Target Stratum Determination of Surface Hydraulic Fracturing for Far-Field Hard Roof Control in Underground Extra-Thick Coal Extraction: A Case Study

Lu, Yiyu; Gong, Taorong; Xia, Binwei; Yu, Bin; Huang, Fei

doi:10.1007/s00603-018-1616-9

Cited by 52 publications

(23 citation statements)

References 14 publications

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“…The cave-in zone height is calculated as the product of the caved roof thickness and the bulk factor. 6 In order to calculate the hydraulic support load numerically, a support element at the bottom corner of the working face is generated to approximately model the mechanical behavior of the hydraulic power support. 51 According to the elasto-plasticity theory, a special module was developed to calculate the released energy.…”

Section: Numerical Simulation For Etcsmmentioning

confidence: 99%

“…51 According to the elasto-plasticity theory, a special module was developed to calculate the released energy. 6 This model is 1,600 m long and 540 meters high, and it consists of units 52 890. On the upper part of the model, the free boundary is adopted, and the lower part of fixed boundary controlled in horizontal displacement.…”

Section: Numerical Simulation For Etcsmmentioning

confidence: 99%

“…[3][4][5] These hazards represent a severe danger to safe production and pose a new challenge to achieving hard roof control in ETCSM. [6][7][8][9] According to incomplete statistics, up to 132 SGP activities (the shrinkage of the support pillar exceeding 600 mm) have been recorded in Tashan and Tongxin coal mines since the ETCSM in 2008, of which approximately 21 frame-pressing accidents occurred in stopes. These problems are not unique in China, and have been reported in India and the USA.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Pan

Xia

et al. 2020

Energy Science & Engineering

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Traditional methods of controlling hard roofs have a limited scope of action and cannot effectively release the strong ground pressure behavior (SGPB) induced by high-position hard roofs (HHRs) in extra-thick coal seam mining (ETCSM). Thus, an innovative control technology of fracturing HHRs by vertical-well stratified fracturing (VWSF) has been proposed. However, the key parameters of VWSF, namely fracturing horizon and fracturing thickness of HHRs, which have a significant influence on stope stability, remain uncertain. In this study, a mechanical model of the "coal wall-hydraulic support-gangue" support system is established by considering the effective loading acting on HHRs, through which modified expressions for the periodic breaking span and impact kinetic energy of the stope are deduced. Based on the self-bearing of bulking rocks, the stability principle of the surrounding rock, and energy dissipation theories, the criteria for determining the fracturing horizon and thickness of the HHR are obtained. Next, a numerical model of ETCSM, which accounts for the supporting effect of gangue, is constructed in FLAC3D. The support load and energy released by stratum breakage are determined through modeling under various hard roof parameters, thus verifying the correctness of the determination criteria. The results show that the energy released by a hard roof, average support load, and critical support load are positively correlated with thickness, and first increase before declining with respect to an increase in the fracturing horizon.The key parameters for a real coal mine are obtained by theoretical calculations and numerical simulations. A field application demonstrates that the support load and advance roadway deformation can be decreased using the proposed parameterization. This provides theoretical support for determining the key parameters of HHRs for VWSF and facilitates the widespread application of VWSF technology in HHR control. K E Y W O R D Shigh-position hard roofs, microseismic monitoring, mine safety, strong ground pressure behavior, vertical-well stratified fracturing | 2217 PAN et Al.

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Section: Numerical Simulation For Etcsmmentioning

confidence: 99%

Section: Numerical Simulation For Etcsmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Pan

Xia

et al. 2020

Energy Science & Engineering

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“…The key roof strata significantly influence the movement of the overlying strata and its sudden failure may lead to violent impact on mine space. Lu et al (2019) report the use of a surface hydraulic fracturing technique to crack the far-field hard roof strata when mining extra-thick coal seams of 20 m average thickness. The target stratum for fracturing is estimated by comparing the cracking energy release of the different roof strata based on numerical simulations.…”

Section: The Special Issuementioning

confidence: 99%

Introduction to the Special Issue “Rock Mechanics Advances in China Coal Mining”

Zhang

Barla

2019

Rock Mech Rock Eng

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“…Professor Yu proposed the method and applied it in the eld for the rst time, achieving an excellent control effect (Yu et al2019). Aimed at the selection of the target layers for ground fracturing, Binwei Xia compared and analyzed the breaking strength of hard roofs at different levels and determined the reasonable range of ground fracturing layers via numerical simulation (Lu et al 2018). Regarding the ground pressure control mechanism and in uence on the strata structural morphology of ground fracturing, scholars have not conducted in-depth research.…”

Section: Introductionmentioning

confidence: 99%

Study on Mine Pressure Control by Ground Fracturing High-level Hard Rock Strata

Gao

Kuang²,

Zhang³

et al. 2020

Preprint

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During extra-thick coal seam mining, the high-level thick and hard strata are the main reason for the presence of a strong ground pressure in the working face; however, there is no active and effective control technology for high-level hard strata. This paper proposes the concept of ground fracturing hard roofs, and the physical simulation was used to study the control effect of ground fracturing on the strata breaking structure and energy release. The results showed that the ground fracturing changed the structural characteristics of the strata and reduced the energy release intensity and overburden movement spatial extent, which had a significant control effect on the ground pressure. The Datong mining area was selected as the engineering background, a ground horizontal well fracturing engineering test was conducted on site, and a 20-m-thick hard rock layer, which was 110 m vertically away from the coal seam, was determined as the fracturing target layer. On-site microseismic monitoring showed that the crack propagation length was up to 216 m, and the height was up to 50 m. On-site mine pressure monitoring showed that the roadway deformation was reduced to 100 mm, the periodic weighting characteristics of the hydraulic supports were not obvious, the ground pressure in the working face was significantly controlled, and the ground fracturing was successful. Ground fracturing changed the occurrence characteristics of the high-level hard strata, which is beneficial to ameliorate the stress environment of a working face and provide a new approach of hard rock control.

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Target Stratum Determination of Surface Hydraulic Fracturing for Far-Field Hard Roof Control in Underground Extra-Thick Coal Extraction: A Case Study

Cited by 52 publications

References 14 publications

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Introduction to the Special Issue “Rock Mechanics Advances in China Coal Mining”

Study on Mine Pressure Control by Ground Fracturing High-level Hard Rock Strata

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