Seam Area Research Articles

Research on identification method of coal-rock interface based on ground penetrating radar in the driving face of soft coal seam

Coal–rock interface recognition is one of the key challenges in advancing unmanned rapid tunneling systems. To address this, a method based on variations in ground-penetrating radar (GPR) reflection wave amplitude is proposed for identifying coal-rock interfaces in soft coal seams. A mathematical model derived from Maxwell's equations calculates the coal seam area based on the reflected wave amplitude. Experiments using a 400 MHz radar antenna show that the method achieves identification errors of 3.58 cm, 3.74 cm, and 4.23 cm for coal-to-rock ratios of 1:2, 1:1, and 2:1, respectively. In practical applications within a coal mine excavation face, the identification error is 6.64 cm. This method provides crucial data for drum height adjustment and cutting arm speed regulation in unmanned tunneling systems.

Experimental study on fatigue damage mitigation in welded beam-to-column connections with passive vibration control

To investigate the effectiveness of a viscous fluid damper (VFD) in mitigating fatigue damage in welded beam-to-column connections, six specimens were manufactured with the full penetration groove weld process. These specimens were divided into three groups: S1, S2, and S3, each containing two specimens. One specimen in each group was equipped with VFD, while the other was not. All specimens underwent the same elastic cyclic loading stage, but a different plastic cyclic loading stage for each group. The study results indicate that the presence of VFD can significantly enhance the load-bearing capacity of the welded beam-to-column connection by 10%–15% when subjected to the same displacement amplitude at the beam end. The primary cause of failure in the welded beam-to-column connection is the fatigue damage of the weld toe on the beam flange, which requires more attention during the welding process. Additionally, the VFD can effectively reduce stress concentration at the weld seam area, leading to a maximum of 50% decrease in the maximum stress near the weld toe of the beam flange center, as observed in our study.

Research and Application of High Efficiency Pressure Relief Technology for Ultra-high Pressure Hydraulic Slotted Coal Seam

In order to solve the technical problem of efficient pressure relief of the impact coal seam, the principle of ultra-high pressure hydraulic slit relief and anti-impact technology is expounded, and the ultra-high pressure hydraulic slit device with working pressure up to 100MPa is selected as the pressure relief equipment of coal seam. The field test of high-efficiency pressure relief by ultra-high pressure hydraulic slotting in impact coal seam was carried out. The test showed that the slotting radius of No.3 coal in Tangkou Mine could reach 1.5m under the condition of 100MPa slotting pressure. The stress variation in seam area and large diameter drilling area is compared and analyzed. The stress in seam area decreases significantly by 40%. The stress of bolt (cable) and the deformation of surrounding rock in the slit area are investigated. Compared with the large-diameter pressure relief area, the increase value of bolt is lower and the increase value of cable is significant in the hydraulic slit test area. The technical benefits of hydraulic slotting and large-diameter drilling are summarized and compared. The engineering quantity of drilling with ultra-high pressure hydraulic slotting is reduced by 60%, and the coal output is 2.5 times of that of large-diameter drilling. The large-diameter drilling provides limited pressure relief space for coal seam, but the ultra-high pressure hydraulic slotting technology can effectively increase the deformation space in the coal body and reduce the elastic energy stored in the coal pillar, so as to achieve a good pressure relief effect. The field test shows that compared with large diameter drilling, ultra-high pressure hydraulic slotting technology has remarkable effects of pressure relief, shock absorption and shock prevention.

Study on pulse current auxiliary heating process of submerged arc welding

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

GNSS/UWB/INS indoor and outdoor seamless positioning algorithm based on federal filtering

An integrated navigation system plays an important role in the application of indoor and outdoor seamless positioning. Essentially, it is a flexible fusion positioning of multiple sensors with different combinations. The Global Navigation Satellite System (GNSS) can provide high-precision positioning and navigation in an outdoor environment with good observation conditions. Ultra-wide Band (UWB) has the characteristics of great bandwidth and anti-multipath, which can be applied to provide high-precision positioning and navigation indoors. Inertial Navigation System (INS) has independent navigation capabilities that can be tightly combined with GNSS and UWB to enhance positioning robustness. In response to the problem of a single sensor struggling to provide reliable location information for indoor and outdoor seamless positioning, this study applies federal filtering to integrate and construct the GNSS/UWB/INS integrated positioning algorithm based on Horizontal Dilation of Precision (HDOP) of UWB and carrier-to-noise ratio of GNSS weighting. The gross errors are first detected during the data preprocess, and an adaptive weighting approach to reduce the influence of the anomalous observations is constructed. The tight combination of GNSS/INS and UWB/INS is implemented in the subfilter of the federal filtering. In the main filter, the weights of the two subfilters are adjusted based on HDOP and carrier-to-noise ratio weighting, and the information is allocated and fused to reduce the impact of potential poor UWB geometric configuration on the positioning solutions. It is proven that the error in the horizontal direction in the indoor and outdoor seam area is less than 10 cm. Compared with conventional federal filtering and Huber-based Kalman filtering, the algorithm in this study improves the accuracy of the reference point in indoor and outdoor seam area by 46.1% and 15.4%, respectively, which is beneficial for applications in indoor and outdoor seamless activities.

Ensuring the confection strength of adhesives based on SBS copolymers of various topologies

This work is devoted to the improvement of a new building material for the road market - connecting bitumen-polymer tapes. The conditions for the use of such tapes have recently been significantly expanded both as a result of the harsh operating temperature conditions of the coating, and due to the need for road construction work at unsatisfactory temperature and humidity. The study attempts to assess the feasibility of using some brands of styrene-butadiene thermoplastic elastomers as a polymer base of adhesives to provide short-term increased strength of fastening of connecting bitumen-polymer tapes to the side surfaces of the crushed stone base for the period before laying a hot asphalt concrete mixture and forming a monolithic asphalt concrete coating in the seam area. The work on the study of a new type of material was hampered by the lack of appropriate technical standards for checking the quality of bitumen-polymer tapes for delamination and separation. Therefore, a high-hardness rubber compound based on styrene-butadiene rubber was chosen as a model solution. The data obtained confirmed the assumption about the effectiveness of various brands of SBS polymers to ensure the confectionery resistance of the base. The established dependencies were distributed and confirmed for highly porous concrete and embedded parts of metal fences.

Influence of Friction Stir Weld Parameters on the Corrosion Susceptibility of EN AW‐7075 Weld Seam and Heat‐Affected Zone

Friction stir welding enables joining of high‐strength, lightweight aluminum alloys, e.g., EN‐AW‐7075, below the melting point by induced plastic deformation. Therefore, heat transfer into the adjacent regions beneath the weld seam is significantly reduced as compared to fusion welding processes such as laser beam welding. However, specific zones along the weld seam area are susceptible to localized corrosion due to grain growth and the precipitation of intermetallic phases. Thus, several approaches toward lowering the corrosion susceptibility of the heat‐affected zone are presented. Special interest is given to increasing the plastic deformation by the use of novel multipin welding tools that eventually facilitate reduced heat input during welding as a result of substantially lower tool revolutions. The corrosion behavior is tested by means of full material immersion tests and electrochemical measurements which provide insight into the corrosion kinetics. Using pre‐ and postmortem microstructural analysis, the mechanisms influencing the initiation of corrosion can be identified. Supported by in‐operando temperature measurements, the varied welding parameters and their interrelationships to corrosion resistance can be derived. Furthermore, recommendations on optimal welding parameters to obtain enhanced corrosion resistance can be deduced.

Seismic performance of a new precast concrete frame joint with a built-in disc spring

A new, precast concrete frame beam-column connection is designed in this research. The connection adopts the assembly mode of the precast column and seam area jointly to maintain the integrity of the joint area and increase the assembly efficiency. Based on the conventional grouting sleeve connection, a disc spring device is constructed on the beam end to improve the ductility of the joint. Ten connecting specimens were tested under low cyclic loads, including two monolithic connections, four ordinary precast connections, and four new precast connections. The test parameters included the joint type and axial pressure ratio, and the difference in the seismic performance was determined by evaluating the failure mode, hysteresis characteristics, stiffness degradation, energy dissipation, and shear deformation of the joint area. Compared to monolithic connections, conventional precast connections display similar hysteresis characteristics. Although their ductility is slightly lower, their bearing capacity is higher. Compared with the previous two connections, the new connection with the built-in disc spring device has superior seismic performance. The axial pressure ratio is a significant aspect in determining the failure mode of the precast connection, and the specimen exhibits less shear damage at a larger axial pressure ratio.

An experimental and numerical investigation of energy absorption of sportswear in seam area

This study aims to investigate the energy absorption of seam areas in sportswear. Weft knitted fabrics with two structures of plain and rib were fabricated by polyester/Lycra and viscose/ Lycra yarns. Fabrics were stitched in two stitch classes. Moreover, two types of seams were considered. A pull-out test was carried out on all samples to determine the energy absorption values. Furthermore, a finite element model was applied to predict the energy absorption of each structure. The unit cell of each sample was created in ABAQUS software and the tensile load was applied to the stitch yarn. The unit cells of the fabric and the stitched section were modeled in the meso-scale and then elastic and viscoelastic properties of the yarns were assigned to the model. The energy absorption of the sample with rib pattern, lapped seam, and 607 stitch class was more than other samples. Also, the numerical and experimental results showed a high correlation with each other in samples with 304 stitch class and flat seam type.

Research on a high-precision extraction algorithm for aircraft skin seam features

The precision measurement of the surfaces of aircraft based on structured light technology is an important development direction of aircraft skin assembly and maintenance. Based on the characteristics of the point cloud in the skin seam area, the height difference mutation method and the slope value maximization method are proposed to extract the edge points of the feature point cloud, achieving the high-precision extraction of the flush and gap of the aircraft skin. First, the 3D point cloud data of the feature region are generated with fringe projection profilometry, and an adaptive matching calibration algorithm is used to calibrate the feature region with high precision. A 3D feature data calculation model is established for both straight line and curve seams, and the edge points of the feature point cloud are extracted with the height difference mutation method and the slope value maximization method to achieve the high-precision extraction of 3D feature data of aircraft skin seams. In this study, an aircraft seam 3D data measurement model is systematically established. This model is suitable for both straight lines and curves. Compared with the algorithm for the feature seam extraction of the slope difference skin, the model has better robustness, and the average measurement error is reduced to approximately one-third of that of the classical algorithm.

The design, simulation, and adjustment of the Vietnam men’s Ao dai on the CLO3D software

The study presents the results of the design, simulation, and adjustment of middle-aged men’s Ao Dai from 30 to 60 years old in Ho Chi Minh City. This research combines two methods of 2D design on the Gerber software and 3D design on the CLO3D software, of which the main simulated patterns’ material is cotton sateen fabric. An avatar is used to simulate men’s Ao Dai which has the average measurements of the 378 measurement samples. There are three steps to simulate and edit. At first, the patterns are draped on the avatar. The sample does not achieve a smooth, flat fit in the side seam and waist area when they drape on the avatar. After patterns are adjusted at the side seam, finally, these patterns are draped again to meet the standard of smooth and flat appearance on the simulated model’s front, back, and side faces. The study was conducted on one model that has suitable dimensions for Vietnamese men, so there will be additional avatar data in the CLO3D software database. This is very useful for fashion and technique designers in garment businesses.

Effect of subgrade on leakage through a defective geomembrane seam below saturated tailings

Experiments are conducted to quantify leakage through saturated tailings (with 30% fines) underlain by a geomembrane with either a 100-mm-length knife cut slit defect or a 110-mm-length defective extrusion seam. Various subgrades, a poorly graded gravel (GP) with or without nonwoven geotextile (450 or 1420 g/m2) above, a well-graded gravel (GW), and a poorly graded sand (SP) are evaluated. Test results show that leakage through the slit defect and defective seam increase with the subgrade coarseness and subgrade unevenness. The inferred upper and lower bounds opening width of a slit based on the measured leakage increase with the overburden pressure and are categorized for each subgrade. Indentations in the overlapped defective extrusion seam area arise from both the entrapped materials inside the overlap and the materials underlying/overlying the geomembrane, incrementally inducing a greater interface transmissivity with the increasing stress. Overlain by tailings at total overburden pressure of 510 kPa and water head of 35m, leakage through the slit defect is 1.1L/day for SP, 2.2L/day for GW, 2.6–3.3L/day for both GP and uneven GW; leakage drops to 0.8L/day with a geotextile layer directly above the GP; leakage through the defective extrusion seam is 0.4L/day for SP and 0.8L/day for GW.

Traumel C In Optimizing Wound Healing in The Area of The Incision of The Uterus After a Planned Cesarean Section

The aim of the study was to determine the possibility and feasibility of using Traumel With no antibiotic prophylaxis to improve wound healing processes on the uterus after cesarean section. 46 maternity hospitals were examined. In 26 patients, Traumel was used in the postoperative period, and in 20 only antibiotic prophylaxis was used. The postoperative period in all women proceeded without complications. But the indices of the involution of the seam area (IIPSH) and neutrophil-lymphocytic index (NLI) indicated more optimal wound healing on the uterus in women who used only Traumel C.

Experimental tenorrhaphy with the use of microsurgical tendon holder

Objective . Damage to the tendons of the extremities is one of the most frequent injuries of the human musculoskeletal system. Tenorrhaphy, aimed at restoring their integrity, is a technically complex surgical intervention, including access with the release of the ends of the tendons, their retention and repeated interception during suturing with a thread. During surgery, the tendon inevitably undergoes additional trauma from compression by surgical instruments. As a result, there is a violation of the ultrastructure, blood supply and weakening of the ends of the sutured tendon. In turn, this prevents accurate adaptation and causes deformation in the seam area, promotes thread eruption. At the same time, tendon regeneration proceeds with a pronounced scar-adhesive process, sliding properties are violated, tenogenic contractures are formed. Purpose of the study. To evaluate the effect of the tendon capture and retention method during tenorrhaphy on the microanatomic structure of the tendon. Material and methods. A new instrument for performing tenorrhaphy is proposed. 12 experimental tenorrhaphies were performed on the tendons of the limbs of people amputated for medical reasons, using tweezers and an original tendon holder, followed by histotopographic examination of stitched tendon samples. Results and discussion . In the course of the study, it was found that the method of capturing and holding the tendon during tenoraphy has a significant impact on its anatomical structure. When holding tendons with tweezers, violations of the tendon structure and damage to its membranes were observed. The tendons held during the operation with the help of a tendon holder were distinguished by the preservation of the macromicroanatomic structure of the tendon itself and the surrounding tissues. Conclusion . The use of a microsurgical tendon holder makes it possible to ensure the safety of the macromicroscopic structure of the tendon, the anatomicity and precision of the tenoraphy, in comparison with traditional methods of tendon retention.

Research on a Spontaneous Combustion Prevention System in Deep Mine: A Case Study of Dongtan Coal Mine

ABSTRACT Due to the influence of high ground stress, high ground temperature, high water inflow and other problems in deep mines, coal spontaneous combustion (CSC) is seriously harmful. This paper studied the variation law of three kinds of indicator gases in the process of coal heating in deep mines, and established a multi-parameter gas indicator prediction system for CSC. Secondly, in view of the shortcomings of the negative pressure bundle tube. A positive pressure beam tube monitoring system for early warning of CSC was developed, the accuracy of sampling data was verified on site, and the high temperature area in the well was further identified by isotope radon measurement. Combined with the positive pressure beam tube monitoring system, to realize the joint detection of uphole and downhole. Finally, according to the detection results of the fire area, the fire prevention methods for small space fire area, multi-coal seam and multi-source air leakage complex fire area and large-area concealed fire area are determined. The above-mentioned CSC early warning and prevention system was applied in Dongtan (DT) Coal Mine, and a good fire prevention effect was achieved. In this paper, the CSC prevention and extinguishing system established has important significance in the prevention and control of mine fires.

Seepage Law of Nearly Flat Coal Seam Based on Three-Dimensional Structure of Borehole and the Deep Soft Rock Roadway Intersection

Exploring the evolution characteristics of gas seepage between boreholes during the drainage process is critical for the borehole’s layout and high-efficiency gas drainage. Based on the dual-porous medium assumption and considering the effect of stress redistribution on coal seam gas seepage characteristics, a coal seam gas seepage model with a three-dimensional roadway and borehole crossing structure has been established and numerically calculated, concluding that the coal seam is between the drainage boreholes. The temporal and spatial evolution characteristics of gas pressure and permeability help elucidate the gas seepage law of the nearly flat coal seam associated with the deep soft rock roadway and borehole intersection model. The results indicate that: (1) The roadway excavation results in localized stress in some areas of the surrounding rock, reducing the strength of the coal body, increasing the expansion stress, and increasing the adsorption of gas by the coal body. (2) Along the direction of the coal seam, the permeability decreases initially and then increases. The gas pressure in the coal seam area in the middle of the borehole is higher than the pressure in the coal seam around the borehole, and the expansion stress and deformation increase, reducing the permeability of the coal body; when near the next borehole, the greater the negative pressure, the faster the desorption of the gas attracts the matrix shrinkage effect and causes the coal seam permeability rate to keep increasing. (3) The improvement of gas drainage with the overlapping arrangement of two boreholes firstly increases and then decreases as time goes on. (4) When the field test results and numerical simulation of the effective area of gas extraction are compared, the effectiveness of the model is verified. Taking the change of the porosity and the permeability into the model, it is able to calculate the radius of gas drainage more accurately.

PERFORMANCE CHARACTERISTICS OF NICKEL-CONTAINING STEEL STRUCTURES DURING MECHANIZED WELDING-SURFACING WITH MODIFIED (DOSED) ELECTRODE WIRE FEEDING

Purpose. To study and analyze in a comparative order the influence of factors of the controlled pulse process of electrode wire supply on some basic mechanical characteristics of seams and welded rollers in the processes of welding and surfacing of nickel-containing steels.
 Methods of research. The study the mechanical characteristics of seams and welded rollers was carried out using modern laboratory equipment and appropriate techniques. This made it possible to determine how the pulse feed parameters affect the strength characteristics of the weld and near the weld zone over the entire cross-sectional area of the weld or weld layer. Detailed characteristics of feed pulses were determined using a welding process analyzer to obtain oscillograms of power parameters of arc combustion with their analysis, including determining the stability of the arc process for different types of pulses. Important for the improvement of welding results is the controlled nature of the electrode metal transfer synchronous with the pulsed movement of the electrode. It is noted that the energy consumption of the arc process during the pulse supply of the electrode wire with an indication of its reduction compared to traditional welding.
 Experimental work was performed using a special electrode wire, which is usually used for welding and surfacing of nickel-containing steels. These processes were carried out in a protective environment of CO2 in automatic mode.
 Results. Due to the fact that the strength characteristics of the weld are among the most important, attention is paid to their definition and analysis. The strength characteristics depend on many parameters, in particular the thermal characteristics of the process, the structure of the weld metal, the presence of non-metallic inclusions and so on. All these factors were studied with the help of appropriate instruments, and on the basis of numerous comparative photos of microstructures on sections of the cross section. The analysis of the sections revealed the types of microstructures obtained, the presence of inclusions and more. It is determined, in particular, that the structure of weld metal in pulsed electrode wire welding differs significantly from the structure of traditional welding in reducing inclusions, finer grains, etc., which improves the mechanical properties of the weld and seam area.
 Scientific novelty. Based on a series of experimental studies, the use of pulse algorithms for the movement of the electrode wire with certain parameters in automatic mode for welding and surfacing of nickel-containing steels to improve the mechanical properties of seams and welded rollers.
 Practical value. It is determined that the method of pulse welding of electrode wire to the controlled variant, including nickel-containing steels is effective and can be widely used in industry using specially designed equipment that provides a suitable process with stronger characteristics.

Cocompetitive Characteristics and Quantitative Design of Engineering Parameters for Coal Gas Predrainage Boreholes

Quantitative design of the optimal gas extraction engineering parameters has always been a key scientific problem to meet the predrainage target of the coal seam, which is paid great attention to and urgently expected to solve for the gas extraction engineering of coal mine. In this paper, the governing equation of the evolution of coal seam gas content is established under the interference and cooperation of gas extraction by boreholes, and the calculation formula of gas cooperative efficiency is defined. Based on gas-air mixed flow, a multifield coupling 3d model of coal gas extraction using boreholes was developed. The content, method, and principle of optimal spacing parameter design of extraction borehole were proposed, and the constraint conditions and objective function of optimal design were constructed. The flow characteristics of gas extraction using boreholes in the coal seam area and the influence of different parameters on gas extraction effect are studied. The cooperative and competitive behaviors of gas extraction by boreholes in coal seam are revealed. The results show that borehole spacing, seam fracture permeability, and gas adsorption constant have significant effects on the synergistic and competitive effects of gas extraction, while the negative pressure of gas extraction and coal matrix permeability have little effects, but the negative pressure of gas extraction has great effects on gas extraction concentration. Finally, Comsol With Matlab is used to solve the multiconstraint nonlinear optimization problem of gas drainage engineering parameters along coal seam in 18401 working face of Tunlan Coal Mine. The effect of actual gas extraction investigation is very remarkable, which provides a quantitative calculation basis for scientific gas extraction in coal mine.

Studies Regarding FCAW Welding of Dissimilar Joints between Duplex Stainless Steel and Naval Carbon Steel

In this paperwork is presented a study of dissimilar welding with FCAW welding process, between duplex stainless steel S31803 (1.4462) and naval carbon steel EH36 (1.0546), being analyzed all the considerations related to their weldability, resulted mechanical properties, microstructure and evaluation of the toughness and hardness of the weld seam and HAZ area.

Numerical Simulation Research on the Pressure Relief and Permeability Enhancement Mechanism of Large-Diameter Borehole in Coal Seam

In order to achieve high-efficiency extraction of coal seams with large-diameter borehole and large flow rates, and to rapidly reduce coal seam gas content and pressure, a large-diameter borehole coal seam pressure relief and permeability enhancement technology is proposed. In this paper, numerical simulation is used to study the mechanism of pressure relief and permeability enhancement in coal seams with large-diameter boreholes, and the evolution of stress, cracks, gas, and permeability of coal bodies around boreholes with different diameters is discussed. The research results show that the stress changes in the coal body around the borehole are symmetrically distributed around the borehole. The stress evolution controls the evolution of the coal body’s cracks. Firstly, damage occurs around the borehole and then extends to the upper left and right corners, like a butterfly spreading its wings. The crushing zone increases with the increase of the hole diameter, and the impact radius of the 100-mm, 200-mm, 300-mm, and 350-mm diameter borehole rupture is 0.375 m, 0.65 m, 1.0 m, and 1.25 m, respectively. The rupture radius of the double 350-mm diameter borehole can reach 2.4 m. The larger the diameter of the borehole, the more fissures will be produced, and the air permeability of the coal body in the affected coal seam area will obviously increase. The research results provide theoretical support for gas drainage in soft, low-permeability, high-gas coal seams.