Development Patterns of Fractured Water-Conducting Zones in Longwall Mining of Thick Coal Seams—A Case Study on Safe Mining Under the Zhuozhang River

Du, Feng; Gao, Rui

doi:10.3390/en10111856

Cited by 28 publications

(14 citation statements)

References 19 publications

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“…The method for determination used in the analysis, which was based on mechanical theories, was conservative and not capable of accurately calculating HWFZ in rock layers that have suffered damage, and the mechanistic model could not calculate HWFZ caused by the local failure of a stratum. The UDEC analytical software uses the discrete element method based on rock mechanical theories, as well as the lithology and parameters of the various strata; this method is thus capable of simulating the range of plastic damage in strata with a substantially high level of accuracy and overcoming the deficiencies of the HMP standard's predictive equation and mechanical calculation [38,39].…”

Section: Numerical Simulation Studies Of Hwfz In Sbmmentioning

confidence: 99%

Prediction of the Heights of the Water-Conducting Fracture Zone in the Overlying Strata of Shortwall Block Mining Beneath Aquifers in Western China

et al. 2018

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Longwall mining leaves pillars and irregular blocks of coal behind in its aftermath. In this study, a shortwall block mining (SBM) technique for recovering these coal resources has been proposed. A mechanical analysis model for calculating the heights of the water-conducting fracture zone (HWFZ) in overlying strata of SBM was established based on the theory of beams on elastic foundations. Using this model and the data acquired from a working face in the experimental area, a height of 50.30 m was calculated for HWFZ corresponding to this working face. This observation indicates that the equation for predicting HWFZ in working faces specified by the Hydrogeological Procedures for Mines (HPM) standard is not suitable for application in SBM. For this reason, the Universal Distinct Element Code (UDEC) modeling program was used to analyze the developmental behavior of the water-conducting fracture zone under various determining factors in SBM. The UDEC simulations indicated that the HWFZ increase linearly with an increase in mining height, decrease linearly with an increase in the width of the protective coal pillars, and increase logarithmically with block length. A nonlinear regression analysis of HWFZ was performed using the SPSS software suite, from which a model for predicting HWFZ in SBM was constructed. This model predicted that the HWFZ was 52.58 m in the experimental area, while field measurements yielded HWFZ values varying from 47.98 to 50.06 m, which was basically consistent with the results of the prediction model and the mechanical model, thus confirming the accuracy of the mechanical model and the reliability of the regression model. The results of this study will provide critical practical references for the enhancement of coal recovery rates in mining areas and enhance theories on aquifer protection during mining operations.

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Section: Numerical Simulation Studies Of Hwfz In Sbmmentioning

confidence: 99%

Prediction of the Heights of the Water-Conducting Fracture Zone in the Overlying Strata of Shortwall Block Mining Beneath Aquifers in Western China

et al. 2018

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“…Coal, the primary energy source in China, plays an important role in its economic development and energy security [1,2]. In 2019, the coal production was 3.85 billion tons and accounted for 57.7% of Chinese total energy consumption.…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al [16] adopted three methods to observe the height of a WCFZ, including borehole water leakage, borehole TV images, and numerical simulation. Methods that have been used to study the development law of the WCFZ include various numerical simulation methods, such as rock failure process analysis (RFPA) [17,18], Universal Distinct Element Code (UDEC) [1,19,20], Fast Lagrange Analysis of Continua (FLAC) [12], Particle Flow Code (PFC) [21], and the similar-material simulation method [22]. Also, borehole TV and an electrical logging drilling fluid loss observation system have been adopted to observe the height of the WCFZ.…”

Section: Introductionmentioning

confidence: 99%

Formation Mechanism and the Height of the Water‐Conducting Fractured Zone Induced by Middle Deep Coal Seam Mining in a Sandy Region: A Case Study from the Xiaobaodang Coal Mine

Xie

Hou

Wang

et al. 2021

Advances in Civil Engineering

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The height of the water-conducting fractured zone (WCFZ) is a basic parameter related to water protection in coal mines and is also crucial for aquifer protection and mine safety. In order to accurately detect the height and shape and reveal the formation mechanism of the WCFZ, which is caused by middle-deep coal seam mining in a sandy region, the 112201 coalface at the 1# coal mine of Xiaobaodang was taken as a case study. Filed measurements including fluid leakage, borehole TV, and similar simulation were adopted to analyze the regularity of the WCFZ in this area. The detection results of field measurements showed that the maximum height of the WCFZ was 177.07 m in a borehole near the open-off cut, and the ratio of the height of the water-conducting fractured zone divided by the mining thickness was 30.53. The WCFZ acquired an inward-convergent saddle shape, which was inclined to the goaf. The saddle bridge was located at the boundary of the goaf, and the saddle ridge was located at the center of the goaf. Also, through analyzing the results of similar simulations, we found that, in the process of mining, separation cracks and the beam structure were the main forms of overburden disturbance transmitting upward and ahead of mining, respectively. The main cause of the increase in height of the WCFZ was the connection of the separation cracks and vertical cracks caused by fractures of beam structures. The development of the WCFZ was divided into five stages: incubation stage, development stage, rapidly increasing stage, slowly increasing stage, and stable stage. Moreover, the duration of each stage was related to the lithology and mining technology. This research can provide significant theoretical insights for the prediction of the WCFZ, enabling the prevention of water hazards on mine roofs and assisting with water resources protection.

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“…The fissures (voids) in the former two zones interconnect with mine workings, forming water flow channels. Therefore, the fracture zone together with the caved zone has been defined as a fractured water-conducting zone [9,10], of which maximum height is often expressed and estimated as a function of the mining height in China [8][9][10][11]. It is generally known that, in a shallow coalfield, the fractured water-conducting zone intersects the overlying Quaternary aquifers, providing unhindered passageways for groundwater flow into the mining area.…”

Section: Introductionmentioning

confidence: 99%

“…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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Development Patterns of Fractured Water-Conducting Zones in Longwall Mining of Thick Coal Seams—A Case Study on Safe Mining Under the Zhuozhang River

Cited by 28 publications

References 19 publications

Prediction of the Heights of the Water-Conducting Fracture Zone in the Overlying Strata of Shortwall Block Mining Beneath Aquifers in Western China

Prediction of the Heights of the Water-Conducting Fracture Zone in the Overlying Strata of Shortwall Block Mining Beneath Aquifers in Western China

Formation Mechanism and the Height of the Water‐Conducting Fractured Zone Induced by Middle Deep Coal Seam Mining in a Sandy Region: A Case Study from the Xiaobaodang Coal Mine

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

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