In order to solve the problem of tight mining succession in single wing mining mines, there is often a situation of opposite excavation when facing the mining face. During the excavation of the mining face, the law of rock pressure manifestation and the width of the coal pillar are the key to ensuring the safe mining of the tunnel excavation and working face. Taking the 100303 transportation roadway of a certain mine as the engineering background, theoretical analysis, numerical simulation, on-site monitoring and other methods were used to study the reasonable width of coal pillars and the law of rock pressure behavior during the excavation period. The main conclusion is that through theoretical calculation, under the dual influence of excavation disturbance and working face mining, the width that ensures the existence of elastic core and incomplete plastic failure of the coal pillar is at least 30m. Numerical simulations have found that when the heading of the excavation is 20~30m ahead of the meeting position, the deformation of the surrounding rock increases, and the deformation of the coal pillar and mining side both exceeds 0.5m. When the excavation reaches a certain distance behind the goaf, the deformation of the surrounding rock is accelerated due to the combined influence of excavation disturbance and lateral support stress in the goaf, resulting in severe deformation of the coal pillar wall, with a maximum deformation exceeding 1m. When the excavation distance of the 100303 transportation roadway is 70m from the 100302 fully mechanized mining face, the excavation should be stopped, and the support parameters should be optimized within the disturbance range to improve the bearing capacity of the coal pillar. On site monitoring shows that the deformation of the top, bottom, and two sides of the tunnel is relatively small and within a controllable range, effectively controlling the deformation of the surrounding rock of the excavation face in the face of mining.

Abstract: In view of the technical problems of roadway layout in the extra-thick coal seam with residual coal pillars after close-distance coal seam mining, Tangshan coal mine was taken as the research object and the failure depth of the floor after mining in the upper coal seam, the stress distribution of the floor of the residual coal pillar and the reasons for the failure of the roadway roof in the lower coal seam under the uneven load were studied by using the theoretical analysis , numerical simulation and field measurement. The research shows that the maximum failure depth caused by the abutment stress caused by the upper coal seam mining is 31.5 m, which affected the lower coal seam. The vertical stress distribution of the coal pillar floor has obvious non-uniformity distribution and the lower coal seam retrieval roadway is more likely to reach the tensile limit and produce deformation damage. The characteristics of the main stress distribution under four types of roadway arrangement in the lower coal seam were also compared and the internal staggered and translational arrangements were preferred. Furthermore, the unbalanced degree of stress and deformation of the roof of the mining roadway was evaluated by combining the stress change Δσ and displacement change ΔD of the roadway. Combined with the numerical simulation and field industrial test data, the optimal inner stagger distance of the mining roadway in the working face of 9 coal seam is 37.5 m, which provides a reference for the layout of the extra-thick coal seam mining roadway.

Aiming at the problem that a large number of room mining failure areas left by the early mining of shallow coal seams seriously affect the normal mining of the working face at this stage, taking the occurrence and mining conditions of the 15301 working face of No.5-1 coal seam in Wujiagou Coal Mine as the research background, the coal mine exploration robot and the airborne three-dimensional laser scanning system are used to explore the three room mining areas near the 15301 auxiliary transportation roadway. The instability mechanism of the room mining failure area is studied, and the support strength of the failure area is determined. Through the experiment of different proportions of filling materials, the reasonable filling scheme is determined. Combined with the exploration of filling effect, the technology of safe and rapid passage through the filling area is proposed. The research and practice show that when the support strength Pk≥2.1 MPa in the failure zone, the instability of the failure zone can be avoided. It is determined that the main filling material is filling material I with cement and fly ash mixing ratio of 3:7 and water cement ratio of 1:(0.8~1.2), which is the main material to meet the filling of Wujiagou Coal Mine ; after the filling of the room mining area, the safe and fast passing through the filling area technology was used to successfully complete the filling and remining of the room mining failure area of the 15301 working face, and good technical and economic benefits were obtained. It provides technical reference for shallow coal seam mining under similar conditions.

Abstract: In order to solve the problem of wasteful use of steel by reference to experience in the design of round pipe belt conveyor joist structure, an optimal design method based on Design of experiment (DoE) is proposed. The design of the steel joist is based on design of experiment (DoE). The load combinations of the round pipe belt conveyor joist are analysed, and the loads are applied in Ansys workbench according to the most unfavourable load combinations of the joist to identify the dangerous bars. Multi-objectives Genetic Algorithms (MOGA) was used to carry out multi-objective optimization. The results show that the overall mass of the optimised truss structure is reduced by 32.8%, resulting in a lighter structure; at the same time, the stress ratios of the bars are increased but meet the strength and stiffness requirements, and the bar sections are more fully utilised.

In order to finely identify the disasters caused by the previously unknown small coal mine goaf in the Yiyuan Coal Mine of Shenfu Mining Area, and provide scientific basis for goaf management, it is necessary to carry out comprehensive exploration techniques such as transient electromagnetic method, drilling, and logging to investigate the distribution range and water abundance of the goaf.The results show that from the logging curve, it can be seen that the physical properties of the coal layer are stable, and the curve shape is obvious. The coal seam has high resistivity, low density, and low gamma characteristics. The coal seam belongs to a high resistivity layer with poor conductivity (up to 1000Ω·m), while other mudstone, sandy mudstone, sandstone, etc. exhibit relatively low resistivity characteristics. The physical properties of the coal seam and surrounding rock differ significantly;The transient electromagnetic method adopts a parameter combination of 280m rectangular emission wire frame, emission frequency of 25Hz, gain of 22-25, emission current of 8A, and integration time of 15s for detection. The known goaf is clearly reflected, and it is inferred that the total area of the pillar type goaf in the 3-1 coal seam is 0.985km2;Through drilling, the 2-2 coal and 3-1 coal room pillar type goaf were exposed, verifying the geophysical inference of the 3-1 coal goaf. Logging, transient electromagnetic exploration, and drilling are interdependent and complementary, achieving the goal of refined and comprehensive exploration.

Aiming at the problems of large deformation, high degree of fragmentation and difficult support of extremely soft surrounding rock under the action of deep high stress, taking the 1232 ( 3 ) gob-side entry of Dingji Coal Mine as the engineering background, the failure characteristics of surrounding rock and the principle and technology of stage control of surrounding rock in deep high stress soft rock gob-side entry are studied by means of numerical simulation, field monitoring and underground test. The results show that with the increase of the distance from the head of the roadway, the asymmetry of the stress of the two sides of the roadway increases gradually. The peak stress of the solid coal side is 37.18 MPa, which is greater than 35.21 MPa of the coal pillar side. There is stress concentration in the 50 m range of 1242 ( 3 ) final mining line, up to 33 MPa. The development degree of the plastic zone of the surrounding rock of the roadway is that the coal pillar side is greater than the solid coal side, which is greater than the roof and floor. From the complex surrounding rock change process experienced in the process of roadway excavation, the whole roadway is divided into five typical stages of surrounding rock change to analyze the deformation and failure characteristics and failure mechanism of surrounding rock. It is revealed that under the action of high stress, the deformation of surrounding rock in deep soft rock roadway along goaf is large, showing obvious regional and asymmetry in space. Based on the preliminary design scheme of the roadway and the deformation and failure characteristics of the surrounding rock, the support scheme is adjusted in a timely and effective manner, and the roadway is comprehensively treated in a segmented, asymmetric and regional manner, forming a long-term mechanism for the control of the surrounding rock of the deep soft rock roadway, which provides theoretical and technical support for the ground pressure control of the same type of deep soft rock roadway.

Baijigou Coal Mine adopts stratified mining，and the transport roadway of 0102303 working face is situated beneath the goaf． The roof of the construction channel is a metal mesh false roof，and the original support is seriously deformed due to the disturbance of the upper stratified goaf． For this purpose，the jacking trapezoidal concrete-filled steel tube support is designed，and the jacking performance of various types of supports was tested through grouting jacking test． The test results showed that the grouting effect of Φ194mm×10mm steel pipe was good，and the jacking force reached 3.93kN，which met the requirements of the jacking of the support and the initial support of the tunnel false roof． In order to increase the bending strength of the steel pipe beam，the bending round steel is set in the hollow steel pipe，and the calculated support reaction force is 2.3MPa，which is 5.4 times higher than the original support method． At the same time，in order to solve the installation difficulties of various kinds of supports in the roadway，a lifting bracket installation machine has been designed，and the lifting force can reach 6.8kN． After 30 days of grouting，the basic area of the support load is stable, and the maximum value of the support load within half a year of installation is 0.8MPa． The on-site monitoring shows that the top and bottom moving in and the convergence of the two sides are less than 50mm，and the supporting effect is good．

Aiming at the difficult problem of controlling the peripheral rock of the bottom plate roadway under the disturbance of the working face mining, taking the group of cross-mining bottom plate roadway of 1315 working face of Anju Coal Mine as the research background, we analyzed the distribution characteristics of the roadway peripheral rock of the overburden working face during the process of mining back by numerical simulation and on-site practice, and analyzed the distribution characteristics of the roadway peripheral rock of the overburden working face and the plasticity zone. The research results indicate that when the working face advances to a stop line of 100m, the influence range of the over-supporting pressure is about 35.8m in the horizontal direction and 37.8m in the vertical direction, and the subgrade roadway is affected by the mining according to the size of the distance to the working face successively, which is of process nature. Aiming at the characteristics of 3 upper coal bottom roadway group peripheral rock subject to disturbance and deformation, the proposed "anchor mesh cable + T-type steel belt + metal mesh" joint support technology program, on-site monitoring shows that the support program effectively control the deformation of peripheral rock in the bottom roadway group, to ensure the stable use of the roadway group underneath the face during the period of mining back.

In order to study the influence of short-distance coal seam mining on the damage and oxidation characteristics of coal pillars in the upper working face, taking the 74201 working face in Bailu Coal Mine as the research background, based on numerical simulation and experimental research, the influence of short-distance coal seam mining on the plastic regional distribution and oxidation characteristics of coal pillars in the upper working face was analyzed. FLAD3D simulation results show that with the advance of 4-2 coal seam, the failure and deformation characteristics of coal pillars in the upper coal seam are approximately divided into three stages: the coal pillars are complete; The coal pillar is deformed and damaged, but it maintains basic continuity; The coal pillar is sheared and broken in a large range. The temperature programmed experiment shows that the critical temperature points of CO and C2H4 are advanced by 10~20℃ in the secondary oxidation process of coal pillars that have been oxidized to a certain extent, and the oxygen consumption rate increases by 2573.1×10-11 mol/(cm-3 s) at the highest. C2H2 was not detected in the intact coal pillar, C2H2 gas was detected in the 4-1 fractured coal pillar and 4-1 fractured coal pillar at 250℃ and 240℃ respectively, which proved that it entered the stage of violent oxidation. It was concluded that the coal pillar crushing process promoted the secondary oxidation process of coal to some extent, and the fractured coal pillar was more prone to spontaneous combustion than the intact coal pillar. This study draws the conclusion that the spontaneous combustion risk of broken and unstable coal pillars in upper coal seam increases with the mining in lower coal seam.

The activation of large faults leads to frequent occurrence of coal bump disasters in coal mine. Ensuring sufficient distance between the mining face and the fault is one of the key measures to control such coal bump disasters. Taking the large thrust fault in Yima mining area as an example, this paper analyzes the spatial shape and movement characteristics of the fault and their correlation with coal bump based on geological borehole detection and settlement observation. Based on the induction of coal bump behavior and similarity simulation of fault slip, a reverse proportional relationship between the number of coal bump and distance of face-fault is proposed, and the safe distance between the working face and the fault to avoid fault slip is obtained. Working face supersedure between two mines under thrust fault conditions is carried out, and the coal bump prevention effect is evaluated with microseismic monitoring. The results show that the fault plays a dominant role in the horizontal stress environment of the shallow part, and the surface uplift of the hanging wall of the fault is higher than that of the footwall during the process of fault slip which induces the coal bump behavior in the working face. The closer the working face is to the fault, the more obvious the fault movement is, the higher the frequency and energy of coal bump behavior, and the minimum safe distance between the working face and the fault to avoid fault activation is 455m. Compared with the coal face mining near the fault, it significantly reduces the fault activation frequency, coal bump degree and microseismic energy during mining of far-fault face in the area of Yuejin and Changcun coal mine. The results provide a theoretical basis for the control technology of coal bump under the condition of large faults.

With the gradual complexity of coal mining conditions, the difficulty of gas management in outburst coal seam is gradually increasing, and the extraction method with fixed hole spacing is difficult to meet the demand of efficient and collaborative management in gas occurrence areas. Taking 2091 working face of Linhua Coal Mine as the engineering background, a differentiated extraction technology based on visualization of gas geology is proposed to replace the previous extensive design mode of extraction borehole. Specifically, the information related to gas geology is input into the gas geology visualization system to realize the dynamic display and visualization of gas geology information on the working face through the system; Define the gas content criteria, identify and divide the low gas area, medium gas area and high gas area in the working face area, and design differentiated extraction boreholes according to the mining schedule under the principle of "should be pumped to the full"; Through the anti-outburst information analysis module, the prediction chart is automatically generated to effectively identify the blank zone of gas control and further optimize the design of extraction borehole. The research shows that the overall extraction time of 2091 working face is controlled within 30~150d, the residual gas content is in the range of 4.53~5.88m3/t, the concentration of return air gas is in the range of 0.22~0.41%, and the concentration of gas in the upper corner is in the range of 0.30~0.47%, so as to realize the efficient and collaborative treatment of gas disaster in 2091 working face.

This article proposes a short-circuit protection method based on detecting multi-point current signals at different locations. The illumination protection circuit in a coal mine is divided into multiple blocks, and the magnitude and phase of the phase voltage and current will change when different faults occur in different blocks. Based on this, the fault type and the specific location of the short circuit point in a certain block can be determined, and corresponding protection measures can be taken. Compared with the short-circuit detection method of traditional illumination signal comprehensive protection devices, this protection method greatly improves the accuracy and is not affected by the power supply distance. It can locate the short-circuit fault, determine the block where the fault occurs, and classify the fault. Meanwhile, a simulation model of the illumination power supply system is built according to the actual situation in the mine to verify the feasibility of the above method.

In view of the problem that the slurry outlet of the secondary mixer is often blocked in the engineering application of continuous mining and continuous gangue cemented filling system in Changcheng No. 6 Mine, the Fluent Euler multiphase flow model and Realizable k-ε turbulent model was used to simulate the transient flow of solid-liquid two-phase flow in mixer based on the sliding grid method. The reasons for blockage were analyzed, and optimization indicators were determined. On this basis, the effects of rotational speed, blade inclination angle, impeller diameter, and impeller number on the stirring effect were studied separately. It was found that increasing rotational speed, increasing blade inclination angle within 45 °, and appropriately increasing impeller diameter and number of impellers can help improve the mixing effect and alleviate blockage. Finally, the improvement plan for the secondary mixer was determined as a rotational speed of 75 r/min, blade inclination angle of 34 °, impeller diameter of 1.3 m, and a 5-layer impeller, which effectively reducing the two-phase flow density at the bottom of the tank and improved the fluidity of the mortar at the outlet.

In order to solve the problems of the deformation and the instability of the tower body caused by the surface movement and deformation above the coal thickness change area, which affect the normal and safe operation of the television signal tower and reduce the coal resource recovery rate. We studied the dynamic protection and foundation reinforcement technology for the radio and television signal tower above 13031 coalface of Baiping Coal Company. Based on the calculation and analysis of ground movement and tower deformation and on-site monitoring, we applied the precision grouting reinforcement technology and the dynamic leveling protection technology for the television tower protection. In order to improve the strength of the foundation and compensate the subsidence of the foundation, we drilled holes in the television foundation for penetration grouting reinforcement. We transformed the fixed tower foundation into a height adjustable foundation. When the tilt of the tower foundation is close to 5mm/m, the height of the four towers can be controlled through the tower height adjustment system in time to reduce the tilt deformation of the tower. These results suggest that the tilt of the tower has security risk and the inclination of the base is greater than 4mm/m twice while the 13031 working face is in the range of -200m~+180m from the center of the TV signal tower. On the basis of grouting reinforcement, the tower was levelled twice with dynamic levelling device. The tower tilt deformation value was less than the upper limit during the mining surface deformation activity period. the radio and TV signal tower was in good operation condition.

In order to explore the difference between the overburden migration and surface damage in the shallow extremely thin coal seam by roof cutting and pressure relief mining without coal pillar and the conventional coal pillar retaining mining, based on the key stratum theory and the shallow extremely thin coal seam in Zichang mining area, the formula for calculating the critical value of the hard rock breaking distance and the overburden caving height is obtained. Combined with 3DEC numerical simulation and field tests, The characteristics of overburden migration and surface damage in shallow extremely thin coal seams under the conditions of non pillar mining and coal pillar retaining mining are compared and analyzed, and the heights of the two overburden zones in extremely thin coal seams are determined. The results show that when the mining face reaches 60m, the development height of the two belts is basically stable. When the mining face is larger than 60m, the cracks in the overburden behind the working face gradually close from cracks, and the crack area moves forward with the mining face, and the height of the two belts is stable at 24.6~27.7m; Compared with the conventional coal pillar retaining mining, the overburden under the roof cutting and entry retaining mining without coal pillar is continuously moving and deformed, which can effectively repair the overburden cracks and surface damage cracks caused by the discontinuous movement and deformation on both sides of the coal seam mining face, and eliminate the overburden cracks on both sides of the coal pillar in the adjacent working face section under the conventional coal pillar retaining mining method, which is well verified by field observation.

In order to solve the problem of difficult control of surrounding rock in broken roadway of coal seam in short distance, the control effect of surrounding rock before and after grouting with hollow grouting cable was studied based on theoretical analysis and numerical simulation, that is to say, the mechanism of the surrounding shear stress between the hollow grouting anchor cable and the surrounding rock before and after grouting. The results show that the pre-grouting anchorage section conforms to the viscoelastic constitutive model, and the shear stress curve increases linearly to a nonlinear decrease and then to a stable single peak, after grouting, the pre-stress field around the roadway forms a gradual whole along the anchor cable, which redistributes the stress field around the roadway and reduces the shear stress strength, the stress curve changes from quadratic linear to nonlinear and then to stable double peak curve, which can effectively improve the shear strength of broken surrounding rock and soft rock roadway.

Accurate prediction of coal seam gas content is an important link to prevent underground gas disasters. In order to improve the scientificity and accuracy of underground gas content prediction, 41 sets of data from different mining areas are obtained, including gas content, buried depth, coal thickness, moisture, ash and volatile content. Five algorithms of least square support vector machine (LSSVM), deep belief network (DBN), Long short-term memory (LSTM), Elman neural network and adaptive enhancement (Adaboost) are selected, and the optimal base model is the least square support vector machine (LSSVM), adaptive enhancement and deep belief network. Seven gas content prediction models are integrated through the base model, and four models of Stacking- LSSSVM-Adaboost, Adaboost, Stacking-Adaboost-DBN and Stacking- LSSSVm-Adaboost-DBN are optimal models. Four prediction and evaluation indexes, namely, decision coefficient, mean absolute error, root mean square error and mean absolute percentage error, were used to comprehensively evaluate the four selected models, and the models with MAE < 0.2, RMSE < 0.3 and MAPE < 10 were selected as the final prediction models for gas content. The results show that the decision coefficient of the integrated Stacking-LSSVM-Adaboost-DBN model is 0.951, and MAE, RMSE and MAPE are 0.170, 0.204 and 7.412, respectively. The established model has high prediction accuracy and can provide a basis for mine gas disaster prevention.

In order to solve the problem that gas emission from coal mining face can not be predicted accurately in real time, the difficulties and treatment methods of gas content inversion in working face are expounded by analyzing the sources and influencing factors of gas emission from mining face. On this basis, the inversion model of gas content is established, and the dynamic prediction method of gas emission from working face based on gas content inversion is put forward. The prediction method is based on the premise that the occurrence state of gas in coal is a continuous change, and the amount of gas emission is predicted through the inversion of coal gas content in working face and the determination of gas emission characteristic coefficient. The industrial test in a coal mine in Shaanxi shows that the prediction method can better predict the amount of gas emission from the coal face. The absolute error range between the predicted value and the measured value of gas emission is between 0.09~0.20m3/min, and the error percentage is controlled within 20%. The application of this prediction method can make real-time and continuous prediction of gas emission from mining face, ensure the safe and efficient production of coal mine, and provide technical support for the prevention of coal and gas outburst and gas overrun.

Abstract: The hydration of gas and water is used to promote the solidification of gas gas in the coal seam in the form of hydrate, which can prevent the rapid desorption of coal seam gas in the process of mining and eliminate the danger of coal and gas outburst. Therefore, this paper independently designed the experimental device for pressure-resistant hydration reaction, carried out gas hydration experiments, and investigated the effects of accelerator concentration and initial pressure on the formation of gas hydrates. The results showed that the addition of accelerator effectively increased the hydration effect but there was a limit concentration, when the accelerator concentration was between 0.1~0.3 mol/L, it would promote the hydration process, and the best effect was when the concentration reached 0.3 mol/L, and when the accelerator concentration was 0.5 mol/L, it would slow down the hydration process. The initial pressure was positively correlated with the hydration effect, and the higher the initial pressure, the faster the rate of hydration and the longer the hydration time. The monitoring of the methane component in the reaction residual gas shows that the accelerator and initial pressure can change the process of hydration, which plays a decisive role in the solidification effect of gas hydration.

In order to solve the problem of subjective analysis and single index in the fire risk assessment of mining belt, this paper proposes a comprehensive evaluation method of fire risk of mining belt based on entropy weight method and grey correlation degree method. By using NBS smoke density test box and cone calorimeter, the key influencing factors of fire risk such as light transmittance, heat release rate, smoke generation rate and CO generation rate of mine belt fire smoke were analyzed, and a multi-level evaluation index system of mine belt fire risk was established. The fire risk of mine belt under different thermal radiation conditions was comprehensively evaluated. The results show that under the thermal radiation intensity of 50 kW/m2, the light transmittance of mine belt decreases rapidly, and decreases to 0 at 70 s. Compared with the heat radiation intensity of 25 kW/m2, the peak heat release rate and total heat release at 35 kW/m2 increased by 29.06% and 36.22%, respectively, the peak smoke production rate and total smoke production increased by 45.55% and 31.54%, respectively, and the time to reach the peak smoke production rate was shortened by 92.59%. The weight ranking of fire risk factors of mine belt is : combustion risk ( 0.5216 ) > smoke risk ( 0.2522 ) > toxic gas risk ( 0.2261 ). The research results can provide basic support for the formulation of mine belt fire escape route.

In order to effectively identify the unsafe behavior of underground coal miners, we designed an underground personnel behavior intelligent detection system based on lightweight OpenPose algorithm. The lightweight OpenPose network was used to obtain the coordinates of key points of human skeleton from infrared camera data, and then different recognition algorithms were designed to detect fall, climb and push postures. Experimental results showed that, the algorithm achieved a speed of 30 f/ s and the overall accuracy was 86. 35%. After deploying the detection model to industrial computers and integrating it with alarms, accurate real-time detection and timely alarm notifications for unsafe behaviors was achieved.

To study the influence of underground mining on the deformation and failure of the overlying open-pit mine dump, the Suancigou coal mine and the Harwusu open-pit mine dump were taken as the research objects, and the regulations of surface subsidence and its induced dumps were analyzed. The mechanism of deformation and failure was predicted by the probability integral method, and the deformation and surface subsidence of the dump were analyzed with the FLAC3D software. At the same time, the displacement changes of the Harwusu open-pit mine dump after the stoping of Suancigou coal mine working surface were analyzed. The results shown that the maximum subsidence predicted by the probability integral method was about 21 m, and the maximum subsidence calculated by FLAC3D simulation was about 22 m. The maximum surface subsidence of both increased first and then gradually stabilized with the progress of the mining phase. The surface subsidence forms the regulation of moving basins. The numerical simulation results were consistent with the actual location of the subsidence area. The horizontal displacement of the dumping was positively correlated with the advance length of the working face. In the direction of the working face, the horizontal displacement on both sides of the goaf was the largest, showing the characteristics of sliding to the middle of the goaf, and the overall performance was that the horizontal displacement of the left slope is greater than that of the right slope.

It is of great significance to understand the gas migration rule in the caving zone in order to improve the extraction efficiency of coalbed methane (CBM). In this study, self-designed gas permeability test equipment for crushed coal and rock mass was developed. By virtue of this equipment, we carried out compaction-permeability tests on crushed anthracite of 0.32-0.63 mm particle size. The results show that:(1) The dynamic gas flow process in crushed anthracite can be divided into two representative types (type I and type II) before the stable sorption equilibrium is achieved..(2) There is a quasi-threshold pressure gradient of gas migration in the crushed anthracite at low Reynolds number. And the quasi-threshold pressure gradient decreases with the growth of porosity.(3)The permeability of crushed anthracite is logarithmically positively correlated with the gas pressure; the permeability decreases exponentially with the decrease of void ratio. (4)With the increase of axial stress, the crushed anthracite is transformed from elastic deformation to inelastic deformation, and the sensitivity of permeability to axial stress decreases at this time.

The use of hydrocarbon oil collectors is an important means to optimize the slurry preparation effect of coal flotation and achieve efficient separation where there are few studies focused on the impact of collector kinetic energy. In this study, an improved flotation machine and a single kerosene droplet-slime particle collision test system were used to analyze the change of collector kinetic energy under different energy input factors and its impact on the collector-slime adsorption rate. With the increase of mixing time and energy input, the adsorption firstly increases to the maximum then gradually decreases as it is a physical process. When it progressively reaches the saturation state, the dynamic balance of adsorption and desorption is broken with the continuous input of energy. Which will pull the adsorbed kerosene desorb again, resulting in the decrease in adsorption rate, the maximum adsorption rate is 79.82%, under the 40 s mixing time. The change of impeller speed also changes the kinetic energy of the collectors. As the dispersion of particles and reagents increases, the collision probability increases and the adsorption rate increases. When the impeller speed increases from 500 r/min to 700 r/min, the adsorption rate of the collector slime will increase from 78.11% to 79.82%. This research results explore the influence of collector kinetic energy on the adsorption rate from the perspective of multiple variable factors. Which can provide theoretical reference for the influence of collector kinetic energy on the mechanism of slime slurry mixing.

Abstract: In order to strengthen the stratification of mixed particles on the screen surface and improve the screening effect of traditional vibrating screens. Based on the void-filling effect of mixed particles under vibration and based on the Lissajous vibration synthesis theory, a composite vibrating screen is proposed. The theoretical basis and working principle of the composite vibrating screen are explained and verified using the discrete element method. A comparative study of conventional vibrating screen and composite vibrating screen discrete element simulation was carried out with composite, linear, elliptical and circular vibrating screens with frequency, amplitude and vibration direction angle as variables, and the comparison results showed that the composite vibrating screen has more significant advantages in both screening efficiency and material handling. A composite vibrating screen can give the particle an excitation force along the width of the screen surface, the particle in xyz three directions has the effect of excitation force; the particle force is more diversified, the mixed particle system is looser, more active, better stratification effect, and thus the composite vibrating screen can achieve ideal screening effect.

Hydrogen and oxygen isotopes are widely used as tracers in hydrology, hydrogeology, ecology, soil science, biogeochemistry and other research fields. Coal mining has a certain disturbance to the surface ecology. In the process of ecological restoration and treatment in coal mining area, the problem of ecological water level is an unavoidable scientific problem. In this study, Shendong mining area is selected as the research area. In order to explore this scientific problem, a certain abundance of hydrogen and oxygen isotopic water is artificially put in as a tracer to carry out in-situ tracer research. According to the hydrogen and oxygen isotopic values of plant water extracted and tested from the stems and leaves of surface plants, the limit depth of plant water absorption and reasonable ecological water level are analyzed. The results show that, firstly, the soil moisture content changes little from the surface to 2.5m, and gradually increases and peak at about 2.5m-3.5m, and then decreases and tends to be stable to the deep; Secondly, by analyzing the isotopic characteristics of plant stems and leaves, the limit depth of water absorption of Artemisia annua is 2.5-3M; In addition, the mixsiar model was used to analyze the water content of which soil section was mainly used by Artemisia annua. The soil section at the depth of 240cm was divided into 12 layers, of which the water contribution rate of 60-80cm, 80-100cm and 100-120cm was relatively low, and the contribution rate of other layers was nearly 9%. This study provides a scientific basis for ecological restoration and treatment in Shendong mining area.

Coal is the main energy in China, and its dominant position will not change fundamentally in the next 30 years, but with the reform of the coal supply side structure, coal enterprises face the pressure of reducing production capacity. Because of the complexity of coal industry production conditions and the complexity of coal management structure, coal enterprises have an urgent need for data management and business decision-making. Therefore, this paper combines the information foundation of the current large coal energy enterprises in the development of big data, discusses the application of big data in enterprise intelligent decision-making, according to the actual production and operation data of BT coal department of National Energy, creates the production constraint model, monthly coal supply and coal purchase calculation model and decision-making model. The model is deployed to the server and applied to coal mine WL and coal mine LJH. The results show that the model performs well. The validity of the model is verified by empirical analysis of the actual data of coal mine.

In this paper, starting from the water inlet mode, taking the self-balancing multistage centrifugal pump as the research object, the influence of the water inlet balancing device on the performance of the suction chamber of the self-balancing multistage centrifugal pump is explored. The distance between the center of the balance water pipe and the outlet of the water entry balancing device and the diameter of the balance water pipe were taken as design variables. 5 groups of different comparison schemes were constructed based on the equally spaced control variable method. The external characteristics, pressure distribution, velocity streamline distribution and cavitation performance of the 5 groups of schemes were simulated and analyzed by CFD method. The results show that the head and efficiency of the self-balancing multistage centrifugal pump can be affected by the presence, location and size of the balance water pipe. In the test scheme, the range of centrifugal pump head is 2 m and the range of efficiency is 0.27 percentage points. As the distance between the center of the balanced water pipe and the outlet of the water inlet balancing device or the diameter of the balanced water pipe becomes smaller, the high pressure area in the suction chamber increases obviously, while the eddy current density decreases obviously, and the flow line becomes smoother. The cavitation area in the suction chamber decreased significantly, and the maximum volume fraction of the suction chamber of the optimized scheme was 90.91%, which was 5.4% lower than the maximum volume fraction before optimization. This study can effectively improve the performance self-balancing multistage centrifugal pump suction chamber, and provide a basis and reference for optimization and design of multistage centrifugal pump.

For the special working conditions such as harsh environment and complex geology in the downhole automatic control process of the anchor drilling arm, it is necessary to consider the parameter selection of PID, and for this reason, the stochastic fractal search algorithm (SFS) is used for the adjustment of the PID parameters. Due to the problems of insufficient local search capability and easy to fall into local optimization, the random fractal search algorithm is ineffective in the face of many parameters to be calibrated and serious coupling between parameters of the robotic arm. Therefore, chaotic initialization, positive cosine strategy, and adaptive K value selection strategy are introduced to improve the local search ability and global search speed of the algorithm; Cauchy and differential directional variation strategies are adopted to make the algorithm jump out of the local optimum. The standard test function test shows that the improved stochastic fractal search algorithm has improved the convergence speed and accuracy. Finally, through the simulation experiment of anchor drilling arm parameter adjustment, it is shown that: the overall adaptability value of the PID parameters adjusted by the improved stochastic fractal search algorithm is increased by 21%; and the quantitative indexes of the joints indicate that the improved stochastic fractal search algorithm jumps out of the local optimum, and improves the overall searching accuracy and speed.optimal and improves the overall optimization accuracy and speed.