Metal Arch Research Articles

Determination of the type of arched carbon fiber reinforced fastening of the preparatory opening for the conditions of the «Dniprovska» mine in weakly metamorphized rocks

The object of study is an arched carbon fiber-reinforced support of constant cross-section in a layered massif of weakly metamorphosed rocks. The article presents an analysis of the possible use of arched fiber-reinforced support of constant cross-section in a layered massif of weakly metamorphosed rocks for the conditions of the «Dniprovska» mine (Ukraine) around the preparatory opening. An analysis of the stability of mine openings in Western Donbas mines has shown that it is necessary to modernize the support system by introducing carbon fiber. The main reason for the low stability of the opening is the insufficient load-bearing capacity of the support, while its technical characteristics do not take into account the complex mining and geological conditions. The increase in stresses at mining depth is associated with impact safety, which is a serious problem during mining. Metal arch supports are deformable and have high rock loads and require a high level of energy absorption, i. e., to be very strong and flexible to withstand significant loads and avoid large displacements of the opening walls. Carbon fiber-reinforced plastic is able to ensure the stability of the fastening system and eliminate the existing disadvantages of typical metal arch fasteners, namely, high labour intensity, low production speed and high weight of the structure. In this article, the stress-strain state for the specified conditions and the carbon fiber-reinforced plastic arch support of constant cross-section was analyzed using the SolidWorks software product, taking into account the physical and mechanical properties of carbon fiber-reinforced plastic and layered rocks. Taking into account the results of laboratory tests of an equivalent layered array on a press made of PLA and carbon fiber, the dependence of deformations of the equivalent array with increasing load was established. The use of arched carbon fiber supports of various cross-sections can ensure the opening stability by reducing the intensity of stresses around its contour. On the basis of this study, a rational arched composite support of constant cross-section was proposed for the conditions of the «Dniprovska» mine. The obtained results indicate the need for further research, which will be considered in the author's future works.

SINGULARITIES OBSERVED IN THE CALCULATION OF THE MODAL DAMPING RATIO OF A LONG‐SPAN METAL ARCH BRIDGE

AbstractWithin the recent studies that are being carried out in the structural health monitoring of bridges, it has been observed that the results of the modal damping ratio can be influenced by some ambient variables and significantly depend on the calculation method that is adopted. In this paper, the main conclusions obtained in the study of the dynamic behaviour of a real structure, the viaduct “Arcos de Alconétar”, in Spain, whose main span is a long metal arch, is reviewed. With this aim, the results obtained from the instrumentation installed during the initial months after its traffic opening are analysed.

Development of a system for ranking geomechanical factors, which influence the stability of uranium mines workings

The subject of research presented in the article are processes that take into account the influence of geomechanical factors on the stability of mining workings of uranium mines. The purpose of this work is development of a system for ranking geomechanical factors by the degree of danger based on the analysis of risk factors that affect the stability of uranium mines. The work uses critical analysis and generalization of both own research results and the results of domestic and foreign authors. The geomechanical factors that affect the stability of the mining workings of uranium mines have been determined. It is shown that their influence has both a direct and an indirect effects due to the connection with mining-geological and technological parameters. The stability of the workings is significantly influenced by mining and technical factors (outcropping time, working space length, floor height, compression properties and structure of the backfill mass, chamber width, dynamics of cleaning works progress), mining and geological factors (depth of mining, thickness of the ore body, strength (deformation)) and physical and mechanical properties of the rock mass. In addition, the engineering and technical conditions of mine construction have a significant impact, in particular, the form and size of the workings, their orientation in the massif, the method of carrying out and supporting, the design and technology of fastening, etc. It is practically impossible to simultaneously take into account all factors in an analytical way, so it is necessary to select one or two main factors that are of decisive importance for the description of a specific geomechanical process. The originality of the work is the proposed ranking of geomechanical factors that affect the stability of mining workings of uranium mines. The ranking of geological, physical and mechanical factors on the stability of the chamber system elements at underground mining of uranium ores, according to the degree of attenuation of the influence, is as follows: strength of rocks → structure of the massif → angle of fall of the deposit → water content of the deposit → thickness of a seam. The ranking of the influence of support preparatory and capital workings on their stability, according to the degree of risk decrease, is as follows: no support → grid with anchors → sprayed concrete → wooden support → metal frame support with tightening → metal arches in concrete. Generalized ranking of the influence of the most significant factors on the stability of mining workings: geological, physical and mechanical factors → parameters of the development system → fastening technologies.

Numerical modelling of enhancement of the capacity of buried metal culverts by using geogrids

This paper presents a two-dimensional numerical modelling analysis of a flexible buried corrugated metal arch culvert in Enkoping, Sweden. The numerical results of this study are validated against field measurements of the culvert crown deformation, thrust, and bending moments recorded during backfilling. To model the backfill soil, the hardening soil with small strains (HSs) material model is used because of its efficiency in simulating the soil-structure interaction. Furthermore, in a numerical investigation of the stress distribution at the culvert invert, it is found that weakness of the foundation soil has an insignificant impact, due to stress dissipation resulting from arching actions. The numerical modelling analysis also investigates the use of geogrid layers with dead end bolts in the soil cover above the culvert crown during the application of static surface loads, as an innovative technique to improve the load capacity of the soil-culvert system. The results show a reduction in culvert crown deformation and internal forces when geogrid layers are used. This indicates the efficiency of geogrid layers in improving the load capacity of existing buried culverts or overcoming deficiencies in culvert serviceability by reducing the impact of applied loads.

The effect of pre-heating distance of shielded metal arc welding on the mechanical properties of AISI 1045 steel

Welding is a method of joining metals by utilizing local heat to form a metallurgical bond between the metals. The most common welding is electric welding, including the Shielded Metal Arch Welding (SMAW). This type of welding uses a filler wire or electrode. To reduce weld cracks and cooling rates in the weld metal and heat affected zone (HAZ) area, it is necessary to carry out a pre-heating process. Pre-heating is the application of heat to the material to be welded using oxyacetylene welding or a gas torch. This study aims to determine the appropriate pre-heating distance for the welding process of AISI 1045 steel, classified as a type of medium carbon steel widely used in shafts, gears, and piston connecting rods in motor vehicles. The parameters used in this study were the pre-heating distances of 1.5cm, 3cm, and 4.5cm that were preheated at a temperature of 150°C, using LB-52U type electrodes with a diameter of 2mm.

Mechanical performance of a 3D printed scaled mine roadway model

This study exploits 3D concrete printing technology to build a physical model of a mine roadway, 30 times scaled down of its engineering prototype. The supporting arches were also scaled accordingly and then manufactured by 3D metal printing. By assembling the 3D printed concrete model and metal arches, the engineering scenario was reproduced in laboratory for a monotonic increasing loading. Loading was assisted by multiple measurement techniques, namely: digital image correlation (DIC), acoustic emission (AE), strain gauges . Attention was dedicated to the damage initiation and evolution of the 3D printed components. The results highlighted the advantages of the 3D printed model to understand the collapse mechanism of the layered concrete, which involved the collapse nearby the excavation and the failure of the arches. Moreover, the hypotheses and limitations of this study were discussed with advices for future researches. Finally, engineering data from the simulated site were analyzed, and it found that the 3D printed model predicted the actual deformation characteristics of engineering prototype with reasonable accuracy.

Additive manufacturing technology in mining engineering research

AbstractNowadays, additive manufacturing, or 3D printing (3DP), though not a new technology in many industrial fields, is still relatively novel in mining engineering. This study explored the application of 3D metal printing, 3D polylactic acid/acrylonitrile butadiene styrene printing, and 3D concrete printing in coal mining. Some examples of physical models established via 3DP technologies were studied in detail, namely, 3DP bolts, 3DP steel ladder beams, 3DP face plates, and 3DP metal arches, which were installed in scaled 3DP concrete prototype models of coal mine excavation. Through the comprehensive laboratory loading tests, the models could simulate the damage scenario highly similar to the real failures. The results show that the 3D printed physical models greatly improved the accuracy and reliability of experiments. On this basis, the conceptual design of a 3DP machine for physical models was proposed, which had the potential of resembling the strata deformation/collapse in natural scenarios. Through assessing the applicability of the additive manufacturing technology in mining engineering, this study aimed to further explore its potential applicability in other engineering contexts such as slope controlling, large underground engineering, and underground space stability.

NUMERICAL EVALUATION OF SPECIFIC ABSORPTION RATE IN HUMAN HEAD AND TORSO FOR WEARABLE WIRELESS DEVICES IN UNDERGROUND MINE SCENARIOS.

The radiofrequency field levels may increase in confined environments, such as underground mines, due to reflections from inner boundaries (walls and arches). This study investigated the specific absorption rate (SAR) in the head and torso of a miner wearing a wireless device in underground mine scenarios. Two high-resolution voxel models were used to analyse the effects of a tunnel structure, a metal arch and a safety helmet at 2.4GHz and 868MHz. The results indicated that the SAR increase is modest for all simulated underground mine scenarios and was maximum in the presence of a metal arch. At 868MHz, some observed that the SAR was greater in deep tissues of the head and torso as compared to SAR at 2.4GHz. Also, the torso is a better site for mounting wearable devices on the body to mitigate exposure.

Modeling the influence of rolled profile strengtheners on the arch support load-bearing capacity

Purpose.Increasing the load-bearing capacity of metal arch supports used to maintain the mine workings due to strengthening in places with the highest bending moment. Methods. The stress-strain state of the rock mass and support is analyzed using the ANSYS software package. The problem is studied in three variants: a support without strengtheners, a support with one strengthener in the area with the maximum bending moment, and a support with three strengtheners in the areas with the highest bending moments. To determine the bending moments and normal forces in a three-section metal arch support, the finite element method is used for specific and existing conditions, which is followed by the selection of the required standard size of the support. Findings. The conducted research gives reasons to believe that the proposed variant for increasing the load-bearing capacity of the support, made from a special replaceable rolled profile (SCP), can significantly improve the state of mine workings. Obviously, the proposed solution can be applied not only to arch supports, but also to other structures of rolled metal support. Originality. The pattern of changes in the values of internal forces arising in metal arch frame supports, depending on the deformation characteristics, the location of the strengtheners, as well as on the geometric characteristics of the mine working and the ratio of lateral and vertical loads on the support, has been determined. Practical implications. The proposed variant for increasing the load-bearing capacity of the support can be used to sustainably maintain mine workings in difficult mining-geological conditions of the Karaganda Coal Basin mines.

СУЧАСНИЙ СТАН КАПІТАЛЬНИХ ГІРНИЧИХ ВИРОБОК ТА ПРОПОЗИЦІЇ ЩОДО ПІДТРИМКИ ТА ПІДВИЩЕННЯ ЇХ СТІЙКОСТІ НА ПРАТ «ШУ «ПОКРОВСЬКЕ»

Purpose. Development and ground of rational parameters and energyeffective technologies of realization, method of guard and support of making are with the increase of depth of bedding. Methods. Further study of conformities to law of deformation of containing heterogeneous pedigree array and exposure of conformities to law of dynamics of the tensely-deformed state of containing array of making at the use of new methods of support or well-known with the changed parameters in certain geological terms on the basis of visual inspection and instrumental measuring of the mountain making at not in one’s dreams mountain pressure; comparative estimation of possible methods of support of making. Results. The improvement of the technology of installation and construction of the anchor-metal arch fastening when using the bearing capacity of the contour massif, taking into account its strengthening and unloading, is substantiated. Scientific novelty. Improvement of the design and technology of installation of anchor-metal arch fastening is based, in terms of the involvement of technical solutions, on increasing and using the bearing capacity of the near-contour massif, taking into account its unloading, based on modern research and many years of experience of PJSC “SHU “Pokrovske”. Practical significance. Achieving high rates of construction of capital and preparatory mining works, which ensure the highest production of coal in Ukraine. Keywords: mining, near-contour massif, methods of supporting mining, mining and geological conditions, anchor metal arch fastening.

EFFECT OF WELDING HEAT INPUT ON THE CORROSION RATE OF CARBON STEEL MMA WELDING

AbstractSteel is one of materials which often used on steel construction, bridge construction, and high rise building construction. Construction using welding joint is expected able to withstand construction loads for a long time. After a while weldment will be exposed to corrosion that will be construction failure in turn. One of the most important parameter in welding is heat input, however it hasn’t obtain correlation between heat input and corrosion rate on MMA (Manual Metal Arch) weldment on mild steel. This paper aims to obtain correlation between heat input and corrosion rate of low carbon steel with MMA welding. The result was show that corrosion rate tend to decrease with adding of duration, where higher corrosion rate at heat input 0,8108 kJ/mm was 68,68 gm/m2 hr at duration 5 hour.

MODERN IDEAS ABOUT THE SHAPE AND SIZE OF HUMAN DENTAL ARCHES

The study is devoted to the review of modern literature on the problem of analyzing the structural features of human dental arches. The aim of the work was to analyze the classifications of the forms of dental arches and the features of their parameters, taking into account the cranio-facial morphology. The features of 9 main forms of dental arches are presented according to the size of teeth and jaws. It is shown that the result of the compilation of dental and gnathic features is their division into dental arches of protrusion, mesotrusion and retrusion types. The designated varieties of forms of dental arches with a physiological occlusive norm are the criterion for choosing the prescriptions of braces and the size of metal arches in the treatment of dentition-alveolar forms of occlusion anomalies. Of particular importance are information about the shape of dental arches in determining the tactics of prosthetic treatment of patients with a complete absence of teeth, where the main reference point is the morphological features of the cranio-facial complex. Analysis of the literature proves the need for further research on the biometric features of dental arches, taking into account cranio-facial morphology, which is an urgent problem of morphology and clinical dentistry and has an important theoretical and applied significance.

Earth pressure distribution around flexible arch pipes

The Canadian Highway Bridge Design Code (CHBDC), the American Association of State Highway and Transportation Officials (AASHTO) and the Swedish Design Manual (SDM) are regarded as fundamental manuals for the design of flexible corrugated metal pipes. However, these manuals do not consider properly several factors that may affect the soil-structure interaction, such as the backfill soil stiffness, the pipe burial depth, the effect of compaction loads, and the trench geometry, including the trench width and the slope of the side of the excavation. To examine these factors, this paper utilizes a detailed finite element model of a flexible corrugated metal arch pipe. The model was developed and validated by using a field case study in Sweden. In a comprehensive parametric study, the numerical analysis and the empirical methods are used to investigate the applicability and accuracy of these methods for estimating the interaction behaviour of flexible culverts installed in semi-shallow and shallow trenches.

ПРОГНОЗ СРОКОВ БЕЗОПАСНОЙ СЛУЖБЫ ГОРНОКАПИТАЛЬНЫХ ВЫРАБОТОК

The paper presents the results of the study of the actual condition and service life of capital mine workings of the mine "Mnogovershinnoye". Typical forms of assessment of geo-logical conditions with subsequent estimation of the time of standing of the mine workings without support were established. The main types of supports and the character of their dis-turbance during the operation of workings have been determined with the subsequent sub-stantiation of the service life of mud-base concrete, metal arch and anchor supports under different conditions. On the basis of the commissioning date of capital mine workings at the mine "Mnogovershinnoe" a list of workings with the expired service life was made; there was stated the necessity of visual and instrumental examination of supports to assess their wear degree with the following repair-restoration works to maintain mine workings in the operable state.

ДОСЛІДЖЕННЯ ВПЛИВУ ПАРАМЕТРІВ ТЕХНОЛОГІЧНИХ СХЕМ ОЧИСНИХ РОБІТ НА СТІЙКІСТЬ ВИРОБОК ПРИ РЕАЛІЗАЦІЇ КОНЦЕПЦІЇ «МАЛИХ ШАХТ»

Purpose. Investigation of the influence of the parameters of technological schemes of coal mining on the stress-strain state of the rocks containing the mine roadways in the implementation of the concept of «small mines». Methods. The study used the finite element method and the analysis method. Modeling was carried out by the method of dangerous sections. According to the first variant of the technological scheme, two dangerous sections were selected, according to the second – four. The solution of the problem was carried out in a volumetric setting with observance of the boundary conditions. Results. The analysis of the stress-strain state of the rocks around mine roadways, according to the compared options, made it possible to determine the expected state of the rocks and establish the parameters of the zones of possible destruction. From the point of view of rock stability at the stage of elastoplastic deformation of rocks, the compared options are almost equivalent. Taking into account the shorter time of maintenance of roadways, it is more expedient to use short longwalls. In this version, trapezoidal support is used as the main fastening in the roadways, and in the “traditional” version – metal arch support. It is shown that with significantly lower costs for maintaining mine roadways, their stability when using short-longwall technological schemes is better. The studies carried out make it possible to assert that for “small mines” with small production, technological schemes with short longwalls are more appropriate than the “traditional” technological schemes developed for complex mechanization. Scientific novelty. The study of the stress-strain state of rocks around mine roadways of various shapes and sizes during the analysis of technological schemes for coal mining with short longwalls made it possible to establish the orientation and parameters of the massif sections that pass into an out-of-bounds state. This was done for the first time for the conditions of the Ukrainian Donbass. Practical significance. The availability of information about the expected stress-strain state of the rock mass allows timely planning of methods of fastening and measures to increase the local stability of rocks. Keywords: stresses, deformations, development, coal mine, technological schemes of excavation.

Reconstruction of an arched metal bridge over the Kineshemka River in the city of Kineshma, Ivanovo Region

This article discusses the technology of reconstruction of a metal arch bridge by reinforcing the structure with prestressed elements. The main metal beams were in unsatisfactory condition, the metal structures of the span below the level of the roadway slab are subject to deep layered corrosion up to the formation of through damage. To restore the bearing capacity of the main beams of the Nikolsky bridge across the Kineshemka river, their reinforcement is provided. The main task when performing the reinforcement of the main beams is the installation of new prestressed reinforced concrete beams directly inside the old metal main beams of the bridge with the regulation of forces in high-strength ropes. Due to the fact that the effort of high-strength ropes cannot be immediately brought to maximum design loads, a step-by-step prestressing scheme of ropes with synchronous sectional concreting of main beam compartments is proposed. The process of tension in the reinforced concrete beam of the main beams is carried out in two stages: stress at the end sections, where an anchoring system was created in four corners and then prestressing the main gift space with concreting sections between the pendants according to a specially developed scheme in the work design. Only fiber-reinforced concrete is used, and reinforcing stops were welded to work together with the inner surface of the main beams. Examples of reinforcing steel beams with steel strands on steel-reinforced concrete spans already existed, however, the transfer of force through a reinforced concrete inner beam was carried out for the first time in the world. After the main tie-in beams began to work together with a metal arch, it was decided to start repairing the cross-beams, which hold the reinforced concrete slab in the longitudinal direction, and themselves rely on the main beams. Some transverse beams were corroded to the point that they were holding onto a reinforced concrete slab, therefore NPP SK MOST developed a technology for prestressing the transverse beams with their jacking and subsequent shotcreting from all sides, and they were supported on the main beams, which were already ready for perception load. In conclusion, the authors confirm the effectiveness of the proposed technology; At the end of 2018, an examination and acceptance testing of the Nikolsky Bridge was carried out. The results of static and dynamic tests of the bridge indicate that the actual stress-strain state of the span structure is consistent with design values. The bridge can be taken under load NK-80. After the acceptance of the bridge structure by the working commission, traffic was opened for cars and pedestrians.

Analysis and Load Rating of Corrugated Steel Arch Culverts

ABSTRACTCulverts are typically used as short span bridge substitutes for spans less 50 ft (15 m). The corrugated metal arch culvert (CMAC) is one of the most popular types, which is frequently installed under highways, airport pavements and railroad tracks. For the purpose of validating the service conditions of CMAC, a load rating method is developed in this study based on AASHTO Manual for Bridge Evaluation. The rating factors (RFs) for culverts are derived to verify the capacity of the culverts to carry current standard truck loads. In order to carry out the load rating, a finite element model of the CMAC is developed for analysing the axial thrust of the culvert wall when subjected to static and dynamic moving truck loads. A method to calculate the CMAC wall thrust capacity is derived by summarizing existing capacity calculation approaches for arch culvert and corrugated metal plates.

Constructing Metal Arch Nanobridges Utilizing a Photothermal‐Induced Nanobonding Technique

AbstractConstruction of multilayered arch nanobridges and nanocantilever structures consisting of silver nanowires using a photothermal‐induced nanobonding technique is demonstrated. The fabricated nanobridges are of different height (300 nm to 20 µm) and span (25–70 µm). Their current–voltage characteristic curves indicate superior electrical connection between the metal nanowires and the abutments (gold thin film). Moreover, super mechanical strength of these arch nanobridges and nanocantilevers is demonstrated by putting gold nanoplates (a few tens of nm thick, a few tens of µm in diameter, and a maximum weight of 3 pN—about 20 times heavier than the silver nanowire of same length) on top of these nanostructures. The multilayered arch nanobridges demonstrate their potential applicability as short‐circuit‐free multipronged electronic connections in nanoelectronic devices. Furthermore, by recording the change in vibration frequency due to proximity of foreign contamination, these nanobridges and the nanocantilevers can be utilized to identify them; that is, these nanostructures can be used as biological sensors to detect viruses, bacteria, and other pathogens.

Analysis on Mathematical Models for the Protection Solutions of a Major Sewage Collector

The infrastructure development can lead to circumstances in which new roads affect the existing underground public facilities, serving the neighbouring areas. In order to connect the A3 highway with a main road in Bucharest, a new junction arm is planned, crossing on top one of the major existing sewage collectors (a 3.5 m diameter cylindrical structure made of precast segments with interior lining). The paper presents the numerical analyses using 2D of two protection solutions suggested for the collector: (1) a reinforced concrete slab supported on bored piles; (2) a self-standing reinforced concrete arch calotte. Concurrently, a third solution suggested by the contractor was dismissed (protection using a corrugated metal arch structure with independent foundations). All the loading conditions were considered: earth fill and road structure weight, traffic and exceptional water pressure inside the collector. The results (expressed by the annular and sectional stresses) were compared to the collector’s strength capacity. Advantages and disadvantages of each solution were emphasized and design recommendations for the protection structures were made.

Respiratory Exposure to Toxic Gases and Metal Fumes Produced by Welding Processes and Pulmonary Function Tests.

Background: Welding is a common industrial process and is harmful to welders' health. Objective: To determine the effect of toxic gases and metal fumes produced during 3 welding processes on welders' incidence of respiratory symptoms and pulmonary function. Methods:This cross-sectional study was conducted in an Iranian shipbuilding industrial factory in 2018. Using the simple census method, 60 welders were selected as the exposed group. 45 staff members of the administrative unit were also recruited to be served as the control group. Welders' demographic data and respiratory complaints were collected employing a questionnaire. Fumes and gases produced were sampled from the welders' respiratory tract and analyzed by standard methods suggested by the National Institute of Occupational Safety and Health (NIOSH). Pulmonary function test was also performed for each participant. Results: The prevalence of respiratory symptoms in all welders was significantly (p<0.05) higher than the control group. The mean FVC, FEV1 and FEV1/FVC measured in welders involved in all 3 processes were significantly lower than those recorded in the control group. The spirometry pattern in welders involved in flux cored arc welding and shielded metal arc welding was obstructive; that in those involved in gas metal arch welding was mixed (obstructive and restrictive pattern). Conclusion: Exposure to welding fumes and gases was associated with pulmonary function deterioration. Welders involved in gas metal arch welding had a prevalence of pulmonary disorders compared with those involved in gas metal arch welding and flux cored arc welding.