Underground Environment Research Articles

OPTILOD: Optimal Beacon Placement for High-Accuracy Indoor Localization of Drones.

For many applications, drones are required to operate entirely or partially autonomously. In order to fly completely or partially on their own, drones need to access location services for navigation commands. While using the Global Positioning System (GPS) is an obvious choice, GPS is not always available, can be spoofed or jammed, and is highly error-prone for indoor and underground environments. The ranging method using beacons is one of the most popular methods for localization, especially for indoor environments. In general, the localization error in this class is due to two factors: the ranging error, and the error induced by the relative geometry between the beacons and the target object to be localized. This paper proposes OPTILOD (Optimal Beacon Placement for High-Accuracy Indoor Localization of Drones), an optimization algorithm for the optimal placement of beacons deployed in three-dimensional indoor environments. OPTILOD leverages advances in evolutionary algorithms to compute the minimum number of beacons and their optimal placement, thereby minimizing the localization error. These problems belong to the Mixed Integer Programming (MIP) class and are both considered NP-hard. Despite this, OPTILOD can provide multiple optimal beacon configurations that minimize the localization error and the number of deployed beacons concurrently and efficiently.

An adaptive evacuation system for the Gran Sasso underground laboratory

The Gran Sasso National Laboratory (LNGS) is, at present, the largest deep underground laboratory in operation for astroparticle physics and rare event research. The LNGS was created to carry out this research exploiting an overburden of 1,400 m of rock to reduce the flux of muons from cosmic rays. Operating an underground laboratory and its facilities implies a high level of risk. To mitigate risks at the LNGS, a crucial aspect is represented by the evacuation of people from an underground environment during emergencies. The connection between the underground facilities and the outside infrastructure is limited, and the intervention by rescue teams is complicated. This paper reports the study of an adaptive evacuation system to improve the evacuation performance in underground laboratories. The system proposed is composed of a combination of passive, dynamic, and adaptive signage that is able to adapt itself to lead the laboratory occupants to the safe location for evacuation (assembly point). The system collects information from all safety plants, and the data are processed using a customized path-finding algorithm. In the computational algorithm, the underground laboratory is represented as a grid, and the customized path-finding algorithm discovers all available paths to reach the identified evacuation assembly point.

Research on the dust-control technology of a double-wall attached-ring air curtain on an excavation face.

On the basis of the jet theory of airflow fields and the gas-solid two-phase flow theory, we studied the law of dust migration in a simulated dusting space. We used the control variable method and numerical simulation software to explore the airflow field and dust concentration distribution on the working surface of the dusting under different inlet wind speeds and different attached blades of the double-walled annular air curtain. We determined the speed of the inlet of the annular air curtain to be 30 m/s. When the angle of the attached blade was 30°, the dust concentration of the driver and other workers was controlled below 100 mg/m3, which produced the best dust control effect is the best. Using real data, we built a similar test platform to test the airflow field and dust concentration. Through data measurement and analysis, we proved that a dust control system with a double-wall attached-ring air curtain formed a circulating airflow field that could shield dust and effectively reduce dust concentration in the simulated space. The dust removal efficiency of total dust and exhaled dust reached 98.5% and 97.5%, respectively. We compared the test data and simulation results and concluded that the double-wall attached-ring air curtain could effectively ensure the safety of mine production and provide a better underground working environment for operators.

Nuclear Physics Mid Term Plan at LNGS

The Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali del Gran Sasso (LNGS) is one of the largest underground physics laboratory, a very peculiar environment suited for experiments in Astroparticle Physics, Nuclear Physics and Fundamental Symmetries. The newly established Bellotti Ion Beam facility represents a major advance in the possibilities of studying nuclear processes in an underground environment. A workshop was organized at LNGS in the framework of the Nuclear Physics Mid Term Plan in Italy, an initiative of the Nuclear Physics Division of the Instituto Nazionale di Fisica Nucleare to discuss the opportunities that will be possible to study in the near future by employing state-of-the-art detection systems. In this report, a detailed discussion of the outcome of the workshop is presented.

Intelligent management of carbon emissions of urban domestic sewage based on the Internet of Things

Domestic wastewater is one of the major carbon sources that cannot be ignored by human society. Against the background of carbon peaking & carbon neutrality (Double Carbon) goals, the continuous urbanization has put heavy pressure on urban drainage systems. Nevertheless, the complex subjective and objective conditions of drainage systems restrict the field monitoring, measurement, and analysis of drainage systems, which has become a great obstacle to the study of carbon emissions from drainage system. In this paper, 3389 sensor terminals of Internet of Things (IoT) are used to build a field monitoring IoT for urban domestic wastewater methane (CH4) carbon emission, with 21 main districts of Chongqing Municipality in China as the study area. Incorporating Fick's law of diffusion, this field monitoring IoT derives a measurement model for methane carbon emissions based on measured concentrations, and solves the problems of long-term and stable monitoring and measurement of methane gas in complex underground environment. With GIS spatio-temporal analysis used to analyze the spatial and temporal evolution patterns of carbon emissions from septic tanks in drainage systems, it successfully reveals the spatial and temporal distribution of methane carbon emissions from drainage systems in different seasons, as well as the relationship between methane carbon emissions from drainage systems and the latitude of direct sunlight. Applying the DTW method, it quantifies the stability of methane monitoring in drainage systems and evaluates the effects of Sampling Frequency (SF) and Number of Devices Terminal (NDT) on the stability of methane monitoring. Consequently, an intelligent management system for carbon emissions from urban domestic wastewater is constructed on the base of IoT, which integrates methane monitoring, measurement and analysis in septic tanks of drainage systems.

Analysis of Mineralization and Disease Characteristics of Bronzes Unearthed in Archaeology

Bronze artifacts unearthed by archaeologists are affected by underground burial environment and other factors, and most of them have different degrees of corrosion. Bronze artifacts unearthed by archaeologists have different degrees of mineralization. Establishing a data analysis database for basic structure and disease analysis of mineralized bronze artifacts is a necessary prerequisite for developing targeted reinforcement materials and realizing accurate protection. Based on the characteristic analysis of the mineralized bronzes, this paper systematically analyzed the mineralization and disease characteristics of the mineralized bronzes by Confocal Super Depth-of-Field Microscope(CSDTM), scanning electron microscopy (SEM), energy spectrum analysis(EDS) and XRD, and compared and analyzed the microscopic morphology, composition and phase structure of the bronzes under the same burial environment, so as to provide support for subsequent targeted protection and reinforcement.

LIVER: A Tightly Coupled LiDAR-Inertial-Visual State Estimator With High Robustness for Underground Environments

LIVER: A Tightly Coupled LiDAR-Inertial-Visual State Estimator With High Robustness for Underground Environments

Image Recognition of Mine Water Inrush Based on Bilinear Convolutional Neural Network with Few-Shot Learning.

With the increasingly widespread application of deep learning technology in the field of coal mines, the image recognition of mine water inrush has become a hot research topic. Underground environments are complex, and images have a high noise and low brightness. Additionally, mine water inrush is accidental, and few actual image samples are available. Therefore, this paper proposes an algorithm that recognizes mine water inrush images based on few-shot deep learning. According to the characteristics of images with coal wall water seepage, a bilinear neural network was used to extract the image features and enhance the network's fine-grained image recognition. First, features were extracted using a bilinear convolutional neural network. Second, the network was pre-trained based on cosine similarity. Finally, the network was fine-tuned for the predicted image. For single-line feature extraction, the method is compared with big data and few-shot learning. According to the experimental results, the recognition rate reaches 95.2% for few-shot learning based on a bilinear neural network, thus demonstrating its effectiveness.

Pore Structure Evolution and Failure Mechanism of Limestone in the Taiyuan Formation of the Ordos Basin under High Temperature.

The study on the destruction of the limestone microstructure after high-temperature treatment has a significant value in the airtightness and safety of underground high-temperature geotechnical engineering. In order to truly simulate the influence of the underground high-temperature environment on limestone, taking seven groups of limestones of the Taiyuan Formation in the Ordos Basin as examples, we carried out a high-temperature (25-1200 °C) heating experiment of limestone in an argon atmosphere. The pore structure of limestone after the high temperature is studied based on scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), porosity, and permeability, and the change in the fractal dimension of the limestone pore structure was discussed based on the thermodynamic fractal theory, combined with X-ray diffraction (XRD) and thermogravimetry differential scanning calorimetry (TG-DSC), the variation of mineral composition with temperature is characterized, and the evolution mechanism of the limestone microstructure under high temperature is discussed. The results show that the evaporation of pore water does not destroy the lattice structure of limestone minerals; however, with the increase of temperature, the complete decomposition of dolomite and calcite occurs, along with the tensile fracture of calcite crystals under the effect of swelling stress. Moreover, the new minerals generated by the decomposition products under the effect of temperature severely damage the crystal structure, leading to the rapid increase of porosity and permeability. The comprehensive results show that the decomposition, expansion, and recrystallization of calcite and dolomite minerals after 800 °C led to the development of limestone macropores and fissures, increased the pore throat radius, enhanced the pore connectivity, simplified the pore structure, and sharply increased the permeability; thus, 800 °C can be used as the critical temperature to change the limestone pores and fractures. The research results can provide data support for subsurface high-temperature geotechnical engineering.

Comprehensive heat extraction performance and fractured reservoir cooling effect analysis of a novel mine enhanced geothermal system

Mining deep metal mines poses significant challenges due to the high-temperature conditions in such environments. However, the vast untapped geothermal energy within these mines holds great prospects for development and application. Herein, we proposed a novel technology for the deep mine cooling and enhanced geothermal system (DMC-EGS), which transforms the relationship between deep mining and geothermal resources from a source of heat harm to heat benefit, while also providing conditions for underground mining environment cooling. Understanding the fluid flow and heat transfer processes in the deep mine thermal reservoir is crucial for developing DMC-EGS. Based on the local thermal equilibrium theory, a three-dimensional thermal–hydraulic coupled model of the thermal reservoir in the Sanshan Island Mine containing multiple fractures was established. The impact of natural fractures and fracture number on the thermal recovery performance and cooling effect of the system was considered, and the optimization scheme of heat recovery wellbore was proposed for the deep thermal reservoir of Sanshan Island Mine. It can be found that fractures play a crucial role in fluid-rock heat exchange. Compared with scenarios without fractures, hydraulic fractures could significantly improve the heat transfer capacity and rock cooling effect, resulting in a 45.7% increase in the amplitude of rock matrix temperature decrease and more than a 1.76-fold increase in overall heat recovery efficiency. In addition, the number of fractures significantly impacted the temperature distribution within the rock formation, and an increased number of fractures was associated with more efficient heat recovery performance. When the number of fractures was 7, the cumulative thermal production could reach 6.767 × 109 J. Among the three thermal exploitation schemes compared, the DMC-EGS under the triple-well mode yielded the best heat recovery performance during the 40-year extraction period, superior to the conventional dual-well mode, while the one injection and two production mode demonstrated better heat recovery capacity and cooling effect.

A high resolution detection approach combining probe drilling and horizontal cross-hole resistivity tomography to interpret water conducting channels ahead of the tunnel: A case study in Yunnan, China

The geological conditions in Yunnan Province, China, are intricate, and numerous challenges are anticipated during tunnel excavation. The goal of this study was to develop a high resolution detection approach combining probe drilling and horizontal cross-hole resistivity tomography to interpret water conducting channels ahead of the tunnel. A complex section of the Xianglu Mountain tunnel was taken as an example. Drilling data from 10 boreholes are used to establish the initial resistivity model ahead of the tunnel face. The utilization of drilling data as a priori information refines the horizontal cross-borehole resistivity tomography imaging results, providing a more accurate depiction of the subsurface conditions. In practical applications, the use of multiple boreholes for high resolution detection via probe drilling analysis and horizontal cross-hole resistivity tomography is relatively uncommon in complex underground environments and represents an engineering innovation. At the Xianglu Mountain tunnel site, 13 electrical resistivity tomography (ERT) profiles were executed to thoroughly assess the geological conditions. A 3-D resistivity model was constructed via interpolation of this dataset. The 3-D resistivity model not only facilitated precise estimation of the 3-D hydrogeological environment at the Xianglu Mountain tunnel site but also enhanced the accuracy of identifying the water conducting channels by revealing low-resistivity interconnected zones. This approach offers a precise guide for determining the location of the critical water conducting channels and for optimizing grouting treatment strategies based on the characterization, geometry, resistivity spatial distribution, and hydrogeological conditions of the studied zones. The acquired results, which are in good accordance with the reality of the studied area in terms of locating the water conducting channels, can be utilized to develop preventative techniques for water and mud inrush disasters during tunnel construction.

Borehole Depth Recognition Based on Improved YOLOX Detection

Abstract This study proposes a method for recognizing the drill depth in low-light underground environments, with the aim of addressing the issues of low efficiency and susceptibility to manual changes in the current methods. The method is based on an improved You Only Look Once X model. Initially, image data undergo enhancement and annotation. Secondly, it incorporates an attention mechanism to improve the feature extraction capability. The feature pyramid is utilized to minimize feature loss and facilitate better multi-scale feature fusion. Additionally, the loss function is optimized to enhance the localization ability of the prediction box. The enhanced model achieves an accuracy of 91.3$\%$, representing a 4.4$\%$ increase compared to the pre-improvement performance, and demonstrates improved positioning accuracy. Successful drilling depth measurements were carried out with the acquired positioning information.

DNA taxonomy reveals high species diversity among the stygobiont genus Metastenasellus (Crustacea, Isopoda) in African groundwater

This study aimed to explore the species diversity within the isopod genus Metastenasellus in Benin and Cameroon. Compared to other parts of the world, the described diversity of stygobiotic crustaceans in Africa is low due to a dearth of studies and taxonomic expertise. However, recent research activities in Benin and Cameroon suggest higher groundwater diversity than previously envisioned. Recent sampling campaigns in these countries have shown that Metastenasellus is a major group in the underground aquatic environment. The accumulation of biological material provided an opportunity to explore species diversity within the genus using a DNA taxonomy approach based on the cytochrome c oxidase subunit I (COI) gene fragment. Despite the limitations of using a single-locus approach for species delimitation, an overview of the diversity within the genus Metastenasellus was obtained, revealing the presence of 23 distinct lineages. Several elements suggest that most, if not all, of these lineages represent valid species. These include high genetic distances between lineages, morphologically distinct species separated by genetic distances of the same order of magnitude as between other described lineages, and the coexistence of different lineages at the same stations. Despite a limited sampling effort, these first results indicate a high level of species diversity and endemism within Metastenasellus in the studied regions. The narrow geographic distribution of the lineages suggests strong isolation and limited dispersal abilities. This study highlights the potential for discovering a significant number of new species within this genus and emphasizes the need for further research to uncover the extent of diversity in African stygobiotic isopods.

Characterization and Environmental Risk Assessment of Coal-based Solid Waste Towards Underground Backfilling

This study evaluated the feasibility of coal-based solid waste as a subsurface fill material based on its physicochemical properties and potential environmental risks. The results show that the special physical structure and the chemical composition of coal-based solid wastes are advantageous as filling materials. In terms of physical structure, the spheres improve the flowability and mixing homogeneity of the mixture, while lumps give stabilizing support; the special chemical compositions also improve the strength, durability and corrosion resistance of the filler. The contents of Cd, As, Cr, Cu, Ni and Co in coal-based solid waste are less directly harmful to the environment, but arsenic showed a relatively strong enrichment. Cd in coal gangue and desulfurized gypsum were medium or very high risk due to strong migration and bioavailability, respectively, while Co in desulfurized gypsum present a medium risk. Both coal gangue and desulfurized gypsum may contaminate the underground environment, the other materials pose less threat to the environmental. In engineering applications, attention should be paid to the main contaminant As, as well as Cd and Co because of their mobility and high bioactive fraction, to reduce potential environmental risk.

Detection of Underground Dangerous Area Based on Improving YOLOV8

In order to improve the safety needs of personnel in the dark environment under the well, this article adopts the improved YOLOV8 algorithm combined with the ray method to determine whether underground personnel are entering dangerous areas and to provide early warning. First of all, this article introduces the coordinate attention mechanism on the basis of YOLOV8 target detection so that the model pays attention to the location information of the target area so as to improve the detection accuracy of obstruction and small target areas. In addition, the Soft-Non-Maximum Suppression (SNMS) module is introduced to further improve accuracy. The improved model is then combined with the ray method to be deployed and applied under a variety of angles and different scenic information cameras. The experimental results show that the proposed method obtains 99.5% of the identification accuracy and a frame speed of 45 Frames Per Second (FPS) on the self-built dataset. Compared with the YOLOV8 model, it has a higher accuracy and can effectively cope with the changes and interference factors in the underground environment. Further, it meets the requirements for real-time testing in dangerous underground areas.

Application of a Hot Melt Recoverable Anchor Cable in Foundation Pit Support

With the continuous development of the social economy, the depth of foundation pit excavation of proposed construction projects in various places gradually increases, which is closer to the building red line, and the surrounding environment is relatively complex; therefore, there are few supporting schemes for foundation pit selection. Based on the Vanke B-6 plot of a real estate development project, the project has close neighboring buildings. If we use a normal anchor cable, underground cut line problems are possible, and so we choose the hot melt-type recoverable anchor; with three element dispersion pressure, the anchor cable can minimize broken sections of brush slope excavation and has advantages of a simplified construction process and good seismic performance. Except for the cable barrel, the other parts and all steel strands can be recycled, and recycled parts can be reused. The recyclable bolt (cable) overcomes the disadvantages of the conventional bolt (cable) as a temporary support, such as pollution of the underground environment, encroachment on the underground space of adjacent buildings, and becoming an underground obstacle in follow-up projects. It accords with the characteristics of the times of environmental protection and sustainable development, and has achieved good economic and social benefits.

A comprehensive study on applications of nanomaterials in petroleum upstream and downstream industry.

Nanotechnology has emerged as a revolutionary technology that has been applied in the oil and gas industry for over a decade, spanning the upstream, midstream, and downstream sectors. Nanotechnology has made significant contributions to the exploration of crude oil and natural gas, both in underground and deep-water environments. It has also played a crucial role in improving the drilling process, enabling the extraction of oil and gas resources from beneath the Earth's surface. Nanoparticles, with their unique physical and chemical properties, such as high specific surface area, high pore volume, and small size, have demonstrated considerable potential in the oil industry. Extensive research has been conducted to explore various types of nanoparticles for advanced applications, including oil exploration, drilling, production, and enhanced oil recovery (EOR). Moreover, nanomaterials have found applications in downstream and intermediate sectors, such as crude oil refining, natural gas processing, and transportation and storage of petroleum products. Ongoing advancements in nanomaterial synthesis methods, the exploration of new nanomaterial uses, and understanding the remarkable properties of nanomaterials will continue to make them increasingly valuable in the oil and gas sector. The oil and gas industry recognises the potential of nanotechnology and nanoparticles and is investing significantly in research and development in this area. This comprehensive review aims to summarise successful applications of nanotechnology while addressing associated challenges. It serves as a valuable resource for future research and application endeavours in the field, highlighting the potential of nanotechnology in the oil and gas industry.

Bioinspired Whisker Sensor for 3D Mapping of Underground Mining Environments.

Traversing through challenging, unstructured environments, particularly in mining scenarios characterized by dust concentration, darkness, and lack of communication presents formidable obstacles for traditional sensing technologies. Drawing inspiration from naked mole rats, characterized as being skilled subterranean navigators that depend heavily on touch to navigate their environment, this study introduces a new whisker-sensing disk designed for 3D mapping in unstructured environments. The disk comprises a circular array of 32 whisker sensors, each featuring a slender flexible plastic rod attached to a compliant base housing a 3D Hall-effect sensor. The whisker sensor is modeled using both analytical and data-driven approaches to predict rotation angles based on magnetic field measurements. The validation and comparison of both models are performed by evaluating data from other whisker sensors. Additionally, a series of experiments demonstrates the whisker disk's capability in performing 3D-mapping tasks, along with successful implementation on diverse robotic platforms, highlighting its future potential for effective 3D mapping in complex and unstructured subterranean environments.

Path planning for unmanned load–haul–dump machines based on a VHF_A* algorithm

This study aimed to address the low search efficiency, long planning time, and unsmooth path problems in narrow and curved underground mining cave environments using traditional path planning algorithms. Thus, a new path planning method (VFH_A *) based on VFA and A* is proposed for unmanned load–haul–dump (LHD) operating in underground mines. First, the trajectory of the LHD articulation point is considered, the nodes are extended using this point, and collision detection is performed. Notably, the extended nodes neither collide nor conform to the trajectory of the LHD. Second, the vector field histogram (VFH) algorithm is introduced, and the steering and collision threat costs are combined with the comprehensive cost function of the traditional A* algorithm to form the VFH_A* algorithm. Thus, the node with the lowest comprehensive cost is selected for expansion, and redundant nodes are eliminated from the searched node paths. Third, the path is smoothed via Bezier interpolation. This ensures that the LHD operates smoothly and prevents excessive changes in the articulation angle. The proposed method was evaluated using above-ground and underground simulations. Compared with A* and GA algorithms, the VFH_A* algorithm significantly improved the search efficiency and can efficiently generate safe and smooth task paths in different scenarios. The planning time for each scenario was reduced by 85%. Finally, tracking experiments were conducted on the planned task paths of 1.5 and 2.5 m/s, indicating that the tracking error was less than 0.23 m. Overall, the planned path meets the requirements of unmanned LHD, indicating that the proposed method can adapt to practical applications.

Ventilation characteristics of double-forced air pipe ventilation in comprehensive mechanized excavation face and determination of its optimal parameters

ABSTRACT This study proposes a ventilation and dust control approach using double-forced air pipes at the tunnel excavation face, aiming to optimize the dust control and reduction measures for underground coal mining environment. We designed a physical model in proportion to the 11,139 excavation face in the Zhangji Coal Mine of China Huaihe Energy Holding Group Coal Company. To begin with, CFD numerical simulation was employed to unveil the basic laws of the double-forced air pipe ventilation approach, including airflow characteristics and dust concentrations. The orthogonal experimental method was then adopted to analyze the influence mechanism of installation location and airflow ratio of the double pipes on the dust density around the driver’s operating space. Results suggest that the double-forced air pipe ventilation can efficiently improve the airflow velocity at the excavation face, reaching 5.54 m/s. With the minimum dust density around the driver’s operating space as the optimal parameter standard and combined with the R value, the three factors in the orthogonal experiment can be sorted as: the distance between the forced ventilation pipe at the driver’s side and the excavation face (R = 206.91) > the distance between the forced ventilation pipe at the return air side and the excavation face (R = 171.72) > the airflow ratio of the two pipes (R = 77.52). The optimal combination is that the distance between the ventilation pipe at the driver’s side and the excavation face is 5 m, the distance between the ventilation pipe at the return air side and the excavation face is 5 m, and the airflow ratio of the two pipes is 6:4. In such a case, the dust density around the driver’s operating space is 48.21 mg/m3, achieving an ideal dust control effect.