling section and the caving section, respectively, are appropriate. The monitoring results of the hydraulic support working resistance show that the supports were working well in general; the maximum growth height of the overlying strata fracture is 18 m; the gas drainage efficiency is up to 80% and the average gas concentration is 0.1 g/m 3 ; a large quantity of gangue generated in the Ji 14 seam is disposed underground; coal and gas are extracted simultaneously; and significant environmental and economic benefits are realized.

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“…However, these studies have tended to emphasize a relationship between the water-conducting fractures and the position of the aquifers, focusing on aquifers within the scope of the fractured water-conducting zone rather than the areas outside [14,16]. Other hydrological responses from several case studies have been investigated [6,10,[17][18][19], and the impacts of deep mining on the overlying aquifers were assessed using various methods [19][20][21]. Although several studies were devoted to the influence of coal mining on groundwater, less attention has been given to strata failure and deformation.…”

Section: Introductionmentioning

confidence: 99%

Physical Simulation of Strata Failure and Its Impact on Overlying Unconsolidated Aquifer at Various Mining Depths

Zhang

Shi

et al. 2018

Water

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Underground mining severely lowers the water table and worsens the ecological environment. To determine the mechanism influencing drawdown in unconsolidated aquifers induced by deep mining combined with overburden movement, with a view to environmental protection, physical simulations for three different depths were designed to investigate and contrast deformation and fracture distribution characteristics at diverse depths after mining. The impacts on overlying unconsolidated aquifers were then analyzed by monitoring overburden movement and ground water level data, and the deformation limit was estimated. Modeling results indicated that coal mining had different impacts on the overlying unconsolidated aquifer via various mechanisms of groundwater level reduction. The aquifer outside the fractured water-conducting zone could be affected by coal mining, and the water tables dropped rapidly. The failure and the deformation features of the aquitard floor were the key to revealing the mechanism of groundwater depletion in deep mining. The effects on aquitard decreased as the distance from the working face increased. A relationship between the strata deformation and the drawdown rate was established; that is, the rate of decline of the groundwater level did not accelerate until the maximum subsidence of the aquitard floor exceeded approximately 0.9 m, or the subsidence-bending area of the aquitard floor exceeded approximately 156 m 2 .

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Confined-Unconfined Changes above Longwall Coal Mining Due to Increases in Fracture Porosity

Cited by 58 publications

References 22 publications

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

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

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

Physical Simulation of Strata Failure and Its Impact on Overlying Unconsolidated Aquifer at Various Mining Depths

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