Parametric Analysis of Slotting Operation Induced Failure Zones to Stimulate Low Permeability Coal Seams

Si, Guangyao; Durucan, Şevket; Shi, Ji‐Quan; Korre, Anna; Cao, Wenzhuo

doi:10.1007/s00603-018-1579-x

Cited by 48 publications

(18 citation statements)

References 26 publications

(30 reference statements)

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“…We use the strain‐softening Mohr‐Coulomb model to quantify the peak and the postpeak properties of the rocks. As being documented in many studies, this model is characterized by the cohesion and friction angle for peak strengths and by the alternation of both properties for the postpeak behavior. The difficulty of using this model lies in quantifying the relations between rock properties (cohesion and friction angle) and the accumulation of the plastic strains .…”

Section: Laboratory Tests and Development Of The Numerical Modelmentioning

confidence: 99%

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Depressurizing boreholes for mitigating large deformation of the main entry

Wang

Zheng

Shen

et al. 2019

Energy Science & Engineering

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The main entries in longwall coal mine frequently encounter large deformation, depending on the stress environment. Depressurizing boreholes are applicable to reduce the large deformation; however, it is difficult to determine the proper parameters (diameter and spacing) for an effective implementation. This study aims to propose feasible design criteria for the quantification of those parameters. We first developed a rigorous numerical model, for a roadway in Zhangshuanglou coal mine, using the rock mechanical properties determined from extensive laboratory measurements and analyses. We then investigated the dependency of the stress transfer and roadway deformation on the ratio of borehole diameter and spacing (D/R and D/I). The symbols of D, R, and I represented the diameter, row spacing, and interspacing of the boreholes, respectively. We found that (a) D/R has to be between 1:6 and 1:2; and (b) D/I has to be between 1:6 and 1:4, for sufficient depressurization in the surrounding rocks. The optimized borehole diameter and spacing parameters were applied in the field where the deformation of roadway was significantly reduced. Finally, we proposed a criterion to determine those parameters of depressurization boreholes for application in other geological and mining conditions.

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Section: Laboratory Tests and Development Of The Numerical Modelmentioning

confidence: 99%

“…The difficulty of using this model lies in quantifying the relations between rock properties (cohesion and friction angle) and the accumulation of the plastic strains. 28,29 In this section, the following four steps were carried out to reveal the postpeak properties of rocks.…”

Section: Strengths Of the Rock Massesmentioning

confidence: 99%

Depressurizing boreholes for mitigating large deformation of the main entry

Wang

Zheng

Shen

et al. 2019

Energy Science & Engineering

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“…Wei [31] simulated the formation of the stress relief area by hydraulic slotting utilizing PFC2D software and concluded that the effective slotting radius of the coal seam was 0.5 m and optimal hole spacing was 5 m. Lu et al [32] pointed out that, in the same seam, the optimal distance between the slots is 4 m. Zhang and Zou [33] and Cheng et al [34] established the prediction model of slotting depth and verified its precision in the field test. Si et al [35] discussed the influence of geological mechanical property, in situ stress, slotting shape, slotting spacing, and other key parameters on slotting performance. Lu et al [36,37] studied the influence of slotting parameters on fracture closure of soft and hard coal after slotting.…”

Section: Introductionmentioning

confidence: 99%

Stress Relief and Stimulation of Coal Reservoir by Hydraulic Slotting

Cheng

Zhang

et al. 2021

Advances in Civil Engineering

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Coal seam permeability is one of the key factors influencing the gas extraction efficiency, which is of great significance to reduce coal and gas dynamic disasters in gassy coal mines. Hydraulic slotting technique is an effective method to stimulate the coal reservoir, but the selection of slotting key parameters has great impact on gas extraction efficiency. For this reason, the hydraulic slotting model was established by using FLAC3D software to analyze the stress distribution before and after slotting. Then, the influence of borehole diameter, slotting width, and slotting length on coal seam stress relief is also discussed. The results show that the slotting width has a great influence on the stress relief of the coal seam, while the borehole diameter and slotting length have no obvious influence on that. Based on the results of numerical simulation, field tests were carried out in Sangshuping NO.2 coal mine. The results show that the coal seam stress can be fully released, resulting in the improvement of coal seam permeability. The gas extraction efficiency can be highly enhanced by hydraulic slotting. This research achievement provides the guidance basis for high-stress water jet slotting technology with adaptive selection of slotting parameters in different geological conditions.

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“…Liu et al established a theoretical constitutive model for damage of coal seam with hydraulic slotting. Si et al and Li et al have studied the variation of stress distribution around the borehole of hydraulic slotting borehole and determined the basic parameters of the hydraulic slotting. Zhang et al have analyzed the strain‐softening behavior of coal around hydraulic slotting borehole and the influence of coal failure on permeability.…”

Section: Introductionmentioning

confidence: 99%

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Qin

Wei

Lou

et al. 2020

Energy Science & Engineering

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Predrainage of gas by cross‐boreholes is an important method to prevent coal and gas outbursts in the process of a coal roadway excavation. Limitations of technologies and poor effects of preventing coal and gas outbursts occur in the coal seam with a soft layer. In this study, a new hydraulic caving technology for cross‐boreholes has been proposed to solve this problem. A CT equipment was used to observe the development of coal fissures around cross‐boreholes in the coal seam with a soft layer. The plastic zone range and permeability distribution of ordinary hydraulic slotting technologies and the new hydraulic caving technology also were compared by numerical simulation. The field test of hydraulic caving was taken in the Xuehu Mine (China). The results show that the fracture development degree of soft coal is greater than that of hard coal at the same distance from cross‐boreholes. The fracture development degree in the plastic zone is greater than that in the elastic zone. The hydraulic caving technique can achieve the same effect as the ordinary hydraulic slotting with less workload. The mass of coal discharged from a cross‐borehole was 1.15 t/m and the average methane concentration of single drainage borehole increased by 1.09‐4.1 times, and the average methane extraction amount of single drainage borehole increased by 6.06 times. Elimination of coal and gas outburst had been completed after 110 days of extraction in the area of hydraulic caving, and Q and S values are lower than the critical value during roadway excavation. It is conclusion that hydraulic caving technique can effectively improve the permeability and rapidly eliminate coal and gas outburst in the coal seam with a soft layer.

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Parametric Analysis of Slotting Operation Induced Failure Zones to Stimulate Low Permeability Coal Seams

Cited by 48 publications

References 26 publications

Depressurizing boreholes for mitigating large deformation of the main entry

Depressurizing boreholes for mitigating large deformation of the main entry

Stress Relief and Stimulation of Coal Reservoir by Hydraulic Slotting

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

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