The shallow tunnelling method (STM) often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load. The complex support system ...composed of primary and temporary supports can ensure safety during tunnel construction. Based on the large section tunnel of Beijing Subway Line 12, the mechanical characteristics of support system by the double‐side‐drift method (DSDM) during excavation and demolition were analyzed through numerical simulation and monitoring. The study showed that the middle cave excavation was the most critical stage of the DSDM, during which the load on the supporting structure increased significantly. The temporary vertical support bore most of the new load during middle cave excavation. During the demolition stage, the load was redistributed, which caused arch settlement and section convergence. The removal of the temporary vertical support exerted the greatest impact in this process. The lateral temporary inverted arch changed from axial compression to axial tension after the middle and lower caves were excavated. Based on the mechanical characteristics of the support system, some engineering suggestions were proposed for large section tunnel construction. These research results can provide reference for the design and construction of similar large section tunnels.
When faced with engineering problems with large sections and complex stratum conditions, the shallow tunnelling method (STM) often uses various temporary supports to divide the large section into several smaller closed or semi‐closed sections so that the bearing pressure of the unclosed support structure could be shared. In the process of construction, the dynamic evolution in mechanical properties of complex supporting structures needs to be studied. Taking a large section tunnel of Ji‐Bei Inter‐district Tunnel of Beijing Subway Line 12 as the research object. through numerical simulation and field monitoring, analyze the grille steel frame and I‐beam during construction. Further study of the double‐side‐drift method (DSDM) support system in excavation and demolition phases of the mechanical characteristics, summarizes the key construction behaviors of DSDM. Some engineering suggestions are put forward for the construction of large section tunnel, which can provide theoretical reference for the design and construction of large section tunnel under similar geological conditions.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Water splitting is an effective approach to produce hydrogen. The direct electrocatalysis of seawater can avoid the use of limited freshwater resources and facilitate large-scale hydrogen production, ...but stable and efficient electrocatalysts are essential and still challenging. MOF derivatives supported on conductive substrates exhibit promising performances for water splitting. Therefore, we present a two-step approach to construct hierarchical N-doped carbon nanotubes encapsulating Mn3Co7 nanoparticles frameworks by pyrolyzing CoMn-MOF grown on nickel foam. In 1.0 M KOH, the catalyst demonstrates remarkable electrocatalytic performance with low overpotentials of 115 and 210 mV for HER and OER, respectively, and achieves a cell voltage of 1.60 V at 10 mA·cm–2 for overall water splitting. For seawater splitting, it shows promising HER activity with overpotentials of 130 and 306 mV at 10 and 200 mA·cm–2 in alkaline seawater. More importantly, in natural seawater, the catalyst exhibits excellent stability and attractive HER overpotential of 331 mV at 10 mA·cm–2, due to regulatory strategies on metal nanoparticles such as CoMn bialloying, space dispersion and charge transport by carbon nanotubes, carbon layers’ encapsulation, and protection. Our work offers a potential approach to synthesizing self-supporting multimetallic nanocarbon materials for seawater splitting and electrochemical energy devices.
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IJS, KILJ, NUK, PNG, UL, UM
Although mold designs are used in various sectors, molding composite materials results in issues such as deformation and insufficient stiffness. To this end, the response surface method was used to ...optimize the design of the mold support structure partition, improving the performance parameters of the mold by increasing the number of U and V direction partitions. The experiment showed that the deformation during forklift transportation decreased by 36.5%, during lifting transportation by 13.9%, during paving deformation by 36.9%, and during hot pressing, the deformation of the tank was reduced by 18.2%. After optimization, the maximum deformation of the mold under conditions such as forklift transportation, lifting, and paving is similar to or slightly reduced from the original model. Meanwhile, the thermal deformation and quality of the mold decreased by 28% and 12.8%, respectively. The research results have important reference value for the design of composite material forming molds, helping to improve the performance and efficiency of the molds and reduce costs. By optimizing the design of the support structure partition, effective control of mold deformation can be achieved, and the stiffness of the mold can be improved, thereby ensuring the stability and reliability of the mold under various working conditions.
In this research, we propose a topology optimization method for obtaining optimized structures satisfying a self-supporting property. First, we propose an artificial physical field that can detect ...structural components lacking the self-supporting property. Next, a level set-based topology optimization method is introduced, and we formulate the optimization problem, where the geometrical constraint function is defined with the artificial physical field. As a representative example of the optimization that requires the self-supporting constraint, we target an acoustic cloaking problem, and an objective function is defined with an acoustic pressure. The explicit formula of the design sensitivity is offered, which is based on the concept of the topological derivative. Several numerical examples are offered to confirm the validity and effectiveness of the proposed method. We show the characteristic of the proposed artificial physical field and conduct topology optimization for an acoustic cloaking structure without any unsupported structures.
The conventional additive manufacturing methods normally produce complex shape parts layer by layer. If there has suspended position, the supporting structure needs to be added. In this paper, a new ...method of tangential additive manufacturing based on multiaxis and contour blades is proposed. The technical principle and process flow were introduced. The processing of reconstructing new contour surface, the trajectory information of blade on print head, and the control method of multiaxis motion were investigated. A prototype was produced by the self-developed equipment. Under the action of the multiaxis system, the print head could be moved flexibly to the specified position and angle. During the tangential additive manufacturing process, the forming material extruded through the nozzle was constrained and supported by the contour blades, which could avoid using the supporting structure. The adjacent layers were bonded together by edges alignment. The results show that the tangential additive manufacturing based on multiaxis and contour blades could increase the production efficiency and avoid the staircases and the supporting structure synchronously, which would have good potential for future applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Purpose. This study is aimed at highlighting the features of determining the longitudinal load of the supporting structure of a flat car loaded with a piggyback under operating conditions and ...substantiating the possibility of using a flat car model 13-401 for transportation of piggyback. Methodology. Mathematical modeling of the dynamic loading of the supporting structure of a flat car model 13-401 loaded with a piggyback was carried out. Two schemes of interaction between the piggyback and the supporting structure of the flat car are taken into account: the lack of movements of the piggyback relative to the frame of the flat car during movement and the presence of movements of the piggyback relative to the frame of the flat car during movement. Solution of the differential equations is implemented in the MathCad software. The obtained accelerations were taken into account motion when calculating the strength of the supporting structure of the platform car. The strength calculation of the supporting structure of the platform car was carried out. Obtained accelerations are taken into account to calculate the strength of supporting structure of the flat car. Findings. Based on the mathematical modeling of the dynamic loading of supporting structure of the flat car, it was found that in the absence of piggyback movements relative to the flat car frame, the maximum acceleration was 32 m/sec2. If the piggyback moves relative to the flat car frame, the maximum acceleration acting on the supporting structure is about 40 m/sec2, and about 42 m/sec2 on the piggyback. The main strength indicators of the supporting structure of the flat car are determined. It was established that the maximum equivalent stresses in this case arise in the cantilever parts of the center sill and are about 315 MPa, that is, do not exceed the permissible ones. The maximum displacements in the structure nodes are 2.6 mm, the maximum deformations are 2.5 ∙ 10-2. Originality. The mathematical model of the dynamic loading of supporting structure of a flatcar loaded with a piggyback is improved. At the same time, the rigid piggyback fastening to the flat car frame, as well as the flexible one, is taken into account. For the first time, a computer model has been developed to determine the strength of the supporting structure of a flat car during the piggyback transportation. The model makes it possible to determine the strength main indicators of supporting structure with its longitudinal loading. Practical value. The conducted studies allow us to conclude that the transportation of piggyback on the flat car model 13-401 is possible. The results of the studies will contribute to the creation of recommendations on the flat car design for piggyback transportation, and can also be useful developments when creating removable means of piggyback transportation.
Мета. Це дослідження спрямоване на висвітлення особливостей визначення поздовжньої навантаженості несучої конструкції вагона-платформи, завантаженого контрейлером, за експлуатаційних режимів та обґрунтування можливості використання вагона-платформи моделі 13–401 для перевезення контрейлерів. Методика. Проведено математичне моделювання динамічної навантаженості несучої конструкції вагона-платформи моделі 13–401, завантаженого контрейлером. До уваги взято дві схеми взаємодії контрейлера з несучою конструкцією вагона-платформи: відсутність переміщень контрейлера відносно рами вагона-платформи під час руху, а також наявність переміщень контрейлера відносно рами вагона-платформи під час руху. Розв’язок диференціальних рівнянь руху здійснено в програмному забезпеченні MathCad. Отримані прискорення враховано для розрахунку на міцність несучої конструкції вагона-платформи. Результати. На підставі проведеного математичного моделювання динамічної навантаженості несучої конструкції вагона-платформи встановлено, що за відсутності переміщень контрейлера відносно рами вагона-платформи максимальне прискорення складає 32 м/с2. За наявності переміщень контрейлера відносно рами вагона-платформи максимальне прискорення, яке діє на несучу конструкцію, складає близько 40 м/с2, а на контрейлер – близько 42 м/с2. Визначено основні показники міцності несучої конструкції вагона-платформи. Установлено, що максимальні еквівалентні напруження при цьому виникають у консольних частинах хребтової балки та складають близько 315 МПа, тобто не перевищують допустимі. Максимальні переміщення у вузлах конструкції складають 2,6 мм, максимальні деформації – 2,5 ∙ 10-2. Наукова новизна. Доопрацьовано математичну модель динамічної навантаженості несучої конструкції вагона-платформи, завантаженого контрейлером. При цьому враховано жорстке закріплення контрейлера відносно рами вагона-платформи, а також податливе. Уперше розроблено комп’ютерну модель для визначення міцності несучої конструкції вагона-платформи під час перевезення контрейлера. Модель дозволяє визначити основні показники міцності несучої конструкції за її поздовжньої навантаженості. Практична значимість. Проведені дослідження дозволяють зробити висновок, що перевезення контрейлерів на вагоні-платформі моделі 13–401 є можливим. Отримані результати сприятимуть створенню рекомендацій щодо проєктування вагонів-платформ для контрейлерних перевезень, а також можуть бути корисними напрацюваннями для створення зйомних засобів контрейлерних перевезень.
In this paper, a novel method to fabricate quartz glass electromagnetically actuated ring resonator for gyroscope application is presented. Sacrificial supporting structures were employed for the ...fabrication. The fabricated device was electromagnetically driven at resonance, with the resonant frequency of 42 KHz. The Q-factor at the atmospheric pressure was about 142. The frequency difference between primary and secondary mode was 681 Hz.
This study delves into the design and deformation patterns of support structures in urban deep excavation projects, aiming to optimize the design of these structures to ensure their safety and ...stability. Initially, experimental research on steel-cement soil composite beams reveals their bending resistance and ductility under various loading conditions, confirming the effectiveness of the Soil Mixing Wall method in enhancing the stability of support structures. Subsequently, theoretical calculations using the method of elastic support points were conducted and validated through a deep excavation project in Xi’an, demonstrating that this method accurately calculates the trends of horizontal displacement in support structures. Additionally, FLAC 3D numerical simulations are utilized to analyze the patterns of horizontal and vertical displacement during the excavation process. The simulation results generally align with the actual measured data, showing that the support structures optimized by the elastic support points method effectively control horizontal displacement (maximum displacement of 47.8 mm) and vertical displacement (maximum heave of 67.3 mm), validating the effectiveness of the numerical simulation methods. This research not only provides theoretical and practical guidance for deep excavation projects but also holds significant reference value for the design and construction of similar engineering projects.
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