Mine Laneway Research Articles

Research on Predicting the Safety Factor of Plain Shotcrete Support in Laneways Based on BO-CatBoost Model.

In general, the design of a safe and rational laneway support scheme signifies a crucial prerequisite for ensuring the security and efficiency of mining exploitation in mines. Nevertheless, the conventional empirical support system for mining laneways faces challenges in assessing the rationality of support methods, which can compromise the safety and reliability of the laneways. To address this issue, the safety factor was incorporated into research on laneway support, and a safety evaluation method for laneway support in line with the safety factor was established. In light of the data from a specific iron mine laneway in central China, the CRITIC method was employed to preprocess the sample data. Going one step further, a Bayesian algorithm was utilized to optimize the hyperparameters of the CatBoost model, followed by proposing a prediction model based on the BO-CatBoost model for evaluating laneway safety factors of plain shotcrete support. Furthermore, the performance indexes, such as the root mean square error (RMSE), the mean absolute error (MAE), the correlation coefficient (R2), the variance accounts for (VAF), and the a-20 index, were determined to examine the predictive performance of each proposed model. In contrast to the other models, the BO-CatBoost model demonstrated the optimal predictive output item for safety factors with the lowest RMSE and MAE, the largest R2 and VAF, and an appropriate a-20 index value of 0.5688, 0.4074, 0.9553, 95.25%, and 0.9167 in the test set, respectively. Therefore, the BO-CatBoost model was proven to be the most appropriate machine learning method that can more accurately predict the safety factor, which will provide a novel approach for optimizing laneway support design and laneway safety evaluation.

A Multimodal Robust Simultaneous Localization and Mapping Approach Driven by Geodesic Coordinates for Coal Mine Mobile Robots

Mobile robots in complex underground coal mine environments are still unable to achieve accurate pose estimation and the real-time reconstruction of scenes with absolute geographic information. Integrated terrestrial-underground localization and mapping technologies have still not been effectively developed. This paper proposes a multimodal robust SLAM method based on wireless beacon-assisted geographic information transmission and lidar-IMU-UWB elastic fusion mechanism (LIU-SLAM). In order to obtain the pose estimation and scene models consistent with the geographic information, the construction of two kinds of absolute geographic information constraints based on UWB beacons is proposed. An elastic multimodal fusion state estimation mechanism is designed based on incremental factor graph optimization. A tightly coupled lidar-inertial odometry is firstly designed to construct the lidar-inertial local transformation constraints, which are further integrated with the absolute geographic constraints by UWB anchors through a loosely coupled approach. Extensive field tests based on coal mine robots have been conducted in scenarios such as underground garages and underground coal mine laneways. The results show that the proposed geodesic-coordinate driven multimode robust SLAM method can obtain absolute localization accuracy within 25 cm with practical robustness and real-time performance in different underground application scenarios. The wireless beacon-assisted geodesic-coordinate transmission strategy can provide a plug-and-play customized solution for precise positioning and scene modeling in complex scenarios of various coal mine robot application.

Mine Personnel Positioning System Based on Dual-Wavelength Phase Unwrapping

During the construction of coal mine laneway, due to the particularity of the geographical location and structure of the laneway, its accidents often occur, causing great trouble to the personal and property safety of the construction personnel. Therefore, according to the environmental characteristics of the coal mine tunnel and the positive correlation between the phase envelope range and the wavelength, this paper proposes a structural design of the personnel positioning system of the coal mine tunnel based on the dual wavelength phase unwrapping, which combines the coherent detection structure with the dual wavelength phase measurement method in digital holography. In order to reduce false positives in the position information, the synthetic wavelength is used to increase the spread range of the phase. The experiment shows that this structure can reduce the false positioning without reducing the positioning accuracy, and the average double wavelength phase demodulation can reduce the positioning false alarm by 82.5%, which greatly improves the accuracy of the prediction of the tunnel construction safety, brings great protection to the personal and property safety of the tunnel construction personnel, and improves the mining efficiency of the coal mine.

Effect of Different Bend Pipes on the Propagation Characteristics of Premixed Methane-Air Explosion in Confined Spaces

To explore the effect of different bend pipes on the propagation characteristics of premixed methane-air explosion, the experimental explosion pipe system and numerical model were established. By adopting the comparative analysis of experiments and numerical modeling, it conducted researches on the overpressure evolution of gas explosion shock wave in pipes with different bends and obtained the expressions of attenuation coefficient of shock wave overpressure. The results showed that the change of pipe direction accelerated the attenuation of gas explosion shock wave. The propagation attenuation of gas explosion in the bend pipe was mainly affected by the bending angle and initial peak overpressure before bending. With the increase of the bending angle, the attenuation coefficient of gas explosion shock wave gradually increased. For the same bending angle, the attenuation coefficient of gas explosion shock wave increased with the increase of gas volume. The obtained coupling relationships between attenuation coefficient, bending angle, and initial peak overpressure before bending were useful for estimating the overpressure value after the bend. The results presented in this paper have important significance for the assessment of structures that have been damaged in the mine laneway of gas exploration accidents, further enriching the gas exploration spread theory.

Computational Fluid Dynamic Simulation of Inhaled Radon Dilution by Auxiliary Ventilation in a Stone-Coal Mine Laneway and Dosage Assessment of Miners

Inhaled radon status in the laneways of some Chinese stone-coal mines is a cause of concern. In this study, computational fluid dynamics simulations were employed to investigate three flowrates of the dilution gas (2.5, 5, and 7.5 m3/s) and radon distributions at realistic breathing levels (1.6, 1.75, and 1.9 m). The results showed that there are obvious jet-flow, backflow, and vortex zones near the heading face, and a circulation flow at the rear of the laneway. A high radon concentration area was found to be caused by the mining machinery. As the ventilation rate increased, the radon concentrations dropped significantly. An airflow of 7.5 m3/s showed the best dilution performance: The maximum radon concentration decreased to 541.62 Bq/m3, which is within the safe range recommended by the International Commission on Radiological Protection. Annual effective doses for the three air flowrates were 8.61, 5.50, and 4.12 mSv.

A Case Study of an Optimized Intermittent Ventilation Strategy Based on CFD Modeling and the Concept of FCT

With the increasing operation costs and implementation of carbon tax in the underground coal mining systems, a cost-effective ventilation system with well methane removal efficiency becomes highly required. Since the intermittent ventilation provides a novel approach in energy saving, there still exists some scientific issues. This paper adopts the design concept of frequency conversion technology (FCT) to the ventilation pattern design for the first time, and an optimized intermittent ventilation strategy is proposed. Specifically, a real excavation laneway of a coal mine in China is established as the physical model, and computational fluid dynamic (CFD) approaches are utilized to investigate the spatiotemporal characteristics of airflow behavior and methane distribution. Plus, the period of intermittency and appropriate air velocity are scientifically defined based on the conception of FCT by conducting the parametric studies. Therefore, an optimized case is brought out with well methane removal efficiency and remarkable energy reduction of 39.2% in a ventilation period. Furthermore, the simulation result is verified to be reliable by comparing with field measurements. The result demonstrates that a balance of significant energy saving and the methane removal requirement based on the concept of FTC is possible, which could in turn provide good operational support for FTC.

Research on Gas Exploration Shock Wave Spread Law via One-Way Bifurcation Pipeline

In order to research on gas exploration shock wave spread law via a one-way bifurcation pipeline, the gas exploration pipeline experimental system and numerical calculation model were established. By adopting the comparative analysis of experiments and numerical modeling, it conducted researches on the attenuation and shunt characteristics of the gas exploration shock wave via the one-way bifurcation pipeline and obtained the computational formulas for shock wave attenuation coefficients of branch pipelines and straight pipelines and shock wave shunt coefficients of branch pipelines. As the research result showed that when the pipeline bifurcation angle was fixed, the larger the shock wave overpressure was, the larger the overpressure attenuation coefficients of straight pipelines and branch pipelines were. When the shockwave overpressure was fixed and the one-way bifurcation pipeline angle increased, the shock wave overpressure attenuation coefficients of branch pipelines would be aggregated and the shock wave overpressure attenuation coefficients of straight pipelines would be decreased, which reflected the shunting action of the shock wave in branch pipelines and straight pipelines; the larger the branch pipeline bifurcation angle, the smaller the shunting action for straight pipelines. The research achievements in the paper had important significance for the assessment of structures damage in mine laneways gas exploration accidents and installation of the antiexploration manhole cover, which further enriched gas exploration spread theory.

A Time Varying Ventilation and Dust Control Strategy Based on the Temporospatial Characteristics of Dust Dispersion

Generally, an effective ventilation system is essential to reduce coal dust disaster. However, with the implementation of carbon tax and increase of energy and operating costs, it is urgent to design a cost-effective ventilation and dust control system. In this paper, a real driving face in an excavation laneway of coal mine in China was taken as the physical model, and the temporospatial characteristics of airflow and dust dispersion is investigated for the first time to design an original conception of time-varying ventilation and dust control strategy. Specifically, computational fluid dynamic (CFD) approaches are utilized to investigate the dynamic regularity of airflow behavior and dust dispersion, and parametric studies are conducted to select the appropriate ventilation pattern, which is validated to be potential in energy saving as well as dust removal efficiency. In addition, based on the selection of key time point according to the regularity of dust concentration changed over time, the most effective type of speed function is brought out for this novel ventilation system, which reduces energy usage up to 15.11% in a ventilation period. Furthermore, the accuracy of simulation result is verified by field measurements, which demonstrates that adjusting the ventilation velocity at the appropriate time point (case 7) can effectively control the dust concentration, which performs as well as the steady flow. The research results suggest that the further understanding of temporospatial characteristics of dust dispersion is helpful for ventilation design, and significant energy savings and dust removal requirements are verified to be possible in the proposed scheme.

Numerical study on dust movement and dust distribution for hybrid ventilation system in a laneway of coal mine

Coal dust disaster is the most serious problem in a laneway of coal mine. Dust movement regularity for comprehensive mechanized heading face is the key scientific issues for the principle and technology of dust prevention. The special topic on systematic study of the variation regularity of dust movement and dust distribution is presented with hybrid ventilation for the comprehensive mechanized heading face: Euler–Euler method was firstly established on the numerical platform for gas–solid two phase flow in a laneway. And the forces and the dynamic model of dust particles were performed in three-dimensional flow field. Then based on the visible simulations, the movement characteristics of diffusion, sedimentation and accumulation of dust particles were investigated under the action of the complex air flow, and the spatiotemporal variation of dust distribution was studied with hybrid ventilation system. Meanwhile, the obtained dust distribution regularities were compared with the obtainable experimental results. Finally, selected method on different ventilation patterns for dust control was brought out for the heading face according to the gained regularity. The research results is helpful for further understanding of the essence of dust movement with air flow, which could provide more suitable guidance for the principle of dust control and technology of ventilation.

Principle of Well-Net Design for Coalbed Methane Exploitation in Coal Mine Area

There are abundant CBM (Coalbed Methane) in China. These CBM has caused a remarkable problem to the coal-mining in China. In order to improve the structure of Chinese energy and eliminate the risk of coal mine gas, the relevant industries and sections have implemented many explorations in CBM enriched areas. With great achievements, there are many important problems in the actions of CBM exploitation. The disadvantageous interaction of the surface CBM well and the later coal mining has been ignored at all. There are many disadvantages and defects. To solve these problems and eliminate or weaken the disadvantageous, the scientific and reasonable design of surface CBM well location is an important step. With the thinking of surface condition, coal mining plan, the arrangement of coal mine laneway, the direction and scale of the in-situ stress, and thinking more about the negative influence to and of surface CBM well, according to the theories of mining dynamics, mining engineering, mining geomechanics, and the CBM engineering, the design theory of the surface CBM well net can be studied. Finally, the arrangement principle of CBM product well in coal field is presented. The existing or future coal pillar will be a critical location for the surface CBM well location.

Mine Laneway Modeling and Realization Based on the Matlab

In view of the request of 3D visualization on mine laneway, according to traverse measurement data and profile data, by use of triangulated irregular network, the shortest dagonal method and the adjacent feature points to pace method ,using Matlab language, the 3D laneway body were established. The result shows that the method is feasible and has a simple and fast reconstruction method.

Radio Channel Research in Coal Mine Laneways

The transmission mode of wireless waves in coal mine tunnel is different from the mode in free space.The multipath propagation of wireless wave is severe in tunnel.As a result,the characteristics study of multipath propagation is very important to the design of wireless communication system in coal mine tunnel.After analyzing the multipath propagation attenuation in tunnel,the statistics of single frequency signal,narrowband signal and broadband signal are obtained.This is the foundation for the application of resisting multipath decline techniques.

Strategies for Sensor Node Deployment Based on Spatial Correlation for Methane Sensor Network

It is infeasible to deploy dense sensor nodes with power supply for methane sensor network in laneway, because the laneway is narrow, and its environment with excessive dirt, dust, moisture is harsh. So, it is urgent for WSN in coal mine laneway to lower the energy cost. First, a hierarchy methane sensor networks topology and deployment is described in this paper. Then, a spatial correlation model for saving significant energy in methane sensor networks is given, and a computational method of distortion measure for MMC is derived. Using the computational method, the strategies for deploying sensor nodes for saving significant energy are (1) Selecting the appropriate number of contributed nodes, the optimal trade-off between power constraints and distortion measure can be achieved. (2) Locating contributed sensor nodes, minimum methane estimation distortion can be achieved.

Research on the characteristics of noise source on heading face and noise propagation in mine laneway

Based on the complexity and dynamic random analysis of machine noise source in mine heading face, this article established the noise pressure mathematical model of noise propagation in mine laneway of different noise sources, carried out noise propagation numerical simulation in long space, and revealed noise propagation law of more radiated noise sources in the mine roadway. The results show that, under conditions that the total noise power is always the same, regardless of point source, surface noise source, or body noise source, the corresponding noise attenuation trend along the mine laneway and attenuation curve shape are basically the same. However, the attenuation velocity corresponding to complex stereo noise source is slower than single point source and the noise pressure value is higher than the single point source. The actual noise of measured values is close to the theoretical value or, say, there is little error for complex stereo noise source, whereas the error to single point source and surface noise is higher, respectively.

Fine analysis on advanced detection of transient electromagnetic method

Fault fracture zones and water-bearing bodies in front of the driving head are the main disasters in mine laneways, thus it is important to perform their advanced detection and prediction in advance in order to provide reliable technical support for the excavation. Based on the electromagnetic induction theory, we analyzed the characteristics of primary and secondary fields with a positive and negative wave form of current, proposed the fine processing of the advanced detection with variation rate of apparent resistivity and introduced in detail the computational formulae and procedures. The result of physical simulation experiments illustrate that the tectonic interface of modules can be judged by first-order rate of apparent resistivity with a boundary error of 5%, and the position of water body determined by the fine analysis method agrees well with the result of borehole drilling. This shows that in terms of distinguishing structure and aqueous anomalies, the first-order rate of apparent resistivity is more sensitive than the second-order rate of apparent resistivity. However, some remaining problems are suggested for future solutions.

Remote Wireless Monitoring System for Heading Face of Coal Mine Based on WMN

t is necessary to establish a remote wireless monitoring system for the heading face of coal mine because of the risk of gas outburst and water inrush. This paper introduced a remote wireless monitoring system for heading face of coal mine based on wireless mesh network. The key technology is that the wireless backhaul link of this wireless communication system must remain high bandwidth and low latency after multi-hop in order to support video transmission because the laneway of coal mine is narrow and long. We used the technology of multi-interface multi-channel to design a 2-interface 3-channel backbone network for this wireless communication system. Each node of this backbone network is equipped with two interfaces, and three orthogonal channels of channel 1,6,11 provided by 802.11b/g are used. Compared to single interface single channel chain network, the 2-interface 3-channel wireless mesh backbone network has high throughput and low end to end delay while using appropriate channel allocation algorithm to make the channels of adjacent links non-interfered.

Mine laneway 3D reconstruction based on photogrammetry

Aiming at the problem of 3D reconstruction for mine laneway, the technique route and step were given based on digital close range photogrammetry and traverse surveying. 3D coordinates of laneway traverse point, photogrammetric station, control strip points were obtained by electronic total station based on mine coordinate system. The feature points were extracted from the scene images. The camera was calibrated by direct linear transformation (DLT). 3D relative coordinates of the arbitrary feature points in mine laneway were calculated after feature points being matched, in which the origin of coordinate system is photogrammetric station. The 3D absolute coordinates of the feature points in mine laneway can be obtained by the combined adjustment of photogrammetry and non-photogrammetric observations and coordinate conversion. The measurable 3D model of the underground laneway terrain surface was constructed with the 3D coordinates of feature points on the image pairs obtained. The measurable 3D model of a corridor was reconstructed by the mentioned method and the experiment precision with an average standard deviation of 0.013 6 m between the 3D model and practical measure was obtained by electronic total station. The experimental resulted show the validity of the proposed approach.

Application of Comprehensive Reinforce Technology in Soft and Crumbly Surrounding Rock in High Stress

Based on soft and crumbly surrounding rock of roadway, poor integrity of roof, drench water in roadway, the large in-situ stress and other complex conditions, this paper analyzes the cause of roadway destruction and grouting strengthening mechanism, using the coupling of grouting technique to integrated strengthening for the region. Engineering application shows that the integrated strengthening effect is obvious, and the economic and technique effectiveness is remarkable. The successful application of secondary coupling grouting technology provides the reference for the mine laneway construction of similar geological conditions.

Dynamic numerical simulation of coal mine fire for escape capsule installation

Fire in mine laneway leads to disordered ventilation system airflow, and smoke will result in staff poisoning. In such situation, it necessitates to install a rescue capsule in the common staff area. In this paper, the software Fluent was used to simulate the airflow conditions dynamically in No. 5 belt roadway of Kongzhuang Coal Mine when fire broke out. The migration law of CO front was determined. By underground escape experiments, personnel escape velocity model in pathway was established. Based on the numerical simulation and results of field experiments, the escape capsule installation location in the passageway of No. 5 belt roadway was ascertained.

High resolution numerical simulation of methane explosion in bend ducts

In this paper we developed a parallel code, adopting a fifth-order weighted essentially non-oscillatory (WENO) scheme with a third-order TVD Runge-Kutta time stepping method for the two-dimensional reactive Euler equations, to investigate the propagation process of methane explosion in bend ducts. In the simulations, an inverse Lax–Wendroff procedure is adopted to construct a high order boundary in order to treat the complex boundaries. The numerical results show that when the bend angle is 30° and 45°, it cannot inhibit the propagation of the detonation wave; while when the angle reaches 60° and 75°, the detonation wave finally attenuates to the shock wave. It indicates that the propagation of the detonation wave can be inhibited. Furthermore, the temperature and the pressure at the entrance of the bend are low. When the angle arrives at 90°, the detonation wave evolves into cellular detonation when it passes through the bend. When the angle is larger than 90°, the detonation wave dramatically attenuates at the diffracting point, and later some hot spots can be formed, which can ignite the combustible gas nearby. Thus the second explosion occurs and finally the detonation is formed. When the angle is larger than or equal to 90°, the temperature and the pressure at the entrance of the bend is too high that the rescue efforts in the methane explosion accidents will encounter great difficulties. Hence, the laneway with 60° and 75° bend can inhibit the propagation of the detonation wave, and the temperature and the pressure at the entrance of the bend is not too high as well. All the results above can provide an important basis for the design and optimization of the mine laneway.