Roadway Model Research Articles

Digital modelling method of coal-mine roadway based on millimeter-wave radar array

The roadway space of coal mine is narrow, and the illumination is low and uneven. Dynamic mining is accompanied by dust and water mist. The accuracy and reliability of roadway data collected by vision and laser sensors are poor. Based on this, a digital modeling method of coal mine roadway based on millimeter-wave radar array is proposed. Firstly, aiming at the problem of complex environmental interference, combined with the characteristics of small amount of single frame data of millimeter-wave point cloud, a multi-layer filtering noise reduction processing and dynamic subgraph registration method of millimeter-wave point cloud is proposed to filter out interference points and realize single radar point cloud registration. Secondly, aiming at the problem that a single millimeter-wave radar cannot scan the complete roadway information at one time, combined with the characteristics of small elevation field of view of millimeter-wave radar, a millimeter-wave radar array acquisition system is built, and an improved iterative closest point (ICP) registration algorithm based on point cloud features is established to construct the roadway point cloud fusion model. Finally, aiming at the problem of uneven and sparse point cloud after array fusion, a Poisson surface reconstruction method based on point cloud density weighted interpolation is proposed to refine the roadway structure and realize the accurate reconstruction of digital roadway model. The experimental results show that the digital modeling method of millimeter-wave radar array can accurately obtain the information of roadway surrounding rock, the density of roadway point cloud is increased by 22.4%, and the average absolute error percentage of the width and height of the reconstructed roadway model is only 0.82% and 0.72%, which provides a new research method for the reconstruction of underground roadway and an important basis for the digital modeling method of coal mine roadway.

Deformation Characteristics and Response Factors of Rock Bolt Body in Roadway with Layered Composite Roof

Layered composite roofs are characterized by developed bedding fissures, resulting in severe deformation and damage of rock bolts at the top of the roadway, as well as a poor roadway support effect. Increasing pretension force is an effective way to enhance the stiffness of the rock bolt support system. To clarify the influence and mechanism of the pretension force on the support effect of rock bolts in the layered roof, a roadway model of the layered roof was established using the interface unit of FLAC3D, and the simulation rock bolts were constructed using the pile unit, which can simulate the mechanical behaviors of rock bolts, such as tension, shear, bending, fracture, and anchor failure, and the pretension force was applied. On this basis, the deformation and failure characteristics and influencing factors of rock bolts in the layered roadway roof under different surrounding rock conditions were simulated and analyzed. The research shows the following: ① Field measurements showed minor shear deformation in the rock bolts at the center of the roadway roof, with lateral displacements of 5.7 cm and 5.3 cm. Significant shear deformation occurred in the rock bolts at the roof corners, with lateral displacements of 18.2 cm and 17.6 cm. ② Simulations of rock bolt deformation characteristics matched the field measurements closely, confirming the reliability of the simulation method, parameter selection, and calculation sequence. ③ The primary factors affecting rock bolt deformation are the structural plane strength and surrounding rock strength. Rock bolts are most susceptible to lateral displacement when the structural plane strength is low, the strength difference between rock layers is large, and the weaker layer is below the structural plane. The presented research can provide a reference for the instability mechanism and support treatment of the layered composite roof roadway.

Feasibility of natural bamboo branches aggregate applied to the thermal insulation layer of rock walls in roadways

The high-temperature heat damage is mainly caused by heat dissipation of surrounding rock in deep mining of mine, so spraying thermal insulation layer (TIL) on mine roadway can be used to actively heat insulation. As a kind of green material, bamboo branches have excellent thermal insulation and mechanical properties. In this paper, gravel and ceramsite were used as aggregate, bamboo branches and glass hollow bead were used as main thermal insulation materials, and the effects of different content, diameter, and length of bamboo branches on mechanical properties, thermal insulation properties, and microstructure were studied through orthogonal experiments. A group of specimens with the best comprehensive performance was selected through the analysis of the efficiency coefficient, and the optimal ratio was determined. This ratio ensures the perfect balance between insulation and strength for TIL, which is essential for the preparation of TIL. At the same time, the numerical simulation software Fluent was used to establish the roadway model, and the cooling effect of the TIL on the airflow temperature in the roadway under different working conditions was studied based on the parameters of the selected specimens. These parameters are based on the actual characteristics of the specimen, and their accuracy ensures the reliability and validity of the research results. The results show that under the optimal mixing ratio, the thermal conductivity (TC) of the specimen is 0.224 W/(m·K), the thermal insulation performance of the prepared coating is increased by 25∼65 %, and the mechanical strength is also improved. The optimal mix ratio obtained in this study can be applied to the field of mine thermal damage control, and the feasibility of natural bamboo branches for preparing roadway thermal insulation material is demonstrated. Bamboo branches grow rapidly, and their use as thermal insulation materials will not only not cause a burden on the environment, but help to promote ecological recycling and achieve sustainable use of resources.

Numerical Simulation of Acoustic Emission Events in Supporting Roadways under Different Dynamic Loads

This paper studies the distribution characteristics of acoustic emission (AE) events in supporting roadways under different dynamic load conditions through numerical simulation and theoretical analysis. According to the principle of AE numerical simulation, the roadway model is established by FLAC3D software, and the supporting structure of the bolt cable is established by editing the Fish function. According to the model dynamic load application criterion, the relationship between the peak velocity of the particle, the distance from the source center to the dynamic impact damage point, and the dynamic load intensity is introduced. The velocity-distance-energy relationship is deduced from the relationship to determine the magnitude of the dynamic load energy. The simulation results show that the intensity of the dynamic load source and the distance of the dynamic load source directly impact the AE events. The larger the dynamic load intensity and the closer to the dynamic load source, the more concentrated the AE events. The roadway has a blocking effect on the transmission of the dynamic load stress waves. According to this characteristic, the roadway can be protected by a high-pressure relief roadway. Rock lithology greatly influences the transmission of dynamic load stress waves and the number of AE events. When the dynamic load stress wave passes through the rock strata of different lithologies, the attenuation of the dynamic load energy and the number of AE events are large. However, when the dynamic load stress wave passes through the rock strata of the same lithology, the attenuation of the dynamic load energy and AE events is small. The surrounding rock structure in the bottom corner area of the roadway is susceptible to disturbance from dynamic load sources above the roadway. The results are greatly significant for studying the AE characteristics of support roadways with disturbance-typeimpact failure.

Effect of a Double-Machine Parallel Air Curtain on Wind Flow in an Underground Roadway of a Coal Mine

In order to study the effect of a double-machine parallel circulation air curtain in intercepting wind flow in a mine roadway, the air curtain jet angle and full fan pressure were analyzed. Taking a metal mine roadway as the engineering background, Fluent numerical simulation technology was used to establish an equi-proportional physical model of the original roadway, and a K45-6 axial flow fan was selected to numerically simulate the flow field inside the original roadway, which was analyzed from three aspects: isolation pressure difference, air leakage volume and wind choke rate. The results show that when the full pressure of the fan is fixed, with an increase in the jet angle of the air curtain, the separation pressure difference and the wind choke rate show a trend of first increasing and then decreasing, and the air leakage volume shows a trend of first decreasing and then increasing. With an increase in the air curtain jet angle, the air curtain convergence gradually forms a complete air curtain, but when the air curtain jet angle continues to increase, the air curtain cannot effectively block the wind flow due to the transverse pressure from the roadway. When the jet angle is too small or the full pressure of the fan is too large, the phenomenon of induced air flow will occur, and the two-machine parallel air curtain will direct the air downstream of the roadway to upstream and no longer intercept the roadway air flow. After comprehensive analysis, the effect of wind control is obvious to set up a double-parallel air curtain in the roadway, and the optimal combination of the roadway air curtain is 30° for the full pressure blade of the fan and 30° for the jet angle.

Study on reasonable loading mode of small-scale roadway model and its application in mining engineering

The small-scale roadway model is often used in the fine simulation of mining engineering. The determination of the structure and load conditions of the model has an important influence on the accuracy of the simulation. In this paper, a large-scale stratum model and a small-scale roadway model are established by using finite element method. The optimal loading mode of the roadway model and its applicability under different roof-sidewall stiffness ratios are studied. The simulation accuracy of the roadway model is quantitatively evaluated by comparing the distribution laws of stress field and strain field with those of the stratum models. Under the same roof-sidewall stiffness ratio, the similarity between the simulation results of the roadway model and the stratum model under displacement load is much higher than that under stress load. Under the same load mode, the stress and strain similarity between the stratum model and roadway model increases with the increase of the roof-sidewall stiffness ratio. Furtherly, the simulation application of the roadway drilling pressure relief is carried out. Compared with the large-scale stratum model with small-size elements, the small-scale roadway model under displacement load also shows obvious stress transfer after drilling pressure relief, while it has faster computational efficiency. Finally, a small-scale roadway model simulation method suitable for surrounding rock disaster occurrence mechanism and control is proposed.

Theoretical analysis of dynamic stress distribution around a circular damaged roadway under transient disturbance

AbstractExcavation damaged zone (EDZ) widely exists in the surrounding rock of underground roadway due to blasting excavation, which can further change the surrounding rock property and deteriorate the stability of the roadway. In the presented research, a damaged roadway model was developed to investigate the dynamic stress concentration factor (DSCF) distribution around the damaged roadway under a transient plane P wave. The influencing factors on DSCF distribution were discussed, including the shear modulus (μe/μd) of the intact surrounding rock to that of the damaged surrounding rock, the thickness of EDZ (Rd/R0), and the wavelength of the incident stress wave. Results indicated that the damaged surrounding rock around the roadway belongs to stress‐relaxed zones, and the existence of EDZ can reduce the overall DSCF of surrounding rock. As the ratio of μe/μd is increasing, both the maximum compressive and tensile stress concentrations in the damaged zones decrease gradually, which is opposite to that in the intact surrounding rock. A larger EDZ can induce a higher DSCF in the damaged surrounding rock and a smaller DSCF in the intact surrounding rock. As the incident stress wave's wavelength is increasing, the peak value of DSCF grows first before declining, finally followed by a constant value. Furthermore, the maximum compressive and tensile stress concentrations are always found near the surrounding rock that is perpendicular to and along the incoming direction of stress waves, respectively. The stress concentration in both intact and damaged surrounding rock near the incoming side of stress waves is higher than that at the transmitted side.

The Deformation, Failure Mechanisms, and Stability Control of the Surrounding Rock of Deep Cross-Measure Roadway: A Case Study

In view of the difficulty in controlling the surrounding rock stability of deep cross-measure roadways, a deep cross-measure roadway of the Wanfu coal mine, a typical high-stress mine, was monitored on site and analyzed under the original support scheme. The findings show that the degrees of deformation and failure of the cross-measure roadway varied under different working conditions and that the roadway deformation and failure were mainly characterized by a high fragmentation degree and a large failure range of the surrounding rock and the frequent failure of support components. Considering that the different parts of the cross-measure roadway are located in different lithostratigraphic units, establishing a numerical model of the cross-measure roadway under different working conditions; analyzing the deformation pattern of the surrounding rock of the roadway, the plastic range, and the morphological change pattern; and clarifying the deformation and failure mechanisms of the cross-measure roadway based on field monitoring results. On this basis, two types of evaluation indicators, that is, the deformations of the surrounding rock and the plastic ranges in the four typical parts (roof, shoulder, floor, and sidewalls) of the roadway, were selected to rate the stability of the roadway under different working conditions. Grouting reinforcement-based targeted control countermeasures are proposed to improve the surrounding rock stability. Subsequently, numerical analysis and field application of these control countermeasures were carried out to solve the problem of controlling the surrounding rock stability of deep cross-measure roadways.

Application research of autoregressive and moving average power spectrum in mine ground‐penetrating radar structure detection data analysis

AbstractThe mine roadway built in the same thick rock stratum will not change the lithologic medium in front of the roadway under the influence of the small structure of the mine, which makes the mine radar face many difficulties in structural interpretation. In the coal measure strata in southwest China, the coal seam roof is the weak aquifer of the Kayitou (T1k) group. The mine structure is the excellent drainage boundary of an aquifer, resulting in the water content of the structural belt being different from that of the surrounding rock. This paper proposes a method to identify hidden structures in mine roadways using the autoregressive and moving average power spectrum energy enveloping medium water content inversion technique. Based on the actual water content of strata in the study area, 48 roadway models are constructed. The finite‐difference time‐domain algorithm was used to obtain the forward data and calculate the volumetric water content of the model. The structure of the roadway model is accurately identified by the water content difference. In the numerical simulation study, the segmentation frequency of high‐frequency and low‐frequency envelope of the autoregressive and moving average spectrum of 100‐MHz radar antenna is determined to be 155 MHz, and the value range of water content calculation regulation parameter k is determined. The high‐ and low‐frequency envelope inversion characteristics of the autoregressive and moving average spectrum of different tunnel media models are summarized and analysed. To solve the calculation problem of energy envelope selection of autoregressive and moving average power spectrum of engineering data, the k‐nearest neighbour machine learning algorithm was used to learn and classify the power spectrum features of different tunnel models. The detection application is analysed through the whole‐rock medium and coal and rock medium roadway in the study area. The results show that the method can effectively identify the location and strike characteristics of the hidden structures in front of the roadway.

Numerical simulation research on bolt supports’ mechanical properties deformation in high-stress roadway

With the rapid development of domestic mining industry, it is necessary to consider the safety of the mine when mining. In order to improve the high stress environment and the frequent failure of bolts caused by the increase of excavation depth, in this experiment, FLAC3D is creatively proposed to establish the calculation model of bolt support roadway, analyze the basic geological environment and surrounding rock structure of the research area, and conduct the numerical simulation of the mechanical characteristics of bolt support deformation (BSD) in the high stress roadway (HSR). The basic geological environment and surrounding rock structure of the study area are analyzed, and FLAC3D is adopted for establishing a calculation model of the bolt-supported roadway, which can be used to simulate the axial and lateral forces of the bolt, and then determine the boundary conditions. It is found that the supporting bolt in the roadway needs to bear not only axial tension, but also transverse shear and bending. Based on the Winkler foundation beam principle, a calculation model of the bolt’s lateral bending force in the soft rock roadway is established, the lateral force characteristics of the bolt support are analyzed, the concept of “anchoring composite bearing body” is proposed, and the force characteristics of the bearing body are calculated. The research results show that in the HSR, the bolt mainly bears the combined forces of tensile and lateral bending; among them, the bolt’s axial force remains basically unchanged at the tail part near the pallet, and the bolt’s axial force at the end part deep into the rock mass decreases rapidly. The bending moment of the bolt is “wave-shaped” distributed along the length of the rod body in the positive direction and negative direction of the axis, and the comprehensive action of the axial tension and transverse bending of the bolt increases when the stress concentration increases. A smaller roadway radius will lead to longer bolts, denser arrangement and higher support strength.

Influence of Base-Angle Bolt Support Parameters and Different Sections on Overall Stability of a Roadway under a Deeply Buried High Stress Environment Based on Numerical Simulation

Strengthening the base-angle of a roadway can have a beneficial impact on its overall stability, but the specific optimal parameter selection range is still unclear. Fast Lagrangian Analysis of Continua 3D (FLAC3D) software is used to carry out the stability analysis of 5 kinds of roadway models with different section shapes under the conditions of no support and different base-angle bolt support angles, and the simulation verification is carried out under the actual working conditions of the Sanshandao Gold Mine. The conclusion is as follows: without support, the self-stability of a tri-centric arch roadway is the best, and that of a rectangular roadway is the worst. When the base-angle bolt dip angle is between 15° and 45°, a better supporting effect can be obtained under the established 5 kinds of roadway sections. In the straight wall circular arch roadway of the Sanshandao Gold Mine, the roadway stability is the best when the angle of the base-angle bolt is 15°. However, changing the length of the base-angle bolt, even if the length of the base-angle bolt is increased to a certain extent, will decrease the overall supporting effect of the supporting structure. This paper can provide a reference for the selection of tunnel bottom corner bolt support parameters.

Research on Location Selection of Personnel Door and Anemometer Based on FLUENT

The structural design of ventilation structures and the arrangement of anemometers in the main ventilation roadway of an underground mine play an important role in the accurate measurement of air speed. It is one of the important tasks of mine ventilation management and intelligent-ventilation-system construction to determine the position of anemometers. In this paper, the CFD numerical simulation method is used to determine the position of the personnel door in the automatic air door by FLUENT software simulating and analyzing the air-speed cloud diagram and air-pressure cloud diagram in the two-dimensional roadway model. Under the same air speed, comparing the air-speed distribution of different cross-sections in the three-dimensional roadway model when the wide door and the personnel door are opened, the anemometer is set at the 25 m cross-section behind the air door, and the air-speed distribution of the cross-section at different air speeds is simulated. The average air-speed line and the specific installation position of the anemometer on the line are obtained by Origin software. The result shows that the position of the personnel door is 400 mm from the middle line of the roadway, and the measurement error of the anemometer is small on the left side of the roadway (0.41, 2.45) and the right side of the roadway (4.59, 2.43) at 25 m behind the air door, which provides a theoretical basis for the measurement of air speed in a coal mine ventilation roadway.

Short-wall paste continuous mining and continuous backfilling for controlling industrial square surface subsidence

To facilitate coal mining under the industrial square in Western China, short-wall paste continuous mining and continuous backfilling (PCMCB) is proposed to release the overlaid resources and handle coal gangue. First, the concept of short-wall PCMCB is presented, and the principle of surface subsidence is analyzed. Second, the mechanical model of the branch roadway and strength of the backfill body are established via mechanical derivations. Third, the proportion of backfill materials is calculated. Finally, field applications are carried out in the Dingjiaqu coal mine. The results show the following: 1) Based on the simply supported beam model of the roof and strength design model of the backfill body, the reasonable width of the branch roadway was determined as 5 m and late strength of the backfill body should exceed 2.62 MPa in the Dingjiaqu coal mine. 2) According to the design strength of the backfill body and backfill material proportion, the reasonable ratio of cement: fly ash: gangue: water was determined as 1:1.82:4.17:1.78. 3) In accordance with the equivalent mining height theory, the critical filling rate of the goaf should be more than 90% to ensure that the deformation is within the first level of building damage. 4) The field application shows that subsidence could be effectively controlled by backfilling, the overall surface subsidence was very small, and the maximum subsidence value (77 mm) was far lower than the deformation extremes of the building protection requirements. This study provides practical guidance for the exploitation of overlaid resources under similar shallow burial conditions, which can help in the disposal of coal gangue with considerable social and economic benefits with popularization and application.

Research on the Creep Model of Deep Coal Roadway and Its Numerical Simulation Reproduction

The long-term stability of coal mine roadway engineering is critical to the safe mining of coal resources and the protection of the surface environment. In this paper, the creep test of coal samples in coal roadway was carried out by multi-stage constant load method, and the test results showed that when the stress level was low, the creep curve had a attenuated stage and a steady-state stage, and the steady-state creep rate tended to increase with the increase in the stress level; When the stress level was higher than the yield stress, the creep rate curve appeared to have an acceleration stage after the steady-state stage. The instability failure mode of the coal sample was mainly shear failure with local tension failure. For this, a New Fractional-order Nonlinear Viscoelastic-plastic Rheological Model (NFNVRM) was established by introducing Abel elements and Nonlinear elements, and the constitutive equation of the model was deduced. The new model can fully reflect the stable decay stage and accelerated rheological stages of coal samples, and the parameter identification curve was consistent with the experimental results, which verifies the correctness and reasonableness of the NFNVRM. Meanwhile, based on the FLAC3D secondary development interface, the constitutive equations of the NFNVRM were written into the software to obtain new Dynamic Link Library (DLL) files. The simulation results were consistent with the experimental results when the DLL file was called. Finally, the NFNVRM.dll was applied to predict the surrounding rock deformation of an S mine. The study's findings offer suggestions for environmental protection.

Establishment of a Coal Mine Roadway Model Based on Point Cloud Feature Matching

A coal mine roadway is a longitudinally limited space with curves and branches, low illumination and high humidity, a large amount of dust, and an unstructured terrain environment. Traditional ICP algorithms have the defects of slow convergence speed and it is easy to fall into local optimums. While the NDT algorithm in the NDT + ICP algorithm has high registration efficiency, poor stability, and low registration accuracy, which are not suitable for point clouds with noise and a large amount of data. By calculating the FPFH value, the detailed description of the point cloud will be greatly increased to increase the robustness and accuracy Therefore, a feature registration method based on the FPFH + ICP algorithm is proposed to reduce the modeling error of excavation roadways and meet the requirements of intelligent excavation. First, outliers caused by dust are treated by the Euclidean clustering point cloud segmentation method, and then the calculation of the normal vector in the FPFH feature descriptor is optimized based on extracting key points from the roadway structure. The surface normal vector of each key point and its neighborhood point is estimated according to the measured point and its neighborhood point. The initial coordinate transformation matrix of a point cloud of an excavated roadway is obtained by the SAC-IA algorithm and transferred to the ICP algorithm. Finally, KD-tree is introduced into the ICP algorithm to accelerate the search speed of corresponding point pairs, and the Gauss–Newton method is used to optimize the solution of the nonlinear objective function of the algorithm to complete accurate registration of point clouds in an excavation roadway.

Mechanical performance of a 3D printed scaled mine roadway model

This study exploits 3D concrete printing technology to build a physical model of a mine roadway, 30 times scaled down of its engineering prototype. The supporting arches were also scaled accordingly and then manufactured by 3D metal printing. By assembling the 3D printed concrete model and metal arches, the engineering scenario was reproduced in laboratory for a monotonic increasing loading. Loading was assisted by multiple measurement techniques, namely: digital image correlation (DIC), acoustic emission (AE), strain gauges . Attention was dedicated to the damage initiation and evolution of the 3D printed components. The results highlighted the advantages of the 3D printed model to understand the collapse mechanism of the layered concrete, which involved the collapse nearby the excavation and the failure of the arches. Moreover, the hypotheses and limitations of this study were discussed with advices for future researches. Finally, engineering data from the simulated site were analyzed, and it found that the 3D printed model predicted the actual deformation characteristics of engineering prototype with reasonable accuracy.

Theoretical study and application of energy extreme value discrimination method of softening zone for bursting hazard.

Considering the current situation that it's difficult to quantify the discrimination of rockburst hazard, an analytical solution for the softening zone energy of surrounding rock under rockburst in a circular roadway is obtained theoretically based on the elastoplastic softening model of a circular roadway. The critical softening zone energy, critical softening zone radius, critical roadway shrinkage displacement, and critical roadway shrinkage rate are determined. An energy extreme value discrimination method of softening zone for bursting hazard is proposed. The critical softening zone energy is taken as the evaluation basis of the bursting liability of the coal seam where the roadway (a full coal roadway) is located. The uniform energy index, which is the ratio of the external disturbance energy of the surrounding rock softening zone to the critical softening zone energy, is used as the evaluation basis for bursting hazards. Theoretical analysis shows that the smaller the critical softening zone energy of the roadway surrounding rock is, the stronger the bursting liability of the coal seam is, and the greater the uniform bursting hazard index is, the stronger the bursting hazard of the roadway. Subsequently, based on the critical softening zone energy and the uniform energy index, a classification standard of bursting liability and an evaluation method of bursting hazard are proposed. The reliability of the softening zone energy extremum criterion, the bursting liability classification standard, and the bursting hazard evaluation method was verified through indoor and field tests. The energy extreme value discrimination method of softening zone for bursting hazard considers the internal and external factors of roadway rockburst comprehensively and can judge the rockburst risk through field real-time observation, which is a more scientific and reasonable method to predict the risk of roadway rockburst. The research work has important theoretical guiding significance for the prevention and control of roadway rockbursts.

Deformation Prediction and Analysis of Soft Rock Roadway with High Altitude and Large Buried Depth Based on Particle Swarm Optimization LSTM Model

Deformation prediction is an important basis for roadway information construction, especially for soft rock roadway at high altitude and large buried depth, whether the deformation of roadway surrounding rock can be effectively and accurately predicted is an important basis for judging the stability of roadway surrounding rock. However, at present, the research on the informatization construction of the roadway is not in-depth, and the intelligent prediction technology for the deformation of the surrounding rock of the roadway is still in its infancy, and the accuracy of deformation prediction is also low. Therefore, based on the research of domestic and foreign researchers, in order to solve the breakthrough of related technology, this paper puts forward the deformation prediction and control technology of high altitude and deep buried soft rock roadway based on a neural network model. This method is based on the traditional prediction model and is replaced by the neural network, so as to improve the problems of low accuracy and large prediction deviation in the related deformation prediction of the traditional prediction model. At the same time, aiming at the problem of poor local weight and network search ability, an improved method using particle swarm optimization algorithm is proposed, which effectively considers the influence of local and global factors on the combined weight. Finally, the improved deformation prediction model of high altitude and deep buried soft rock roadway based on particle swarm optimization LSTM model is applied to an engineering example and compared with the traditional model to explore its feasibility and effectiveness. The results show that the prediction model has higher prediction accuracy than the traditional prediction model, and the relative deviation of the prediction results is controlled within 2%. At the same time, compared with other models (BP neural network model), it has relatively higher accuracy and stability. The research results can provide a new idea for the deformation prediction of soft rock roadway with high altitude and deep burial.

Research on Theory and Technology of Floor Heave Control in Semicoal Rock Roadway: Taking Longhu Coal Mine in Qitaihe Mining Area as an Example

Abstract As one of the most common disasters in deep mine roadway, floor heave has caused serious obstacles to mine transportation and normal production activities. The third section winch roadway in the third mining area of Qitaihe Longhu coal mine has a serious floor heave due to the large buried depths of the roadway and the semicoal rock roadway, and the maximum floor heave is 750 mm. For the problem of floor stability, this paper establishes a mechanical model to analyze the stability of roadway floor heave by analogy with the basement heave of deep foundation pit. It provides a model reference for analyzing the problem of roadway floor heave. Aiming at the problem of roadway floor heave in Longhu coal mine, the roadway model is established by using FLAC3D, and the roadway model after support is established according to the on-site support measures. Through the analysis of the distribution of roadway plastic area, stress nephogram, and displacement field simulation results, the results show that the maximum displacement of roadway roof and floor after support is reduced by 15% and 23%, but the maximum floor heave is still 770 mm, which is close to the measured floor heave of roadway. In order to solve the problem of roadway floor heave and integrate economic factors, this paper puts forward three support optimization schemes, simulates the support effect of each scheme, and finally determines that scheme 3 is the best support optimization scheme. Compared with that under the original support, the amount of floor heave is reduced by 81%, and the final amount of floor heave is 150 mm, which can meet the requirements of roadway floor deformation. The results provide a scheme and guidance for roadway support optimization.

Study on the Optimization and Oxygen-Enrichment Effect of Ventilation Scheme in a Blind Heading of Plateau Mine.

There are abundant mineral resources in plateau areas, but it is difficult to extract them safely because the problem of hypoxia in plateau mines seriously affects the life and health of workers. In order to address the problem of hypoxia in the blind heading of a plateau metal mine, a three-dimensional roadway model was established based on field data of the Pulang copper mine in Yunnan province, China. The computational fluid dynamics (CFD) method was used to explore the optimal type of oxygen supply duct outlet, and to reveal the oxygen diffusion law influencing different ventilation factors. Grey correlation analysis was used to study the correlation values of the ventilation factors on the oxygen-enrichment effect in blind headings, such as forcing duct position, exhausting duct position, and extraction pressure ratio. The results demonstrated that the oxygen-enrichment effect of a slit oxygen outlet was better than that of the traditional oxygen supply method. When the direction of the oxygen outlet hole was 30° and the height above the roadway floor was 1.95 m, the oxygen increase effect was better than other forms of oxygen supply duct outlets. Grey correlation analysis revealed that the major influencing factors of the oxygen-enrichment effect in the roadway of the plateau mine, were, in descending order, as follows: forcing duct position, extraction pressure ratio, and exhausting duct position. This study has a positive guiding significance for improving the respiration environment in blind headings of plateau mines.