Mechanical mechanism of overlying strata breaking and development of fractured zone during close-distance coal seam group mining

Ning, Jianguo; Wang, Jun; Tan, Yunliang; Xu, Qiang

doi:10.1016/j.ijmst.2019.03.001

Cited by 116 publications

(53 citation statements)

References 1 publication

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“…Taking Ganhe Coal Mine as the engineering background, Wu et al [30] analyzed the mechanical model of silo wall and carried out dynamic analysis. Ning et al [31] studied the mechanical mechanism and development of overlying rock fragmentation in fracture zone in coal seam group mining. Yu et al [32] deduced the mechanical model of continuous failure of top coal based on damage mechanics and statistical strength theory.…”

Section: Introductionmentioning

confidence: 99%

Study on the Mechanical Characteristics of Surrounding Rock in Excavation

Zhang

Wei

2021

Mathematical Problems in Engineering

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Mine disasters, as associated problems in the development of coal resources, always threaten the life safety of miners and the production safety of enterprises. In coal roadway excavation, the coal in front of the excavation face is in a state of concentrated stress and the deformation is serious. The instability of the coal seam under stress is an important cause of the occurrence of coal and gas outburst. Thus, knowing the mechanical characteristics of surrounding rock in front of the working face is of great significance for deep understanding and effective prevention and control of coal-rock dynamic disasters. By analyzing the characteristics of stress evolution and deformation and failure in front of the heading face, the analytical solution of plastic region distribution in front of the heading face is obtained. According to the established mechanical model, MATLAB numerical calculation software is used to analyze different examples. The influence of different mechanical parameters on the stress state of the working face is studied. The influence parameters of the morphological characteristics of the plastic region are determined, and the change law and characteristics of the plastic region in front of the working face are studied. At the same time, through the characteristics of stress field, the working face dynamic risk assessment of coal and rock dynamic disaster can be realized, which can provide a powerful guarantee for the prevention and control of gas dynamic disasters in deep mine.

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Section: Introductionmentioning

confidence: 99%

Study on the Mechanical Characteristics of Surrounding Rock in Excavation

Zhang

Wei

2021

Mathematical Problems in Engineering

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“…These three kinds of propagation modes can be observed in relevant hydraulic fracturing tests and reservoir microseismic monitorization [17]. With the research deepening, some scholars carried out experiments on microcrack propagation mechanism and found that [18][19][20]; when the fracture approached the bedding plane, the disturbing stress field at the fracture tip would lead to the early failure of the bedding plane and form the microfracture zone, which was called Cooke-Garden cracking effect [21]. This early bedding plane fracture zone has a significant trapping effect on fracture propagation [22,23].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation on Hydraulic Fracture Propagation Law of Composite Rock Materials considering the Disturbing Stress Effect

Zhang

2021

Geofluids

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The stress disturbance effect will significantly affect the propagation path of hydraulic fractures in the composite rock reservoir. To reveal the influence mechanism of stress disturbance effect on the hydraulic fracture propagation, several groups of laboratory tests and simulation tests were carried out. The test results showed that the hydraulic fracture tip formed a disturbing stress field because of the pore water pressure. Before the hydraulic fracture was extended to the bedding plane, the bedding plane had been damaged under stress disturbance, and the disturbed fracture zone was formed. The propagation mode of hydraulic fracture at the bedding plane was highly sensitive to the formation of the disturbed fracture zone. The sensitivity is mainly reflected from two aspects. (1) Under the action of the hydraulic fracture tip disturbance stress, many microfractures are generated and penetrated into the disturbance fracture zone on the bedding plane. This behavior is accompanied by energy dissipation causing the bedding plane material to be significantly softened, and the energy required for hydraulic fracture propagation is reduced dramatically. (2) The formation of the disturbed fracture zone improves the degree of fragmentation of the bedding plane, and the permeability of the local area increases significantly, forming the dominant circulation path. The higher the development of the disturbed fracture zone, the greater the hydraulic fracture propagation tendency along the bedding plane. According to the formation characteristics of the bedding plane disturbed fracture zone, the author proposed a nonlinear fracture model of the bedding plane disturbed fracture zone and established the hydraulic fracture propagation path criterion. This paper further analyzed the influencing factors of the disturbed fracture zone’s formation conditions and found that the bedding plane’s cementation strength was the main factor affecting the development degree of the disturbed fracture zone.

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“…With the depletion of coal resources under suitable conditions, several coalmines have begun to mine close-distance coal seams [5,6]. Because of the short distance between adjacent coal seams, the upper coal seam affects the roof integrity of the lower coal seam after mining, and the remaining coal pillars of the upper coal seam can lead to stress concentration in the floor, thereby significantly impacting the stress environment of the lower coal seam [7,8]. A lower coal seam is typically more complicated and difficult to mine than a single coal seam [9].…”

Section: Introductionmentioning

confidence: 99%

Stability Analysis and Derived Control Measures for Rock Surrounding a Roadway in a Lower Coal Seam under Concentrated Stress of a Coal Pillar

Sun

Lü

et al. 2020

Shock and Vibration

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Numerical simulations have often been used in close-distance coal seam studies. However, numerical simulations can contain certain subjective and objective limitations, such as high randomness and excessively simplified models. In this study, close-distance coal seams were mechanically modeled based on the half-plane theory. An analytical solution of the floor stress distribution was derived and visualized using Mathematica software. The principal stress difference was regarded as a stability criterion for the rock surrounding the roadway. Then, the evolution laws of the floor principal stress difference under different factors that influence stability were further examined. Finally, stability control measures for the rock surrounding the roadway in the lower coal seam were proposed. The results indicated the following: (1) The principal stress difference of the floor considers the centerline of the upper coal pillar as a symmetry axis and transmits radially downward. The principal stress difference in the rock surrounding the roadway gradually decreases as the distance from the upper coal pillar increases and can be ranked in the following order: left rib > roof > right rib. (2) The minimum principal stress difference zones are located at the center of the left and right “spirals,” which are obliquely below the edge of the upper coal pillar. This is an ideal position for the lower coal seam roadway. (3) The shallowness of the roadway, a small stress concentration coefficient, high level of coal cohesion, large coal internal friction angle, and appropriate lengthening of the working face of the upper coal seam are conducive to the stability of the lower coal seam roadway. (4) Through bolt (cable) support, borehole pressure relief, and pregrouting measures, the roof-to-floor and rib-to-rib convergence of the 13313 return airway is significantly reduced, and the stability of the rock surrounding the roadway is substantially improved. This research provides a theoretical basis and field experience for stabilizing the lower coal seam roadways in close-distance coal seams.

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Mechanical mechanism of overlying strata breaking and development of fractured zone during close-distance coal seam group mining

Cited by 116 publications

References 1 publication

Study on the Mechanical Characteristics of Surrounding Rock in Excavation

Study on the Mechanical Characteristics of Surrounding Rock in Excavation

Experimental and Numerical Investigation on Hydraulic Fracture Propagation Law of Composite Rock Materials considering the Disturbing Stress Effect

Stability Analysis and Derived Control Measures for Rock Surrounding a Roadway in a Lower Coal Seam under Concentrated Stress of a Coal Pillar

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