Harsh Underground Environment Research Articles

Study on the corrosion performance of supersonic atmospheric plasma sprayed Cr3C2-NiCr coatings

Purpose Due to the harsh underground environment in coal mining, the surface of hydraulic support columns corrodes severely, resulting in significant economic losses. Therefore, a highly corrosion-resistant coatings is needed to extend the service life of the columns. Design/methodology/approach This study aims to compare the corrosion resistance of ST-Cr3C2-NiCr (sealed treatment Cr3C2-NiCr) coatings with industrially applied chromium plating. The corrosion failure mechanism of the coatings was investigated. Findings The results demonstrated that the ST-Cr3C2-NiCr coatings exhibited excellent corrosion resistance. After sealing treatment, the corrosion potential of Cr3C2-NiCr coatings was −0.215 V, and the corrosion current density of Cr3C2-NiCr coatings was lower than that of the plated parts. Practical implications ST-Cr3C2-NiCr coatings prepared by supersonic atmospheric plasma spraying could provide excellent corrosion resistance in the coal industry. Originality/value The low porosity and the presence of the NiCr phase were crucial factors contributing to the preferable corrosion resistance exhibited by the ST-Cr3C2-NiCr coatings. The corrosive process of the coatings involved layer-by-layer delamination of surface oxide film, sub-surface pitting, formation and degradation of sub-surface passive film, as well as severe block-like delamination.

Mining security assessment in an underground environment using a novel face recognition method with improved multiscale neural network

Overstaffing production in underground coal mining is not convenient for daily management, and incomplete information of coal miners hinders the rescue process of firefighters during mine accidents. To address this safety sustainability issue, a novel face recognition method based on an improved multiscale neural network is proposed in this paper. A new depthwise separable (DS)-inception block is designed and a joint supervised loss function based on center loss theory is developed to construct a new multiscale model. The miniers can be recognized in the harsh underground environment during the life rescue. Experimental results show that the accuracy, recall and F1-score indexes of the proposed method for the miner face recognition in the underground mining environment are 97.26%, 94.17% and 95.42%, respectively. Transfer model with joint supervised loss can effectively improve the recognition accuracy by about 0.5–1.5%. In addition, the average recognition accuracy of the proposed face recognition method achieves to 91.34% and the miss detection rate is less than 5% in the dugout tunnel of coal mine.

Sensing and Monitoring of Underground Rock Permeation Damage Using Musicalized MAE GMM Analysis

Moisture could promote the crack propagation in underground rock and increase the accident risk. It is of great significant to sense the moisture permeation state in real time. In this research, a GMM (Gaussian Mixed Model) analysis of musicalized MAE (Modal Acoustic Emission) method for moisture permeation monitoring of layered rock was proposed. First, the effective AW (A Wave) component was extracted by means of frequency decomposition. Then, the envelope was sparsely sampled through musicalized model. The MAE was encoded into 4 musicalized indicators to compress the data with high fidelity. Further, GMM was used to fit MAE parameters. The moisture permeation was evaluated by the signal correlation and the reliability theory. Numerical simulation and experiment demonstrated that moisture could affect the MAE ware. The proposed method could process the monitoring data and evaluate the moisture permeation levels. The continuous MAE signal could be converted into discrete data, which only requires little storage resources. Thus, it is meaningful in the narrow and harsh underground environment.

Flow field and erosion characteristics of the valve head of a vertical well inclinometer

During the drilling, the flow field characteristics of the vertical well inclinometer are complex. In a harsh underground environment, the valve head is prone to erode and wear. To overcome these disadvantages, the three-dimensional (3D) model of the valve head of a vertical well inclinometer was developed, and the flow field and erosion characteristics were simulated by using a numerical program. Results show that the maximum velocity and the maximum turbulence effect occur at the throttling inlet through which the drilling fluid passes the guide sleeve. By analyzing the particle trajectory of the discrete phase model, it is found that the particles above the valve head surface have obvious accumulation and rebound phenomena and that the erosion effect appears to some extent on the valve head surface. Analysis of the shear stress on the surface of the valve head shows that the stress concentration occurs in the valve head directly impacted by the drilling fluid and in the groove of the flow drilling fluid, respectively. The feasibility and accuracy of the simulation are verified by comparing the theoretical results with that of the field test. This investigation can be used to explain the failure of the valve head of the vertical well inclinometer and provide the design and optimization of the valve head with scientific support.

Integrated three-dimensional visualization and soft-sensing system for underground paste backfilling

Cemented paste backfilling (CPB) has attracted worldwide attention because of its advantages in the processing of waste tailings and underground goafs. A problem of the underground CPB procedure that has received little attention is the shortage of devices or techniques for monitoring the real-time backfilling process accurately due to the harsh underground environment. Imprecise information of the backfilling progress will mislead the operators to make improper decisions, such as not pausing the transport system promptly or tuning the ratio of cement to tailings incorrectly. This study proposes a 3D visualization and soft-sensing system for the cemented paste backfilling process. By employing a GeoSLAM ZEB-HORIZON laser scanner to scan the 3D model of the underground goaf, the system estimates the backfilling height in real-time according to the accumulated volume of filled paste and simulates the backfilling of the underground goaf on web pages. In a real Copper Mine, we examined the developed system and soft-sensing technique in goafs and found that the relative error of estimated backfilling height is under 10%, which is acceptable in real production. The results indicate that the developed backfilling visualization and the soft-sensing techniques provide significant guidance for production management in underground backfilling.

Research on attitude monitoring method of advanced hydraulic support based on multi-sensor fusion

The fusion technology of wide-angle ultrasonic sensor and inclination sensor is applied to the attitude monitoring of advanced hydraulic support in the harsh underground environment. Firstly, the measurement model based on the kinematics of advanced hydraulic support is established, and then the calculation algorithm of yaw angle and roll angle based on ultrasonic ranging data is proposed. Finally, the platform of attitude monitoring system is built to realize the attitude monitoring of advanced hydraulic support based on multi-sensor. The field test results show that the maximum root mean square error of distance measurement is 4.36 mm; the maximum root mean square error of the roll angle is 0.12°; the maximum root mean square error of the yaw angle is 0.20°. The test results verify the accuracy and stability of attitude monitoring system experimental platform for the advanced hydraulic support.

Safety Monitoring System in Minimg Environment Using Iot

The average mine worker is exposed to the harsh underground environment which can sometimes cause an injury or loss of life. The older methods of mine condition monitoring involved using a person to go down and report back. This method is however dangerous as the person who is monitoring a specific hazard could be harmed by that hazard. This standard can be reinforced through the implementation of modern technology which is central to the non-invasive mine safety system with wireless sensor networks to obtain the best possible result.

The Design of Improved Optical Fibre Instrumented Rockbolts

Developing an improved understanding of the interaction between the immediate roof and the rockbolts is fundamental in obtaining an effective roof support system. Effective instrumentation along the full length of fully grouted rock bolts would provide the required understanding, which in turn could improve the rock related safety in the underground mines. The rock bolt sensing technology has rapidly developed in the last decade, where the instrumentation has changed from short electrical strain gauges to optical strain and shape sensing using more than 2 slots (which used to be the standard). In addition, the instrumentation has been increased from two orthogonal slots to three or four. With these recent advances of the technologies, there lies a challenge in analysing and understanding the new type of data and in effectively adopting the new technology into the underground mines. This paper deals with the challenges of instrumenting rock bolts with fibre optics and presents techniques for improving the existing technology. Furthermore, it includes a prototype design for an effective implementation of this technology to better suit the harsh underground environment.

Laser Beams-Based Localization Methods for Boom-Type Roadheader Using Underground Camera Non-Uniform Blur Model

The efficiency of automatic underground tunneling is significantly depends on the localization accuracy and reliable for the Boom-type roadheader. In comparison with other underground equipment positioning methods, vision-based measurement has gained attention for its advantages of non-contact and no accumulated error. However, the harsh underground environment, especially the geometric errors brought by the vibration of the machine body to the underground camera model, has a certain influence on the accuracy and stability for the vision-based underground localization. In this paper, a laser beams-based localization methods for the machine body of Boom-type roadheader is presented, which can tackle the dense-dust, low illumination environment with the stray lights interference. Taking mining vibration into consideration, an underground camera non-uniform blur model that incorporate the two-layer glasses refraction effect was established to eliminate vibration errors. The blur model explicitly reveals the change of imaging optical path under the influence of vibration and double layer explosion-proof glass. On the basis of this, the underground laser beams extraction and positioning are presents, which is with well environmental adaptability, and the improved 2P3L (two-points-three-lines) localization model from line correspondences are developed. Experimental evaluation are designed to verify the performance of the proposed method, and the deblurring algorithm is investigated and evaluated. The results show that the proposed methods is effective to restore the blurred laser beams image that caused by the vibration, and can meet the precision need of roadheader body localization for roadway construction in coal mine.

Interview

Zongda Hu from the Chinese Academy of Sciences, China, talks to Electronics Letters about his paper ‘Highly sensitive resonant pressure sensor based on mode-localization effect’, page 882. Zongda Hu My field of research is concerned with Micro-Electro-Mechanical System (MEMS) including pressure sensor, accelerometer, gyroscope, and so on. As we all know, MEMS sensors have different advantages with low-power consumption, small volume, and low price in contrast with traditional sensors. I started working in this field whilst pursuing my master's degree in 2012. My tutor, Professor Yu, who has already worked in this field for almost 30 years guides me in this novel area. I appreciate it so much. The most interesting issue is developing a perfect sensor with high sensitivity, high resolution, and long-term stability. The exploration of petroleum and gas resources is the particular application which interests me as the harsh underground environment requires more reliable MEMS sensors. The exploration of petroleum needs pressure sensors to detect the pressure value in the drilling well. By measuring the gradient, the pressure values at different depths in the well can be accurately grasped. The distribution of petroleum is surveyed by measurement. We are aiming to obtain a more sensitive pressure sensor with high signal-to-noise ratio and large dynamic in contrast with traditional sensors which have insufficient precision. We proposed a novel resonant pressure sensor with two mechanically-coupled resonators. We use the amplitude ratios as the readout for the mode-localized sensors, which is different from the traditional resonant sensors using frequency readouts. The measured result shows that the relative sensitivity is two orders higher than traditional resonant sensors. Mode-localization effects which we used in our resonant pressure sensor, can enhance sensitivity greatly in any resonant sensors. This is expected to lead to high resolution, which will minimize the noise impact of the interface circuit. The amplitude-related metrics, such as amplitude ratios, are generally elected as the readout for the mode-localized sensors which is different from the traditional resonant sensors using frequency readouts. However, linear sensing across the veering point is still under investigation due to the inherent loci veering phenomenon. We have to choose a linear sensing range of the amplitude ratios in order to adapt a linear interface circuit system. The mode-localization effect developed in the present research is likely to have a broad technological impact. The present resonant sensor is not famous for its precision, but for its long-term stability. The sensitivity enhanced by mode-localization effect is a key to break the shackles on resonant sensors. The higher the sensitivity of the sensor is, the smaller the effect of circuit noise should be. We can obtain ultra-resolution resonant sensor through this method. In the long term, mode-localization detection method is expected to grow rapidly. Methods based on mode-localization effect have exploded in popularity and real world applications using this method are one of the most recent major breakthrough in some areas, including geological exploration, aerospace, and military industry. As we all know, the temperature in the Earth's crust can reach higher than 200 degrees Celsius. Thermal stress and thermal expansion in normal resonators will cause great measurement deviations. We are planning to focus on designing a micro-mechanical resonator structure that can release thermal stress extremely effectively. Besides, we also take aluminium nitride material into consideration for its good temperature characteristic. Such resonator systems will have sufficient robustness in such a high temperature environment. The current developed trend of MEMS technology is expected to the foreseeable future. This will open up new applications in fields such as the pressure sensor in our cell phone, the accelerometer in the airbags of our cars, and gyroscopes in drone. However, production of MEMS sensors according to design specifications is extremely difficult because the limitations in manufacturing conditions will result in inconsistencies with predictable design. In addition, integrating sensors and circuits is still a big challenge for industrialisation. But I believe that MEMS technology will be the cornerstone for the development of all walks of life in the future.

The Solution of the Overvoltage Damage for IMS’s Microseismic Monitoring System

With the further development of digitized mine system construction, various kinds of communication，information，automatic and intelligent electronic equipment are widely used in mines. Due to the harsh underground environment of domestic (China) mines, various faults of electronic equipment occur frequently, such as dampness, dust pollution, burn damage, mechanical damage. This makes the system can not run stably and reliably. Especially the phenomenon of burning damage of electronic equipment. It is often large area damage when it happens, which seriously affects the safety production of enterprises. The IMS equipment of microseismic monitoring system that installed in Shizhuyuan Mine was burning damaged many times. Through the in-depth analysis and diagnosis of the failure of the IMS burning module and the overall microseismic monitoring system underground chamber, the fault (which is the system overvoltage) and its causes are found out. According to the reality condition of Shizhuyuan mine that how to prevent the overvoltage damage is systematic analysis and improvement. Than adopt effective measure and methods such as: prevention of overvoltage generation, cut off the intrusion pathway of overvoltage, choosing the surge protector reasonably with the insulation level of the system, switch to the right power supply plan and power supply facilities. These protective measures and methods comprehensively protect the safety of microseismic monitoring system equipment. After that, the microseismic monitoring system is successfully protected and no longer burned down. It successfully solves the problem of equipment burning damage of microseismic monitoring system, provides reliable guarantee for mine safety production. Shizhuyuan mine is a typical underground mining metal ore in China, the successfully solution of overvoltage damage provides a good demonstration for how to prevent mine electronic equipment underground from burning damage, It also provides more standardized and accurate requirements for the way and the protection of power supply system, and the laying of lines for a new projects.

Electrokinetic nanoparticle injection for remediating leaks in oil well cement

This paper presents experimental results on injecting nanoparticles into a hardened oil well cement with electromigration technique. Oil well cement is a special cement type used in underground constructions to protect steel casing of oil wells, CO2 storage wells or oil and gas platforms. Due to the technological reasons, the hardened cement is characterized with a high initial porosity. Further distressing and fracturing occurs in the hardened cement originating from the harsh underground environment which includes elevated pressure and temperature. This leads to severe leakages of the stored media and puts the steel casing to the risk of corrosion.The paper proposes to use a non-destructive remediation technique for the cement repair based on the electrokinetic injection of nanoparticles into the pore and crack space in the material. It shows the efficiency of the technique and presents results from injections with a variety of differently sized nanosilica, microsilica and nanoalumina particles. Characterization of the treated samples was based on microscopy observations, electrical measurements, the change in their open porosity and nanopore surface area assessed by the BET technique. It was found that the electrokinetic process and driving of particles in samples is very efficient and reduces the sample porosity by about 4–7% with respect to the initial porosity of intact specimens and 5–8% on aged samples. The BET analysis confirmed reduction of the inner pore surface area in the treated samples. Increasing level of agglomeration of particles on the surface as well as in the inner pores was observed during electrokinetic treatment and documented with the electric current measurements.

A Fiber Bragg Grating-Based Monitoring System for Roof Safety Control in Underground Coal Mining.

Monitoring of roof activity is a primary measure adopted in the prevention of roof collapse accidents and functions to optimize and support the design of roadways in underground coalmines. However, traditional monitoring measures, such as using mechanical extensometers or electronic gauges, either require arduous underground labor or cannot function properly in the harsh underground environment. Therefore, in this paper, in order to break through this technological barrier, a novel monitoring system for roof safety control in underground coal mining, using fiber Bragg grating (FBG) material as a perceived element and transmission medium, has been developed. Compared with traditional monitoring equipment, the developed, novel monitoring system has the advantages of providing accurate, reliable, and continuous online monitoring of roof activities in underground coal mining. This is expected to further enable the prevention of catastrophic roof collapse accidents. The system has been successfully implemented at a deep hazardous roadway in Zhuji Coal Mine, China. Monitoring results from the study site have demonstrated the advantages of FBG-based sensors over traditional monitoring approaches. The dynamic impacts of progressive face advance on roof displacement and stress have been accurately captured by the novel roadway roof activity and safety monitoring system, which provided essential references for roadway support and design of the mine.

Novel wireless channels characterization model for underground mines

The propagation characteristics of electromagnetic waves in underground mines are different from those in free space because of the harsh underground environment. Physical phenomena like severe reflection, scattering, and diffraction along the mines’ rough walls will affect the propagation of electromagnetic waves. Channel predictions are crucial for reliable and optimal wireless communication in an underground environment. Although there are several channel prediction techniques, most of them are very difficult and time consuming. This work presents a new approach in wireless channel modeling in underground mines. The model is generated by adopting a performance-based approach rather than classical coverage-based approach. This new model, called “Mine Segmenting Wireless Channel Model”, divides the mine area into three main segments: (1) Line-of-Sight (LOS), (2) Partial-Line-Of-Sight (PLOS) and (3) Non-Line-Of-Sight (NLOS). We examine the impact of topology on performance of 802.11b system with Rician/Rayleigh fading.The model is statistically verified using simulations and is applied to fading wireless local area networks channel for IEEE 802.11 applications. Finally, the communication performance of a realistic IEEE 802.11b signal is evaluated in a real underground mine gallery (NORCAT Mine, Sudbury, Ontario, Canada). The results of the actual experiment were very similar to that of the model simulation.

Development of a very low-frequency electromagnetic sonde for the measurement of settlement through rock and mining backfill

A prototype sonde has been developed to establish whether distance and, hence, movement can be measured over short ranges by the use of low-frequency electromagnetic fields. An initial trial under laboratory conditions demonstrated that the principle could be used for measurements through air, though the measurements were affected by temperature and by vehicle movements outside the laboratory. Subsequent field trials at an abandoned mine produced measurements through up to 20 m of rock that were very close to the surveyed distances. Finally, a two-week trial of settlement monitoring undertaken in a roadway in the harsh underground environment of Boulby salt and potash mine confirmed the potential of the technique for accurate measurement of convergence and separation. Further tests of the ability of the sonde to measure settlement through fill are now planned.