Mine pressure regularity of working across over roadway and control effect analysis

Analyzed roof rock layer structure and rock layer thickness of -550 level west main roadway and proposed that the stability of calcareous rock layer was the premise of mining successfully. According to different roof condition and rock pillar size of main roadway, different reinforcement plans were used to strengthen the stability of rock layer. By studying the influence rule and influence scope of dynamic pressure of main roadway wall rock because of fully mechanized coal face extracting, that the size of rock pillar was the key of affecting wall rock distorting was proposed. Scientific basis was provided for determining the size of reasonable rock pillar, selecting reasonable extracting support plan and reinforcement measures under different wall rock conditions.

Measurement and numerical analysis of influence of key stratum breakage on mine pressure in top-coal caving face with super great mining height

To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.

Surrounding Rock Failure Mechanism and Control Technology of Gob-Side Entry with Triangle Coal Pillar at Island Longwall Panel in 15 m Extra-Thick Coal Seams

Taking the return air roadway of Tashan 8204 isolated island working face as the background, the evolution law of the stress field in the surrounding rock of the widened coal pillar area roadway during the mining period of the isolated island working face is obtained through numerical simulation. The hazardous area of strong mine pressure under different coal pillar widths is determined. Through simulation, it is known that when the width of the coal pillar is less than 20 m, there is large bearing capacity on the coal side of the roadway entity. The force on the side of the coal pillar is relatively small. When the width of the coal pillar ranges from 25 m to 45 m, the vertical stress on the roadway and surrounding areas is relatively high. Pressure relief measures need to be taken during mining to reduce surrounding rock stress. When the width of the coal pillar is greater than 45 m, the peak stress of the coal pillar is located in the deep part of the surrounding rock, but it still has a certain impact on the roadway. It is necessary to take pressure relief measures to transfer the stress to a deeper depth to ensure the stability of the triangular coal pillar during the safe mining period of the working face. This provides guidance for ensuring the stability of the triangular coal pillar during the safe mining period of the working face.

Rock dynamics in deep mining

Rock mass dynamics disasters caused by excavations and mining occur frequently in deep mines.In order to establish a theoretical system and control technologies for such disasters,we first classify and define dynamic disasters,such as rock bursts,coal bursts,mine pressure bumps,and mine earthquakes.According to the occurrence mechanism of different types of dynamic disasters,we establish a compensation control theory based on excavation and mining effects.On the basis,we propose three key technologies:high prestress compensation technology for the roadway,pressure relief technology using directional roof cutting,and the goaf filling technology using broken rock dilation.These three technologies constitute the compensation control method for dynamic disasters in deep mines.Finally,this method was successfully applied in a deep coal mine with high stress,with monitored results suggesting its rationality.This work provides a new concept and control method for the prevention of rock dynamic disasters in deep mines.

Mechanical model of roof on stope and its analysis

Based on the engineering background of No.8402 stope face in Silaogou Coal Mine of Datong Mineral Bureau and the theory of plate presented by researchers before, considering surrounding rock structure in the stope and according to mechanical property of rock bodies with various kinds of joint planes, presented an assumption that the key roof was divided into a series of elastic plate group by joint planes, then set up mechanical model of elastic plate group with pin joint. After compared the deflection and the stress in the mechanical model by numerical modeling with data from field engineering, the rule of rock plates’ break in turn and the difference in rock plates’ stress during the roof’s first and periodic weighting along the stope face were found.

Floor heave mechanism for gob-side entry retaining with concrete blocks and control method:A case study

The issue of significant floor heave deformation in gob-side entry retaining has long been a challenging problem in the context of longwall mining.This paper studies the floor heave failure mechanism and control method for gob-side entry retaining with concrete blocks in Guizhou Faer Coal Mine in China.Based on Rankine’s earth pressure theory,the effective shear stress equation for the plastic slip of roadway floor is established.The deformation mechanism of floor heave in a retaining roadway with a block wall is revealed in this study.The new comprehensive control method is proposed,encompassing roof pre-splitting blasting for pressure relief,reinforcing cables for roof control,double directions control bolts for concrete block,and pliability cushion yielding pressure.FLAC3D numerical calculation model is established,which shows that the new method can effectively reduce the average vertical stress peak value of the entity coal floor by 34.6%and significantly reduce the pressure source causing the roadway floor heave.Besides,a multi-parameter real-time online monitoring system for mine pressure was designed,and field tests were carried out.The results show that the maximum value of roadway floor heave under the new method is 163 mm,reduced by 66.9%,and the roadway floor heave is effectively controlled.These research findings offer a fresh perspective and new ideas for controlling floor heave in mining operations.