Determining the rational layout parameters of the lateral high drainage roadway serving for two adjacent working faces

To determine the rational layout parameters of the lateral high drainage roadway(LHDR) serving for two adjacent working faces, a mechanical model of the LHDR under mining influence was established, and the overburden fissure, mining-induced stress distribution rules were analyzed. First, the development characteristics of mining-induced overburden fissure and the stress distribution law of the upper section of the working face were analyzed. Second, by analyzing the distribution law of vertical stress at different layers, the lateral distance of the LHDR was determined as 25 m. Third, by analyzing the surrounding rock deformation effect, stress distribution law, and overburden fissure distribution law of the LHDR at the heights of 20, 25, and 30 m away from the roof, the rational horizon of the LHDR was determined to be 25 m. Finally, an example of a LHDR located 25 m above the roof of the No. 2 coal seam and 25 m away from the No. 2-603 working face was presented. Results show that when the No. 2-603 coalface is being mined, the surrounding rocks lag 80 m or even further and the working face tends to be stable. The relative deformations of the roof and floor of the roadway and both of its walls were 583 and 450 mm,respectively. The reduction rate of the roadway section was 21.52%–25.32%. The section of the roadway was sufficient to extract the pressure relief gas in the overburden of the No. 2-605 working face. The average gas concentration and the pure volume at the branch pipeline were 24.8% and 22.3 m^3/min,respectively, showing that the position of high-level boreholes was reasonable.

Study of energy-efficient heat resistance and cooling technology for high temperature working face with multiple heat sources in deep mine

In the present research,we proposed a scheme to address the issues of severe heat damage,high energy consumption,low cooling system efficiency,and wastage of cold capacity in mines.To elucidate the seasonal variations of environmental temperature through field measurements,we selected a high-temperature working face in a deep mine as our engineering background.To enhance the heat damage control cability of the working face and minimize unnecessary cooling capac-ity loss,we introduced the multi-dimensional heat hazard prevention and control method called"Heat source barrier and cooling equipment".First,we utilize shotcrete and liquid nitrogen injection to eliminate the heat source and implemented pressure equalization ventilation to disrupt the heat transfer path,thereby creating a heat barrier.Second,we establish divi-sional prediction models for airflow temperature based on the variation patterns obtained through numerical simulation.Third,we devise the location and dynamic control strategy for the cooling equipment based on the prediction models.The results of field application show that the heat resistance and cooling linkage method comply with the safety requirement throughout the entire mining cycle while effectively reducing energy consumption.The ambient temperature is maintained below 30℃,resulting in the energy saving of 10%during the high-temperature period and over 50%during the low-temperature period.These findings serve as a valuable reference for managing heat damage in high-temperature working faces.

Theoretical and numerical analysis of coal dust separated by centrifugal force for working and heading faces

In order to meet engineering needs of Chinese underground coal mines,a new dust-collecting fan,a device of dust separated by centrifugal force in driven cyclone passageway(DCCP)was designed.In centrifugal dust removal section(CDRS)of DCCP,a general equation is derived from the principle of force equilibrium.According to CDRS structure parameters and fan running parameters,the general equation is simplified,and the simplest equation is calculated numerically by MATLAB.The calculation results illustrate that increasing quantity of air current is against dust removal,but it is beneficial to dust removal by increasing the radius of driven spiral blade and increasing the particle diameter of coal dust.The conclusions show that the dust-collecting structure parameters coupled with the fan running parameters is a novel optimization approach to dust-collection fan for working and heading faces,which is especially suitable for Chinese underground mines.

Spatial-temporal variation features and law of gas concentration in the fully mechanized working face under the condition of intermittent ventilation

Based on the fluid mechanics and mass transfer theory,a mathematical model of the spatial-temporal variation of gas was derived to avoid the gas accident caused by the main fan stopping ventilation under the condition of intermittent ventilation in the tunnel.According to the actual parameters of the tunnel,a numerical calculation model was established.The spatial-temporal variation of gas concentration in the fully mechanized working face under the condition of intermittent ventilation was calculated by using the commercial package Fluent,and the correctness of the calculated results was verified by the actual monitoring data of the mine.Firstly,the gas concentration was calculated under different wind velocities at driving face in coal tunnel,and the result showed that the gas can be carried effectively by the wind when the wind velocity is about 1.8 m/s.Secondly,the distributions of wind velocity and gas concentration at driving face were studied at 1.8 m/s,and the result showed the gas concentration increased gradually with the distance close to the outlet,but the gas concentration almost kept constant at the height of driving face.Thirdly,the distribution of gas concentration was investigated with time after the ventilation was stopped and restarted,respectively.The gas concentration of test point gradually increased with the increment of downtime,when the downtime was 40 min,the gas concentration of test point 3 reached the maximum value.The gas concentration increased gradually and reached the maximum after10 min of restart,then sharply decreased and kept constant.

Putting Faces to Names： Snapshots of Two Committee Meetings, 95 Years Apart, Emphasize Continuous International Cooperation in the Atmospheric Sciences

1.Introduction Spectacular advances have been made in the atmospheric sciences on a global level during a period of one hundred years or more,which is arguably most evident through"the quiet revolution of numerical weather prediction"(Bauer et

The main projects and development status of noise forecasting and controlling on working face in coal mine

Noise from the machine on coal working face seriously influenced the miners' physical and mental health, and also, due to the noise, there may be a major hidden danger in safety from accidents as all safety warning signals may be masked by the noise. This paper summarized the features of mine environmental noise on working face, such as the variety of noise sources, the continuity of high intensity and slow attenuation in narrow space, etc.The main projects about noise forecasting and controlling on working face was emphatically expounded;the development status about mines machinery noise mechanism and environmental noise acoustic characteristics of space-time of these main research topics were also introduced.

Back-and-forth mining for hard and thick coal seams—research about the mining technology for fully mechanized caving working face of Datong Mine

The article introduced the key technology, mining process, and back-and-forth mining method for the caving working face of hard-thick coal seams in Datong mine, and researched this innovations process, optimized the systemic design and working face out-play, tried to perfect the caving mining technology of hard-thick coal seams further.

Mechanism of rock burst caused by fracture of key strata during irregular working face mining and its prevention methods

To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory.Furthermore,the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate theory.Through micro-seismic monitoring,theoretical analysis,numerical simulation and working resistance of support of field measurement,this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working face.The results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure,with the main roof being as an undersurface.The fracture form changes from vertical‘‘O-X"type to transverse‘‘O-X"type with the increase of trapezoidal height.From the narrow mining face to the wide mining face,the suspended width of key strata is greater than its limit breaking width,and a strong dynamic load is produced by the fracture of key strata.The numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate 7447.Also there is a high static load caused by fault tectonic.The dynamic and static combined load induce rock burst.Accordingly,a cooperative control technology was proposed,which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system.

Parametric Analysis of the End Face Engagement Worm Gear

A novel specific type of worm drive, so-called end face engagement worm gear（EFEWD）, is originally presented to minimize or overcome the gear backlash. Different factors, including the three different types, contact curves, tooth profile, lubrication angle and the induced normal curvature are taken into account to investigate the meshing characteristics and create the profile of a novel specific type of worm drive through mathematical models and theoretical analysis. The tooth of the worm wheel is very specific with the sine-shaped tooth which is located at the alveolus of the worm and the tooth profile of a worm is generated by the meshing movement of the worm wheel with the sine-shaped tooth, but just the end face of the worm（with three different typical meshing types） is adapted to meshing, and therefore an extraordinary manufacturing methods is used to generate the profile of the end face engagement worm. The research results indicates that the bearing contacts of the generated conjugate hourglass worm gear set are in line contacts, with certain advantages of no-backlash, high precision and high operating efficiency over other gears and gear systems besides the end face engagement worm gear drive may improve bearing contact, reduce the level of transmission errors and lessen the sensitivity to errors of alignment. Also, the end face engagement worm can be easily made with superior meshing and lubrication performance compared with the conventional techniques. In particular, the meshing and lubrication performance of the end face engagement worm gear by using the end face to meshing can be increased over 10% and 7%, respectively. This investigate is expect to provide a new insight on the design of the future no-backlash worm drive for industry.

A forecasting and forewarning model for methane hazard in working face of coal mine based on LS-SVM

To improve the precision and reliability in predicting methane hazard in working face of coal mine, we have proposed a forecasting and forewarning model for methane hazard based on the least square support vector (LS-SVM) multi-classifier and regression machine. For the forecasting model, the methane concentration can be considered as a nonlinear time series and the time series analysis method is adopted to predict the change in methane concentration using LS-SVM regression. For the forewarning model, which is based on the forecasting results, by the multi-classification method of LS-SVM, the methane hazard was identified to four grades: normal, attention, warning and danger. According to the forewarning results, corresponding measures are taken. The model was used to forecast and forewarn the K9 working face. The results obtained by LS-SVM regression show that the forecast- ing have a high precision and forewarning results based on a LS-SVM multi-classifier are credible. Therefore, it is an effective model building method for continuous prediction of methane concentration and hazard forewarning in working face.

Suitable retention and recovery technology of floor coal at ends of fully mechanized face with great mining heights

在大采矿高度的脸的网关主要沿着煤缝接的房顶被驾驶。为网关高度限制， 13 m 地板煤被保留，离开在脸结束的三角形的地板煤，引起煤的损失。为了改进煤恢复率并且在煤采矿保证设备的效率，面对，我们在脸结束调查了合适的保留方法和地板煤的恢复技术。上面的地板煤能被 shearer 直接与地板 dinting 恢复。在推进了地板 dinting 以后，更低的地板煤被 shearer 与地板 dinting 恢复并且为在一道拖拽网关保护煤方面保留步。地实践证明这个方法能改进恢复与大采矿高度在充分使机械化的工作的脸评估的煤。

Research and Application of Airflow Recirculation System in Working Faces with Leaking Airflow

In order to develop the technology of the controlled recircuIation of airflow in the world, some formulas about the airflow recirculation system in the working face with leaking airflow are deduced,which reduces the error between calculating and real values. on the base of the application of the formulas mentioned above, the problem about lack of airflow in the working face 2712 was solved successfully in Xiandewang Coal Mine.

STUDY ON THE STABILITY OF IMMEDIATE ROOF BLOCKS AT THE END FACE

Using vector-analysis, three kinds of roof blocks at the end face of fully mechanized long wall faces have been studied. Tbe result indicates that with face advancing, the three kinds of blocks may all become key blocks. It is put forward that the key blocks can reach into the scope of angle of fracture through supporting, and the fomulas for calculating supporting force needed for the three key blocks to maintain stadility have been derived.

Analysis and control of hydraulic support stability in fully-mechanized longwall face to the dip with great mining height

The working condition of the hydraulic support in working face can be divided into three kinds of situations in the following: roof fall and collapse with cavity,advancing support and supporting.Took single support with four-pole in longwall face to the dip as research object,control method was studied to avoid support instability in three situations mentioned above.Based on these researches,the major factors of influencing on support stability and its controlling measures were put forward.According to specific conditions of working face 1215(3),which is fully-mechanized and Iongwall face to the dip with great mining height in Zhangji Coal Mine,Huainan Mining Group,the effective measures was taken to control supports stability.

Migration law of respirable dust on a super-long fully mechanized double-shearer working face

In order to understand the migration law of respirable dust and gain reasonable design parameters for dust control on a super-long double-shearer fully mechanized working face, this paper describes research carried out using a numerical simulation package(Fluent) based on gas-solid coupling dispersed multiphase flow model and field measurement to research different technology modes, dust distribution law at different intervals where shearers work in opposite directions on the lower 9303 face, No. 2 Jining Mine,Yankuang Coal Mining Co. Results show that the concentration of dust 3–6 m away from the shearers working in the same directions was large, while the impact area of respirable dust near the shearer increased significantly to 5–6 m with the distance between two shearers working in opposite directions.The concentration of dust on a double-shearer face was considerably higher than that of a face with one shear under the combined effect of wind speed on the face and disturbed wind around the shearer, while the dust concentration near the shearer on the return side was considerably higher than that on the inlet side. The concentration of dust on a double-shearer face along the airflow declined slowly so that dust was hard to control. Simulation results confirmed the results of field measurement, which could provide reference for dust prevention design.

Characteristics of water inflow and chemical grouting treatment of a Liu Yuanzi Coal Mine shaft in the Ordos Basin

During shaft constructing, a borehole water inflow of 30 m3/h was encountered in Liu Yuanzi Coal Mine in the southwestern Ordos Basin, whose aquifer is mainly cretaceous. On the basis of regional hydrogeological conditions, a mercury intrusion method and scanning electron microscope were used in this study. We conclude that the loose, porous and easily collapsible clay particles of the cretaceous aquifer rock mass were the major geological cause for water hazards during the construction of the shaft. We propose an approach of chemical grouting from the working surface and in the end succeeded in blocking the water.