Support design of main retracement passage in fully mechanised coal mining face based on numerical simulation

For the comprehensive mechanised coal mining technology, the support design of the main withdrawal passage in the working face is an important link to achieve high yield and efficiency. Due to the impact of mining, the roof movement of the withdrawal passage is obvious, the displacement of the coal body will increase significantly, and it is easy to cause roof caving and serious lamination problems, and even lead to collapse accidents, which will affect the normal production of the mine. In this paper, the mining pressure development law of the main withdrawal passage support under the influence of dynamic pressure is designed, the most favourable roof failure form of the withdrawal passage is determined, and the action mechanism and applicable conditions of different mining pressure control measures are studied. The pressure appearance and stress distribution in the final mining stage of fully mechanised coal face are studied by numerical simulation. The deformation and failure characteristics and control measures of roof overburden in the last mining stage of fully mechanised coal face are analysed theoretically. Due to the fact that periodic pressure should be avoided as far as possible after the full-mechanised mining face is connected with the retracement passage, some auxiliary measures such as mining height control and forced roof blasting are put forward on this basis. The relative parameters of the main supporting forms are calculated. The main retracement of a fully mechanised working face in a coal mine channel is put forward to spread the surrounding rock grouting reinforcement, reinforcing roof, and help support and improve the bolt anchoring force, the main design retracement retracement channels in the channel near the return air along the trough for supporting reinforcing surrounding rock control optimisation measures, such as through the numerical simulation analysis, the optimisation measures for coal mine fully mechanised working face of surrounding rock is feasible. Numerical simulation results also show that the surrounding rock control of fully mechanised working face of coal mine design improvements, its main retreat channel under the roof subsidence, cribbing shrank significantly lower, and closer, to better control the deformation of surrounding rock, achieved significant effect, to ensure the safety of coal mine main retracement channel of fully mechanised working face support.

Research on Mechanisms and Control Measures of Surrounding Rock Disaster in Large Section Roadway with Top Coal under the Influence of Tectonic Stress

Based on the research background of large section roadway with top coal (LSRTC) in thick coal seam mining in Wangzhuang Coal Mine, Shanxi Province, China, catastrophe characteristics of the surrounding rock of the LSRTC were investigated and summarized. Based on the principle of damage mechanics, the critical size discriminant of the LSRTC was deduced, and the induction mechanism of section size effect and tectonic stress effect on the roadway surrounding rock disaster was revealed. Accordingly, the roadway surrounding rock control principle with the basic idea of “stabilizing and controlling top coal, reconstructing the coal wall, and limiting floor heave” was put forward, and the roadway surrounding rock stability control countermeasures with the core technology of “strong pressure support for roof + grouting reinforcement for two sides + bolt barrier for floor angle” were developed, which solved the surrounding rock control problem of the LSRTC under the action of tectonic stress and provided a useful reference for the difficult problem of roadway surrounding rock control under similar conditions.

Surrounding Rock Control Technology When the Longwall Face Crosses Abandoned Roadways: A Case Study

When a working face is crossing the abandoned roadways, problems such as roof subsidence, rock fracture, and instability will occur, resulting in widespread roof fall and rib spalling, which seriously affect safe and efficient mining on the working face. In this paper, the no. 23 coal pillar working face of Juji coal mine is taken as the engineering background, a mechanical model of crossing the abandoned roadways is constructed aimed at the problem of the working face crossing the abandoned roadway group, the collapse of the abandoned roadway roof is analyzed, a scheme of crossing the abandoned roadways is designed, and the development law of the stress and plastic zone after the reinforcement scheme is stimulated and analyzed. The results show that when the working face advances to the abandoned roadway, key block B crosses the abandoned roadway and the solid coal to form a “cross-roadway long key block.” It is calculated that the minimum support resistance required for the abandoned roadway is 6700 kN. Based on the results of numerical comparison, it is concluded that filling wood pile when the working face passes through the roof abandoned roadway and adding anchor cables for reinforcement support when the working face crosses the coal seam abandoned roadway effectively reduce the stress concentration of surrounding rocks, decrease the development of the plastic zone, and achieve safe and efficient mining when the working face crosses the abandoned roadways.

Research on Hydraulic Fracturing Pressure Relief Technology in the Deep High-Stress Roadway for Surrounding Rock Control

With the increase of mining depth in underground engineering, deep ground pressure has an extremely unfavorable impact on safety production and the economic benefits of coal mines and the control of the roadway stability in deep mines are gradually highlighted. In this study, the working face 14203 of the Zaoquan coal mine was taken as the engineering background, the deformation mechanism of surrounding rock in the deep-buried high-stress roadway was analyzed, and the hydraulic fracturing pressure relief technology in the advanced roadway was proposed for surrounding rock control. Finally, the numerical simulation and field tests were used to validate the comprehensive effect of the proposed technology. Without damaging the roadway stability in the working face, the hydraulic fracturing pressure relief technology can optimize the stress environment and stability of the roadway through the artificial control of the roof fracture position. The numerical simulation shows that under the action of hydraulic fracturing, the cutting slot is formed, the deformation and failure mode of the roof are changed, the stress of surrounding rock is reduced, and the development of the plastic zone of surrounding rock is limited. As a result, the stability of surrounding rock in the roadway is effectively protected. The field test shows that after the adoption of hydraulic fracturing pressure relief technology, the roof subsidence, floor separation, bolt stress, and cable stress decrease, and the deformation of surrounding rock is reduced significantly. Therefore, hydraulic fracturing pressure relief technology is verified as an effective method to control the large deformation of the surrounding rock in the deep-buried roadway.

Study on the Stability Principle of Mechanical Structure of Roadway with Composite Roof

With the typical composite roof roadway and roof fall accidents in the Guizhou Province of China as the research background, the expression of damage parameters of composite roof was deduced according to Weibull statistical distribution, generalized Hooke’s law and Mises yield criterion, and the influence of shape and scale parameters of Weibull on damage characteristic was discussed. Based on the infinite slab theory, the expressions of deflection and layer separation of each layer of the composite roof were obtained, the critical load expression of each delamination was determined, and the influence of roadway width, overlying strata load, elastic modulus, shape parameters and scale parameters on the stability of composite roof was explored. The research shows that the bolt support can effectively reduce the layer separation between the composite roofs and enhance the stability of the composite roof. On this basis, it is proposed that for the surrounding rock control problem of roadways with composite roof, the active support technology with bolts as the core should be adopted.

Research on the Reasonable Coal Pillar Width and Surrounding Rock Supporting Optimization of Gob-Side Entry under Inclined Seam Condition

In order to study the optimal coal pillar width and surrounding rock control mechanism of gob-side entry under inclined seam condition, the 130205 return air entry adjacent to 130203 gob in Yangchangwan No. 1 well is taken as a typical engineering background. By means of engineering background analysis, theoretical analysis based on inside and outside stress field, numerical simulation by FLAC3D software, and in situ industrial test and relevant monitoring methods, the optimal coal pillar width and surrounding rock control technology are obtained. The results show that the influence range of inside stress field is about 12.2∼12.8 m based on theoretical calculation result; under the influence of 10 m coal column, the overall deformation of the roadway is relatively small and within the reasonable range of engineering construction, so the width of the coal pillar along the return air roadway is set to 10 m which is more reasonable; the cross-section characteristics of special-shaped roadway lead to asymmetric stress distribution and fragmentation of surrounding rock, and then the asymmetric surrounding rock control technology under the coupling effect of roof prestressed anchor + high-strength single anchor cable + truss anchor cable support is proposed. The monitoring results of this support method are effective for the maintenance of gob-side entry, and the study conclusions provide new guidance for the surrounding rock control mechanism of gob-side entry under inclined seam conditions.