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In order to reveal the mechanism of surrounding rock deformation and instability of soft rock roadway in 12# working face of Puhe coal mine, and synthetical analysis of the surrounding rock, deformation and failure of the roadway shows that the original support scheme is difficult to maintain the stability of roadway. Thus the basic concept of roadway surrounding rock control: Single anchor bolt form a compression zone to control the failure and expansion of surrounding rock, and a comparable number of anchor bolts form a homogeneous compression zone to inhibit the development of surrounding rock plastic zone. The "anchor blot + anchor cable net + concrete shotcrete support plan (arrangement of anchor cables four to five)" is proposed. Furthermore, and FLAC3d numerical simulation software was used to verify the rationality and reliability of the supporting scheme of "bolt + anchor cable net + concrete shotcrete support scheme (four to five anchor cables)" support scheme. The on-site monitoring results show that the soft rock roadway in Puhe Coal Mine 12# working face return airway passes through the "bolt + anchor cable net + concrete shotcrete support scheme (anchor cable four to five arrangement)" to reduce the surrounding rock deformation and become stable. The sinking amount of the roof and floor in the roadway is 251.2 mm, the convergence amount of the two sides in the roadway is 231 mm, supporting system and surrounding rock form the stable compression zone, the soft rock roadway can be effectively controlled by the support scheme, which can provide reference value for other similar engineering. [ABSTRACT FROM AUTHOR]

The mechanical model of the basic roof fracture structure is established on the basis of key block theory to study the roof breaking mechanism of gob-side entry retaining under roof cutting and pressure relief, and the analytical formula of roof support resistance is derived when the key block of the basic roof is stable. The influence of roof cutting angle and cutting height on roof support resistance is also analyzed. Determining the cutting seam parameters of the retained roadway roof is necessary to identify the support resistance of the roadway roof due to the correlation between the roof cutting parameters and the support resistance. Taking the II 632 haulage drift of the Hengyuan coal mine as the engineering background, FLAC3D numerical simulation is used in this paper to analyze the influence of different roof cutting angles and cutting heights on the surrounding rock structure evolution of retained roadways. Results show that the roof cutting angle and cutting height respond to the support resistance of the retained roadway roof, and the support resistance required by the roof increases with the roof cutting angle and cutting height. This condition ensures that the side roof of the gob can be cut off smoothly, and the support resistance required by the roof of retained roadways is within a reasonable range. Through theoretical and numerical simulation analysis, the reasonable roof cutting height of II 632 haulage drift is 8 m and the roof cutting angle is 15°. The theoretical analysis and numerical simulation results reveal that the required support resistance to maintain the stability of the roadway roof is 0.38 MPa. The supporting scheme of the roof of the II 632 haulage drift in the Hengyuan coal mine is then designed. Finally, the field industrial test is used for verification. The borehole imaging results show that the overall line of the retained roadway roof is small based on the description of field monitoring results. The deformation of the surrounding rock surface of the retained roadway is less than 100 mm, and the roadway is 40 m from the lagging working face. The deformation rate of surrounding rock decreases with the increase in distance from the working face. The integrity of the retained roadway roof is good, and the deformation of the surrounding rock is effectively controlled. [ABSTRACT FROM AUTHOR]

As the mining depth increases, the deformation of the roadway becomes more difficult to control. As a main supporting structure for maintaining the stability of roadway, the fully anchored bolt is widely used to reinforce deep mine. At the same time, the analysis of the stress distribution law of fully anchored bolt is the basic work to optimize anchor design. Therefore, this paper establishes a fully anchored bolt-surrounding rock interaction model based on the law of surrounding rock deformation and derives the analytical expressions for the axial force and shear stress of the fully anchored bolt during normal support and critical failure. At the same time, the effects of surrounding rock properties, support resistance, and bolt length on the stress distribution of fully anchored bolt are analyzed. The results show that the stress distribution of fully anchored bolt is consistent with the "neutral point" theory and the most important is the fact that the conditions of surrounding rock, the supporting resistance, and the length of bolt affect the actual stress distribution of the fully anchored bolt. It provides a certain theoretical basis for the design and development of anchoring and supporting technology. [ABSTRACT FROM AUTHOR]

To clarify the shear-slip process and characteristics of fault, we conducted triaxial shear tests driven by displacement on shale samples with prefabricated sawcut and natural fractures, and the acoustic emission (AE) technology was used to monitor the shear-slip process in real-time. According to the test results, the shear-slip process and mechanical characteristics of sawcut and natural fractures were analyzed. The test results indicate that the shear-slip process of fractures can be divided into four stages, improving the confining pressure will cause more serious plastic failure in the shear-slip process, and the increase of roughness will make the phenomenon of "stress drop" more obvious, which is closely related to the earthquake occurrence. Confining pressure and roughness all have implications for the stress thresholds of each stage. With the transition of shear-slip stages, the effects of confining pressure and roughness on the shear-slip of fractures are more drastic. The maximum static friction coefficient μ 0 increases with initial roughness increasing and is independent of confining pressure. Due to the strain-strengthening effect of fracture slip, the average value of dynamic friction coefficient μ d under simple shear deformation is greater than the maximum static friction coefficient μ 0. Based on AE response characteristics, microcracks development, and rupture scale during the shear-slip process were also explored. AE events are mainly distributed along the inclined fracture. The AE response in different shear-slip stages displays pronounced differences, and the AE evolution and macro mechanical characteristics of fractures show significant time-synchronization. The variation of peak frequency can reflect the rupture scale transformation and the influence of confining pressure and roughness. Additionally, the differences in the morphological evolution of sawcut and natural fractures are mainly reflected in the wear pattern, degree and the rock debris attach amount. Finally, we also discussed the micro-deformation mechanism of asperities during the shear-slip process. This work may provide a reference for the research of fault activation and slip in shale reservoirs. • Triaxial shear tests driven by displacement on shale samples with prefabricated sawcut and natural fractures were carried out. • Shear-slip process and acoustic emission (AE) evolution of sawcut and natural fractures in shale were analyzed. • Morphological evolution and characteristics of fracture surfaces before and after the test were revealed. • Micro-deformation mechanism of asperities during the shear-slip process was clarified. [ABSTRACT FROM AUTHOR]