Mine Tunnel Research Articles

Large scale analogue experiments in rock mechanics : new experimental facility, 3D-printed material and insertion of force transducers for stresses measurement.

Abstract The aim of this paper is to present a new experimental device that was designed to perform analogue rock mechanics experiments with 3D-printed material. The device consists in the creation of two rectangular excavations (mining tunnels) in slices of 3D sand printed material. This is a true-triaxial test device that allows us to study the mechanical behaviour of reduced scale models of underground structures. The experimental protocol entails the horizontal loading of the specimen, followed by the excavation of two galleries while the specimen is maintained under a constant load. The results of the test carried out in DiMiTri show a generally logical evolution of the sensors with an increase in vertical stresses induced by the presence of excavations. This paper discusses the upcoming challenges in terms of instrumentation that will be encountered, together with the new opportunities for future research.

A new frequency domain denoising method for coal mine transient electromagnetic measuring data

Abstract Due to limitation of space in mine tunnel, only a 2m × 2m rectangle coil can be employed to collect the electromagnetic signals for the mine transient electromagnetic analysis. Hence, a small emission magnetic moment and weak detection signal strength will increase the electromagnetic analysis difficulty. Moreover, the transient electromagnetic response signal in mines exhibits exponential decay over time, with late-stage amplitudes being notably small, which makes these signals susceptible to noise interference. As a result, it is necessary to study effective noise removal methods to enhance the signal-to-noise ratio of the late-stage electromagnetic data. Addressing this challenge task, this study proposes a new method for frequency domain denoising of transient electromagnetic data. This new method utilizes the Fourier Transform to convert the original transient electromagnetic data from the time domain to the frequency domain, and then, the noise is identified and removed through the frequency characters. Lastly, the processed frequency domain information is transformed to the time domain by the Fourier Inverse Transform to restore the time domain signals. The effect of this frequency domain denoising method is demonstrated through numerical simulations and underground coal mine field data to show significant noise reduction performance on the abnormality detection in the underground coal mine.

Scanning the underground: Comparison of the accuracies of SLAM and static laser scanners in a mine tunnel

Superior measurement speed is a great benefit of Simultaneous Localization and Mapping (SLAM) scanners, especially in enclosed spaces. Here, we (i) provided a workflow for testing both terrestrial static laser scanners and SLAM scanners in underground spaces, which can help to identify the partial components of the error, and (ii) using this workflow, we compared the performance of four SLAM and two terrestrial scanners in a mining environment (120 m long tunnel). Although SLAM scanners suffered from greater noise than static scanners, their performance was excellent, with root mean square deviations after primary georeferencing on control points within the range of 12–24 mm for SLAM and 22–27 mm for static scanners. This result, along with additional provided metrics, suggests that SLAM scanners of the new generation perform excellently in enclosed spaces which, along with their ease of use, makes them highly suitable for measurements in this type of environment.

Mechanical Behaviors of Steel Segment Support Structures for TBM-Excavated Coal Mine Tunnels: Experimental and Numerical Study

Mechanical Behaviors of Steel Segment Support Structures for TBM-Excavated Coal Mine Tunnels: Experimental and Numerical Study

Intrinsically safe DAB converter for reliable power supply in harsh environment via extended phase shift pulse train control

AbstractIn this article, an extended‐phase‐shift‐based pulse train control (EPS‐PT) for an intrinsically safe dual active bridge (DAB) converter is proposed to satisfy the safe and reliable power supply in harsh environments such as gas stations, chemical plants, and mining tunnels in complex power systems. A discrete pulse switching control method is introduced, and the input voltage and output current are sampled to calculate the primary target phase shift angle of the DAB converter, followed by the inner phase shift angle, while the secondary phase shift angle is rapidly adjusted by the voltage feedback. In order to meet the requirements of effective control and safe power supply in harsh environments, the system parameters are designed by comprehensively considering the control performance and intrinsically safe requirements. The simulation and experimental results demonstrate that the proposed DAB converter exhibits rapid dynamic response and intrinsic operation safety.

Simulation and field application study of roadway remodeling load-bearing arch technology

This paper presents a numerical simulation study on the impact of material strength, thickness, and lateral pressure coefficient on the load-bearing arches used in tunnel reconstruction, as well as industrial experiments based on these arches. The study compares three different cross-sectional shapes—straight-wall semicircular arches, flat-bottom straight-wall semicircular arches, and inverted straight-wall semicircular arches—through multi-dimensional numerical simulations investigating various parameters such as material strength, thickness, and lateral pressure coefficient. We analyze the maximum load-bearing capacity of the reconstructed arches and the evolution characteristics of the plastic zones in the tunnel support structures with different cross-sectional shapes. The results indicate that among the factors affecting the ultimate load-bearing capacity of the arches, the ranking is as follows: tensile strength > thickness > lateral pressure coefficient. Additionally, the shape of the cross-section significantly influences the evolution of plastic zones during tunnel failure. The technology of reconstructing load-bearing structures in coal mine tunnels effectively addresses the deformation issues caused by the superimposition of multiple stresses in the tunnels of Daniu Coal Mine. This provides valuable insights for understanding and managing significant deformations resulting from concentrated stresses from in-situ rock, tectonic forces, and mining-induced stresses.

A LESO Based Backstepping Controller Considering Coal Seam Hardness for Rotary Speed in Coal Mine Tunnel Drilling Process

A LESO Based Backstepping Controller Considering Coal Seam Hardness for Rotary Speed in Coal Mine Tunnel Drilling Process

Particle swarm optimization inverse tracing method for mine tunnel fire based on quasi-steady-state heat transfer mechanism

Rapidly locating and assessing fires in coal mines is essential for effective response and minimizing damage. Traditional methods often struggle to swiftly and accurately pinpoint fire locations and statuses. Hence, this study introduces a particle swarm inverse tracing approach based on the quasi-steady-state heat transfer between high-temperature flue gases and mine tunnel walls. This method aims to remotely monitor smoke flow temperatures and gas concentrations to determine fire locations and combustion trends. Validation of the fire source tracing model was conducted through comprehensive tunnel fire experiments and numerical simulations. The particle swarm optimization inverse tracing method yielded a maximum 7.65 % error in fire location determination compared to actual measurements, while accurately matching the measured fire source heat release rate curve. These findings underscore the method’s high precision and reliability, particularly evident during the developmental and stable stages of fire burning.

Inversion of TEM Responses in Tunnel with Steel Infrastructure and Its Application

Steel infrastructure in tunnels significantly affects the accuracy of transient electromagnetic (TEM) data inversion. This study proposes and compares two methods to effectively mitigate this interference: the correction factor method and the prior information constraint method. The correction factor method constructs correction factors using interference data obtained in two ways. The first method, numerical simulation, is theoretically precise but relies heavily on accurate model parameters and requires significant computational resources. The second is conducted by measuring the interference data in the working space. While this approach is simple and operationally convenient, its effectiveness in correction is limited by the measured data quality. The a priori information constraint method improves the inversion by introducing a more accurate initial model. The inversion results of synthetic data indicate that the inversion based on the correction factor method and the prior information constraint method can effectively invert the anomaly. However, the delay effect remains a challenge for the correction factor method. Finally, we invert the field data measured in a mine tunnel by combining the interference processing methods.

Experimental and Numerical Study of Air Flow Reversal Induced by Fire in an Inclined Mine Working

Effective fire prevention in mine workings and tunnels requires a thorough theoretical analysis of the heat and mass transfer processes within these structures. This involves using established models to calculate non-isothermal air flow dynamics in long tunnels and mine workings. While the ventilation of tunnels has been extensively studied, significant challenges persist regarding mine ventilation systems, particularly due to their complex and branched topology. This study aimed to address these challenges and gaps in mine ventilation. We designed a laboratory bench to simulate an inclined mine working with a heat source (fire) and validated a mathematical model of heat and mass transfer in such settings. Using experimental measurements, we verified the model’s accuracy. It is important to note that our experimental and theoretical analyses focused solely on the thermal effects of a fire, without considering the release of harmful impurities. Using the validated model, we conducted multiparameter simulations to identify the conditions leading to the formation of a thermal slug in an inclined mine working and the subsequent reversal of air flow. The simulation data enabled us to determine the dependency of the critical heat release rate on the aerodynamic parameters of the mine working. Additionally, we evaluated the changes in average air density within a mine working at the critical heat release rate. These findings are crucial for the further development of a network-based method to analyze air flow stability in mine ventilation networks during fires.

Studi Uji Kuat Tekan Uniaksial dan Uji Kuat Tarik Tidak Langsung Untuk Menentukan Brittleness Index (BI) Pada Batupasir di Formasi Pulau Balang dan Balikpapan

In the process of designing mine slopes, drilling or tunneling, to determine the level of strength and brittleness factors of rock on a slope, it is necessary to carry out a uniaxial compressive strength test or indirect tensile strength test of the rock. Compressive strength testing is carried out to determine how long the rock maintains its strength or elastic properties when pressure is applied. This data can be used as information to understand the analysis of factors that influence the physical properties of rocks on the compressive strength of rocks from physical properties and compressive strength testing activities. and indirect tensile strength testing is carried out to determine the stress value contained in the rock. To determine the level of rock brittleness, it can be done by comparing the uniaxial compressive strength value and the indirect tensile strength value. This data can be used as information and reference for companies that will design a mine slope, drill and tunnel, how strong the strength and level of brittleness of rocks in areas dominated by sandstone. This research uses quantitative methods, so that to obtain accurate calculation data, testing methods are used in the form of uniaxial compressive strength tests and indirect tensile strength tests, in this case tested on sandstone samples obtained from 2 rock formations including the Pulaubalang formation and the Balikpapan formation, so that accuracy The test result values ​​can be obtained well. And after testing, a comparison is made between the uniaxial compressive strength test value and the indirect tensile strength test to obtain the Brittleness Index value.Based on the observation results, it can be concluded that when the brittleness of the rock becomes greater, the performance of the cutting digger increases several times.

Time‐frequency domain correlation method based on the synchrosqueezed wavelet transform for tunnel vibroseis and its application

AbstractTo meet the demand for long‐distance and highly accurate detection in tunnel construction, a vibroseis source has been introduced into tunnel forward prospecting. However, serious noise in tunnels reduces the resolution of vibroseis signals, and small‐scale structure recognition in tunnels requires higher signal resolution. Thus, we develop a time‐frequency domain correlation method based on the synchrosqueezed wavelet transform for tunnel vibroseis data. Time‐frequency domain correlation may capture more information than a single time or frequency domain correlation method, and its effectiveness depends on the time‐frequency transformation method. The synchrosqueezed wavelet transform allows us to obtain high‐resolution time‐frequency spectra and thus helps to extract high‐resolution effective signals. The advantages and disadvantages of different correlation methods are highlighted using numerical examples, in which the high resolution and strong robustness of the time‐frequency domain correlation method based on the synchrosqueezed wavelet transform are demonstrated. A detailed field case study in an iron mine tunnel further demonstrates the reliability of the time‐frequency domain correlation method based on the synchrosqueezed wavelet transform for practical data.

Study on the Influence of Some Ventilation Parameters on Dust Dispersion in Heading Face Coal Mine Using CFD Numerical Model

Coal dust is one of the environmental factors that seriously affect the health of workers as well as the mining equipment in underground coal mines. At present, coal dust is commonly generated during drilling, blasting, excavation, and transportation processes in mining operations. During mining blasting processes, coal dust is generated with varying particle sizes and high concentration levels. High concentrations of dust will affect mining operations and increase the ventilation time required for mining faces. In addition, coal dust exists in suspended form in the roadway and is harmful to human health, especially fine dust particles that have a negative impact on work efficiency. To improve ventilation efficiency and eliminate coal dust, this article presents a CFD-DPM numerical modeling method that integrates a DEM collision model based on the finite element method to analyze the motion characteristics of airflow and dust particles in the mine tunnel, while considering collisions between particles and between particles and walls. The article analyzes the distribution of wind speed, the dispersion of dust in the space around the roadway, and dust concentrations at distances of 1 m, 3 m, and 6 m from the working personnel and at a position 1.5 m above the roadway floor, corresponding to the breathing zone of the workers, with varying parameters such as velocity and duct position. The results indicate that with a wind velocity of V = 18 m/s and an air duct height h = 3.0 m, the best dust reduction results are achieved, and they provide theoretical guidance for selecting and optimizing ventilation parameters in dust control.

Research on Resistance Characteristics of Fire Zone of Mine Tunnel Fire and Construction of Calculation Model

To investigate resistance change in the fire area of a roadway caused by roadway fires, a mathematical calculation model for thermal resistance is developed. Theoretical research is conducted to analyze the factors influencing resistance change through theoretical derivation, revealing that temperature is a key factor contributing to the change in thermal resistance. By leveraging the correlation between changes in CO concentration and temperature on the downwind side of the roadway within the fire zone, researchers developed mathematical models to predict temperature increases at various points downwind of the fire source. These models were then used to determine the mathematical relationship governing the change in thermal resistance. The accuracy of the numerical simulation software was validated using Fluent numerical simulation software and scaled-down model experiments. Full-scale numerical simulation experiments were conducted to investigate the fire characteristics of roadway fires and validate the thermal resistance mathematical model. The results indicate that the thermal resistance in the numerical simulation is 7.55 Pa at 20m from the fire source and 5.54 Pa at the end of the roadway. The decrease in resistance is linear. The minimum error between the thermal resistance calculated by the mathematical model and the gradient of the pressure drop in the numerical simulation is 0.03 Pa, approximately 2.3%. Furthermore, the fitting degree of the pressure drop in each section is as high as 97.7%. The calculation model demonstrates high accuracy and offers a theoretical foundation for investigating fire resistance in tunnel fire.

A novel concrete-filled flange steel tubular composite supports for tunnels: A numerical perspective

In this study, a new type of concrete-filled flange steel tubular composite support (referred to as a concrete-filled flange steel composite support) was designed to address the inadequate bending load-bearing performance of concrete-filled steel tubular supports. The bending load-bearing performance of concrete-filled flange steel tubular beams was studied through numerical simulations, revealing the improvement effect of welded T-section steel on the bending performance of the beams. The load-bearing characteristics of the concrete-filled flange steel composite and tubular supports were explored through theoretical analysis. Using a coal mine tunnel, the effectiveness of the concrete-filled flange steel composite support for controlling tunnel deformation was verified. The results indicated that the improvement in the bending load-bearing performance of concrete-filled flange steel tubular beams was mainly due to the bending load-bearing capacity of the T-section steel. Increasing the height of the T-section steel web effectively enhanced the bending load-bearing performance of the concrete-filled flange steel composite support when the same amount of steel was used, and the load-bearing performance of the concrete-filled flange steel composite support was significantly better than that of the traditional concrete-filled steel tubular support. With a lateral pressure coefficient farther from 1, the superiority was more pronounced.

Modeling Heat Transfer for Assessing the Convection Length in Ventilated Caves

AbstractThe present study focuses on heat transfer in ventilated caves for which the airflow is driven by the temperature contrast between the cave and the external atmosphere. We use a numerical model that couples the convective heat transfer due to the airflow in a single karst conduit with the conductive heat transfer in the rock mass. Assuming dry air and a simplified geometry, we investigate the propagation of thermal perturbations inside the karst massif. We perform a parametric study to identify general trends regarding the effect of the air flowrate and conduit size on the amplitude and spatial extent of thermal perturbations. Numerical results support the partition of a cave into three regions: (a) a short (few meters) diffusive region, where heat mainly propagates from the external atmosphere by conduction in the rock mass; (b) a convective region where heat is mainly transported by the air flow; (c) a deep karst region characterized by quasi‐constant temperatures throughout the year. Numerical simulations show that the length of the convective region is approximately proportional to the amplitude of the flowrate annual fluctuations divided by the square root of the cave radius. This result is tested against field data from a mine tunnel and two caves. Our study provides first estimates to identify climate sensitive regions for speleothem science and/or ecosystemic studies.

Research Status of Friction Interface Evolution Mechanism of Non-magnetic Steel

The non-magnetic drill pipe (composed of male and female thread joints and rod bodies) is the key component of the directional drilling technology equipment for gas extraction in coal mine tunnels. The thread joint and the drill pipe body are connected by continuous drive friction welding. In the study, it was found that the banded structure appeared in the joint of continuous drive friction welding of non-magnetic steel, which reduced the strength of drill pipe. At the same time, it is found that the heat flow mode is one of the key factors affecting the banded structure, and the heat flow mode is based on the evolution of the interface plastic ring. In this paper, through the review of the research status of the interface evolution law of non-magnetic steel continuous drive friction welding, the experimental method for the study of the interface evolution law of non-magnetic steel continuous drive friction welding is found.

Numerical investigation study on tensile-shear failure behavior of rock bolts in inclined strata mining tunnels

In response to the problem of severe deformation and failure of the surrounding rock of the mining tunnels in inclined strata, a tensile-shear failure numerical model of rock bolts was adopted to analyze the rock bolts failure behavior and the surrounding rock mechanical response, and explore the influence of different factors on rock bolts failure. The results indicate that: (1) As angle between the rock bolt and the interface decreases, the shear force of increases, and the rock bolt is easier to fracture. The maximum displacement is 250.2 mm of fractured position. A new evaluation index of shear axis ratio was proposed. The larger the shear axis ratio, the rock bolt is easier to fracture. The shear axis ratio at the interface has increased by 95 % compared to the non interface. (2) The plastic zone and the surrounding rock deformation exhibit the same inclination trend as the strata. In final state, the maximum deformation is 297.7 mm at the bottom and top position perpendicular to the rock bolts at the interface. At the moment of rock bolts fracture, the interface displacement of surrounding rock immediately increased by about 10 mm. And the stress in the surrounding rock decreased about 1 MPa. The weakening effect of surrounding rock stress shifts with the change of rock bolt fracture position. The stress at the arch waist decreases by 44 %, the stress at the arch crown decreases by 25 %. When the fracture of the rock bolts at the arch crown and arch waist ends, the stress at the side wall begin to decrease by 40 %. (3) As the inclination angle increases, the deformation of the surrounding rock and the number of rock bolt failures increase. The range of the plastic zone in the surrounding rock gradually increases, and the degree of rock bolts asymmetric fracture more aggravated. As the diameter of the rock bolt increases, the fractured number of the rock bolts and range of plastic zone decreases.

Numerical analysis of stress and deformation characteristics of compressed air energy storage chambers developed from a modified coal mine tunnel

The use of abandoned coal mine tunnels as underground compressed air energy storage (CAES) facilities has garnered significant attention given that it effectively repurposes unused underground space and enhances the efficiency of renewable energy utilization. However, existing coal mine tunnels, without optimization and retrofitting, may not meet the stability requirements of compressed air energy storage repositories. Sectional transformation is a retrofitting method with excellent optimization effects. In this study, numerical simulation based on Midas software was employed to create a three-dimensional model of straight-wall arched mine tunnels. The stress and displacement deformation of the tunnel sections were simulated under internal pressure of 10 MPa, and scenarios with no modification and circular-section backfilling were compared. The outcomes of the study are (1) For deeply buried soft rock mines, the existing structure without modification may not meet the stability requirements of compressed air storage facility due to low rock strength. (2) In the unmodified scenario, stress concentration effects and excessive floor tensile stress occur near the tunnel closure. (3) Backfilling straight-wall arched tunnels into circular shapes effectively reduces stress and displacement along the tunnel walls, preventing stress concentration near the tunnel closure. This study provides a retrofitting approach for repurposing abandoned mines into compressed air energy storage facilities, providing guidance for future projects facing complex geological conditions.

Numerical Simulation Study of the Optimal Parameters for Dust Reduction by an External Air Curtain (EAC) in Continuous Mining Tunnel

Numerical Simulation Study of the Optimal Parameters for Dust Reduction by an External Air Curtain (EAC) in Continuous Mining Tunnel