Fracture Processes of Rock-Like Specimens Containing Nonpersistent Fissures under Uniaxial Compression

Chen, Miao; Yang, Shengqiang; Ranjith, P.G.; Yang, Wendong; Yin, Peng-Fei; Zhang, Yuanchao; Zhang, Qiangyong

doi:10.3390/en12010079

Cited by 43 publications

(18 citation statements)

References 46 publications

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“…The fragmentation degree was gradually alleviated from the gob side to the coal rib. Coalescent macroscopic fractures caused instability in the entry-surrounding rock [21]. Figure 8b reveals the microcosmic crack evolution pattern of the Figure 6 displays the final displacement map in the surrounding rock.…”

Section: Crack Evolution Analysismentioning

confidence: 99%

A Case Study on Optimization and Control Techniques for Entry Stability in Non-Pillar Longwall Mining

Yang

Wang

et al. 2019

Energies

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In order to reduce large deformation failure occurrences in non-pillar longwall mining entries due to roof weighting behaviors, a case study in Halagou coal mine was conducted on optimization and control techniques for entry stability in non-pillar longwall mining. The Universal Discrete Element Code (UDEC) modeling was adopted to study entry stability in non-pillar mining, and the characteristics of deformation and stress and crack propagation were revealed. The large deformation transmission between the entry-immediate roof and the gob-immediate roof could be eliminated by optimizing the entry roof structure through a directional roof-cutting method. The localized tensile stresses generated in the entry-surrounding rock caused the generation of coalescent macroscopic fractures, which resulted in the instability of the entry. The tensile stress state could be inhibited by an active flexible support system through enhancing the confining pressure on the surrounding rock. Serious rotation subsidence occurs in the entry roof due to periodic weighting of the main roof, which could be greatly reduced by a passive rigid support pattern. The numerical and field test results both showed that the roof weighting pressure was offloaded by the technique and that the deformation of the entry surrounding the rock in non-pillar mining was quite small. Thus, the technique can effectively ensure the stability of the gob-side entry, which can provide references for entry stability control in non-pillar longwall mining.

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Section: Crack Evolution Analysismentioning

confidence: 99%

A Case Study on Optimization and Control Techniques for Entry Stability in Non-Pillar Longwall Mining

Yang

Wang

et al. 2019

Energies

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“…Fractured rock masses (Figure 1(a)) are widely distributed in underground engineering due to geological action or excavation disturbance, which may bring serious safety hazard to the engineering stability [1][2][3][4]. Grouting is a useful way for controlling groundwater inrush and improving mechanical properties of fractured rocks in underground mining and engineering [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Cement Grout Nonlinear Flow Behavior through the Rough-Walled Fractures: An Experimental Study

Jin

Han

et al. 2020

Geofluids

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This research experimentally studied the effects of various fracture roughness (characterized by the fractal dimension D) and normal stress (normal loads FN) applied to fracture on ultrafine cement grout nonlinear flow behavior through rough-walled plexiglass fractured sample. A high-precision and effective sealing self-made apparatus was developed to perform the stress-dependent grout flow tests on the plexiglass sample containing rough-walled fracture (fracture apertures of arbitrary variation were created by high-strength springs and normal loads according to design requirements). The real-time data acquisition equipment and high-precision self-made electronic balance were developed to collect the real-time grouting pressure P and volumetric flow rate Q, respectively. At each D, the grouting pressure P ranged from 0 to 0.9 MPa, and the normal loads FN varied from 1124.3 to 1467.8 N. The experimental results show that (i) the Forchheimer equation was fitted very well to the results of grout nonlinear flow through rough-walled fractures. Besides, both nonlinear coefficient (a) and linear coefficient (b) in Forchheimer’s equation increased with increase of D and FN, and the larger the FN was, the larger the amplitude was. (ii) For normalized transmissivity, with the increase of Re, the decline of the T/T0−β curves mainly went through three stages: viscous regime, weak inertia regime, and finally strong inertia regime. For a certain D, as the normal load FN increased, the T/T0−β curves generally shifted downward, which shows good agreement with the single-phase flow test results conducted by Zimmerman. Moreover, with the increase of D, the Forchheimer coefficient β decreased. However, within smaller FN, β decreased gradually with increasing D and eventually approached constant values. (iii) At a given FN, Jc increased with increasing D.

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“…In engineering practice, various fault structures, joints and fissures of rock mass will cause local stress concentration. The process of initiation, expansion, overlap and penetration of these discontinuities is the main manifestation of rock mass instability and failure [21]. Therefore, the study of mechanical behavior of fractured rock mass under load and its signal monitoring are related to the stability and safety of the project.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emission Multi-Parameter Analysis of Dry and Saturated Sandstone with Cracks under Uniaxial Compression

Shen

et al. 2019

Energies

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In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone samples with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the samples start to crack earlier; the cracks grow slowly; the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure; more secondary cracks are produced. The saturated samples release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated samples release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the amplitude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.

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Fracture Processes of Rock-Like Specimens Containing Nonpersistent Fissures under Uniaxial Compression

Cited by 43 publications

References 46 publications

A Case Study on Optimization and Control Techniques for Entry Stability in Non-Pillar Longwall Mining

A Case Study on Optimization and Control Techniques for Entry Stability in Non-Pillar Longwall Mining

Cement Grout Nonlinear Flow Behavior through the Rough-Walled Fractures: An Experimental Study

Acoustic Emission Multi-Parameter Analysis of Dry and Saturated Sandstone with Cracks under Uniaxial Compression

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