Fracture Development at Laminated Floor Layers Under Longwall Face in Deep Coal Mining

Li, Chunyuan; Zuo, Jianping; Wei, Chunchen; Xu, Xiang; Zhou, Ziqi; Yang, Li; Zhang, Yong

doi:10.1007/s11053-020-09684-6

Cited by 24 publications

(8 citation statements)

References 27 publications

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“…Floor failure in coal mining will form a plastic-yield zone, unloading-failure zone, unloading-expansion zone, gangue-damage zone, and pre-peak-damage zone [24]. Combined with the near-field rock-strata control theory [34][35][36], it can be determined that the masonry-beam structure can easily be formed at the end of a working face after basic roof failure. Therefore, the floor-failure characteristics of the inclined goaf roadway in deep mining at all stages are shown in Figure 7.…”

Section: Stress Environment and Floor Asymmetric-failure Characterist...mentioning

confidence: 99%

Mechanism and Control of Asymmetric Floor Heave in Deep Roadway Disturbed by Roof Fracture

Wei

Zhang

et al. 2023

Sustainability

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In view of the serious problem of bottom-drum damage in deep mining along empty roadways, the asymmetric bottom-drum damage characteristics and control mechanisms of deep mining along an empty roadway were studied using the trackway of the 11060 working face in Zhao Gu II mine as the research background. Based on the slip-line theory, support-pressure distribution law, and Griffith’s damage-criterion theory, the mechanism of asymmetric bottom drums and the maximum fracture-development depth of the bottom plate in a deep roadway under top-plate fracture perturbation were analyzed. The 3DEC discrete-element software was used to simulate and analyze the characteristics and evolution of the asymmetric bottom bulge of the roadway under dynamic-load disturbance, and the asymmetric control scheme of “slurry anchor reinforcement + top cutting and pressure relief” was proposed. The results show that, under the influence of static load of deep high-abutment pressure and the dynamic-load impact of the instability of the masonry-beam structure under periodic pressure of the adjacent working face, the deep-mining goaf roadway was prone to producing asymmetric floor heave. The floor-heave degree and maximum fracture-development range of the roadway in the affected area under the influence of dynamic load > those in goaf roadway > those in the roadway in the stable area affected by tunneling. The distribution of stress, displacement, and maximum floor heave was skewed to the side of the coal pillar in the goaf, showing an inverted right oblique V shape. The asymmetric floor heave of a roadway can be effectively controlled by grouting anchor-cable reinforcement (increasing the anti-damage limit) and roof-cutting pressure relief (cutting off the dynamic-load source). The research results can provide an important reference for the control of roadway floors under similar geological conditions.

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Section: Stress Environment and Floor Asymmetric-failure Characterist...mentioning

confidence: 99%

Mechanism and Control of Asymmetric Floor Heave in Deep Roadway Disturbed by Roof Fracture

Wei

Zhang

et al. 2023

Sustainability

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“…Particularly sensitive to water is claystone, which after just a few hours of water exposure show a large decrease in strength, loss of cohesion, and transforms into a plump mass with partial or complete loss of bearing capacity [11,37]. Along with the water absorption of the rocks, their volume density changes, which in the case of roof and sidewall layers will increase the load on both the support of an excavation and its floor, which may again increase the upheaval value [11,38]. The water contained in the rock pores creates a pore pressure, which reduces the friction on the surface of the cracks formed in the rock, which results in a much faster development of the fractures system in the rocks, reduced strength, and increased deformability [21,37,39,40].…”

Section: The Mechanism Of the Floor Upheaval In Roadwaysmentioning

confidence: 99%

The Effect of Selected Factors on Floor Upheaval in Roadways—In Situ Testing

2020

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The phenomenon of the floor upheaval occurs in virtually every type of rock mass and at every depth, accompanying the process of excavation of tunnels and headings. Despite its inconvenience, it is rarely studied because of the complexity of the process and the multiplicity of the factors causing deformations in floor rocks. To quantify the effect of the selected factors on floor upheaval, this article presents an analysis of results of in situ measurements carried out in three coal mine roadways at 15 measuring stations. These measurements were taken over varying periods of time, between 129 and 758 days. Groundwater and fault zones intersecting the excavations were considered as the key factors that affect floor upheavals. Therefore, the measurement bases were located at local faults and sites of water inflow. To compare the results, the stations were also located where the rock mass was not exposed to any factors other than stresses resulting from the depth of the excavation. The excavations were driven in various rocks and were located at different depths from 750 to 1010 m. The analyses of the study results show that the floor upheaval always depends on time and can be described in polynomial form: ufl = a·t2 + b·t + c or by a power function: ufl = a·tb. However, the further regression analyses show that roadway’s floor upheaval can be expressed by a complex form using the key parameters determining the phenomena. In the absence of an impact of geological factors on the stability of the excavation, the floor upheaval depends on floor rocks compressive strength σc and Young’s modulus E: ln(ufl)=a·ln(tσc)−bE−c; in the case of rock mass condition affected by water depends on the rock compressive strength reduction after submerging rock in water σcs 6h: ufl=a·t0.5−bσcs 6hσc+c and in the case of fault depends on the fault’s throw f: ufl=a·t0.8+b·f1.2−c. Statistical analysis has shown that the matching of the models to the measurement data is high and amounts to r = 0.841–0.895. Hence, in general, the analysis shows that the floor upheaval in underground excavation in any geological conditions may grow indefinitely.

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“…Vladyslav et al 22 carried out bending load failure test on prefabricated fissured granite, and found that the changing characteristics of rock fracture energy and peak load increase with the increase of eccentricity. Li et al 23 carried out the loading and unloading fracture test of red sandstone and found the linear energy storage and consumption characteristics in the process of rock tensile failure. Pinazzi et al 24 conducted bending load fracture test on mudstone and sandstone, and found that the rock fracture energy increased with the increase of loading rate.…”

Section: Introductionmentioning

confidence: 99%

Study on the evolutionary characteristics of strain energy on crack propagation in coal and rock under bending load

Zhang,

Gong

et al. 2024

Energy Science & Engineering

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The failure of coal mine overburden is mainly caused by fractures under bending loads. The energy evolution characteristics of coal and rock fractures are closely related to coal mine disasters such as rock burst. To obtain the characteristics of energy release and accumulation of coal and rock under bending load, three‐point bending tests of coal, mudstone, and sandstone were carried out respectively. The strength characteristics and fracture propagation process of coal and rock under bending load were studied. The strain energy evolution rules of coal and rock were calculated and obtained. The fracture mechanism of coal and rock was discussed by analyzing the critical strain energy release rate. The results show that the fracture complexity of sandstone and mudstone is greater than that of coal. The microstructure and its directivity in coal and rock indirectly affect their fracture characteristics through the elastic modulus characteristics. The distribution of parameters such as peak load of fracture, fracture energy, and crack length of coal and mudstone samples is discrete, while that of sandstone samples is concentrated. The deformation energy density of coal and rock basically shows a linear increase trend at the prepeak stage. The deformation energy density evolution characteristics at the postpeak stage are mainly affected by the load drop. It is important to establish the internal relationship between the meso structural characteristics and macro mechanical properties for solving engineering problems.

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Fracture Development at Laminated Floor Layers Under Longwall Face in Deep Coal Mining

Cited by 24 publications

References 27 publications

Mechanism and Control of Asymmetric Floor Heave in Deep Roadway Disturbed by Roof Fracture

Mechanism and Control of Asymmetric Floor Heave in Deep Roadway Disturbed by Roof Fracture

The Effect of Selected Factors on Floor Upheaval in Roadways—In Situ Testing

Study on the evolutionary characteristics of strain energy on crack propagation in coal and rock under bending load

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