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In order to solve the problem of gas overrun in the fully mechanized caving face and the upper corner of high gas and extra-thick coal seam, the fracture and caving process of the roof in the goaf is analyzed and studied by using the relevant theories of fracture mechanics and seepage mechanics. The mathematical model of fracture and caving of the immediate roof and main roof in the goaf is established. Combined with ANSYS Fluent 6.3.26, the seepage process of gas in coal and rock accumulation in the goaf under different ventilation modes is simulated. The distribution law of gas concentration in the goaf is obtained, and the application scope of different ventilation modes is determined. In addition, the influence of the tail roadway application and the wind speed size on the gas concentration in the goaf and the upper corner of the fully mechanized caving face is also explored. The results show that, affected by wind speed and rock porosity, along the strike of the goaf, about 30 m near the working face, the gas concentration is low and growth is slow. In the range of 30~160 m, the gas concentration increases rapidly and reaches a higher value. After 160 m, the gas concentration tends to be stable. Along with the tendency of the working face, the gas concentration in the goaf increases gradually from the inlet side to the return side, and the gas concentration increases noticeably near the return air roadway. Along the vertical direction of the goaf, the gas concentration gradually increases, and the concentration of the fracture zone basically reaches 100%. Different ventilation modes have different application scopes. The U-type ventilation mode is suitable for the scenario of less desorption gas in the coal seam, while U + I and U + L-type ventilation modes are suitable for the scenario of more desorption gas in coal seam or higher mining intensity. The application of the tail roadway can reduce the gas concentration in the upper corner to a certain extent, but it has limited influence on the overall gas concentration distribution in the goaf. In addition, when the wind speed of the working face should be controlled at 2.0~3.5 m/s, it is more conducive to the discharge of gas, the method of reducing the gas concentration in the upper corner by increasing the wind speed of the working face is more suitable for the case where the absolute gas emission of the fully mechanized caving face is low, and the effect is limited when the absolute gas emission is high. The above conclusions provide a reference for solving the problem of gas overrun in the goaf and the upper corner of a fully mechanized caving face. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The immersed roller is very common in the roll-to-roll industry, such as hot dip galvanizing, electroplating, roll coating. In these applications, the strip is developing thinner and wider, and its flexibility is also strengthening. The vibration of the sinking roller has an increasingly significant impact on its product quality. A theoretical model was established to study the sink roller immersed in fluids, and modal tests and corresponding finite element simulations were carried out to study the sink roller's characteristics. The effects of roller density, wall thickness, fluid density, viscosity, and constraint conditions on modal characteristics were investigated. The results were well-validated, and the modal tests in air with and without a rod have high consistency, proving the reliability. The first six peak values of FRF curves are clear when immersed in water and hydraulic oil, but only the first three are evident in glycerin. It is observed that the viscosity of glycerin has a minor effect on natural frequencies, but the added damping factor grows when viscosity increases. The added mass factor rises linearly with the growth of wall thickness or liquid density while decreasing when the structure's density increases. The added mass factors of the (1,2)th and (2,2)th modes are more significant than the bending modes. A rigid-body displacement occurs at the constrained end journal of bending mode for rollers in liquids. Liquid density is the main factor affecting natural frequencies, especially for aluminum rollers. The maximum frequency growth rates under the constrained state of the steel and aluminum rollers in water are 5.7% and 20.4%, respectively, on the (2,2)th mode. Moreover, it increases with the increase of liquid density and viscosity, which leads to higher resonance probability. It can provide a basis for the dynamics research of similar systems. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Piping-seepage damage is one of the major factors leading to tailings dam failure. To explore the microscopic influence mechanism of tailings with different fine content on piping development, on the basis of the indoor permeability test, combined with the coupling method of discrete particle flow at the microlevel, through the small seepage model test, the discrete element model of the model test was further constructed. The effects of different fine particle contents on particle size composition, permeability, critical water head, fine particle migration, and porosity of samples were analyzed by an indoor small-scale seepage model and the corresponding numerical simulation study. The results showed that before the occurrence of piping, with the increase of fine particle content, the gradation constant is less than 0.074 mm, and the downward trend changes abruptly, showing a concave curve change. The permeability coefficient showed a decreasing trend, and the critical water head increased. The maximum void ratio and the minimum void ratio generally decreased first and then increased. The strong force chain decreased, and the total force chain increased; there were obvious differences in the change of porosity of different fine particle contents before, during, and after destruction. This was verified by the indoor physical model test that different fine particle contents will lead to different sand inflows in seepage dam break. In practical engineering, it is more helpful to provide a new way for the comprehensive prevention of seepage failure of tailings dam by clarifying the disaster-causing mechanism of piping and seepage failure of tailings dam from the mesostructure. [ABSTRACT FROM AUTHOR]

The purpose is to investigate the response of the surrounding rock mass's seepage field, displacement field, and stress field during dynamic tunneling in soft soil. Relied on a large-diameter river-crossing shield tunnel project, considering driving force, shield tail grouting pressure, and the friction resistance between the shield shell and the soil, a three-dimensional fine tunnel model taking into account the liquid-solid coupling effect (LSCE) in the soil during dynamic tunneling was established by employing the finite difference method. The response characteristics of pore water pressure(PWP), displacement and stress in the surrounding rock mass were obtained. The results show that due to the liquid-solid coupling(LSC) in the surrounding rock mass, the PWP in the range of 0.5 times the hole diameter around the tunnel reduces and increases, respectively, during shield tunneling and shield tail grouting. The PWP of the soil close to the vault falls as the shield tunneling recedes, whereas the PWP close to the tunnel arch bottom rises. The impact range of shield tail grouting on the vertical settlement of the overlying soil is about 0.5 times the hole diameter. The shield tail grouting can significantly lessen the vertical settlement of the overlying soil and moderate the vertical uplift of the bottom soil. During shield tunneling the vertical stress distribution of the soil above the vault of the working position and around the excavation surface is funnel-shaped, and the vertical stress around the excavated tunnel decreases. [ABSTRACT FROM AUTHOR]

Aiming to solve the problem of oil-air lubrication failure caused by the high working temperature of high-speed rolling bearings, this study proposes a method, based on the theory of gas-solid two-phase flow and bearing tribology, of predicting the dynamic temperature rise of nonlinear high-speed rolling bearings under oil-air lubrication conditions. The accuracy of the fluid–structure coupling model is verified by comparing the temperature rise test results of angular contact ball bearing at different speeds. The characteristics of oil-air lubrication circulation and the relationship between the lubrication parameters and the heat balance of the high-speed rolling bearings have been studied. The results show that the gas supply pressure of the system has a significant influence on the continuity and fluctuation of the oil film in the oil pipe nozzle. The initial rise in temperature of the inner and outer rings of the bearing and the fluid domain has a speed threshold value, and the temperature increases linearly with the bearing speed. With the increase in the oil supply and lube oil viscosity of the system, the temperature rise of the outer ring of the bearing increases first, then decreases, and finally increases again. There is an optimal oil supply 5.5 mL and optimize viscosity 68 cSt for the bearing in the work condition. [ABSTRACT FROM AUTHOR]

How to effectively reduce the sloshing wave height of the liquid is an important direction for the optimal design of the steel liquid storage structure. To find the optimal design for structure with reduce liquid sloshing, the liquid–solid coupling seismic responses of steel rectangular water purification structure (SRWPS) under different opening arrangements in a partition are studied. Based on the finite element method, the arrangements of the No. 11 partition with 2, 4 and 6 holes are selected as the parameters to study how the variation of liquid sloshing wave height, the wall displacement and the stress change with the number of holes in the partition. The results show that the liquid sloshing height is significantly reduced and the deformation of the wall of SRWPS is small when the partition plate with holes compared to non-perforated partitions. With the increase of holes in the No. 11 partition, the magnitude of the principal stress shows an increasing trend. This means that the tensile strength of the partition itself needs to be focused on when designing the openings of a partition to avoid tensile damage to the partition. However, when the number of partition openings is controlled in a certain range, the overall strength of the structure is less affected due to the synergy of functional partition and perforated baffles. The 4-hole layout scheme of the No. 11 partition is the best solution to reduce liquid sloshing, as determined by comparing the liquid sloshing wave height, the wall deformation, the stress state and the partition displacement of SRWPS under different opening schemes. The hole layout scheme proposed by this paper provides a new perspective for the SRWPS reducing sloshing analysis. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the effect of the multi-directional components of ground motion on an unanchored steel storage tank. Both the liquid sloshing effect and contact behavior between the foundation and tank are included in the study. A three-dimensional model for a foundation–structure–liquid system is numerically simulated using the finite element method. The Lagrange fluid finite element method (FEM) in ANSYS is used to consider the liquid–solid interaction. In the liquid–structure–foundation interaction model, the contact and target elements are adapted to simulate the nonlinear uplift and slip effects between the tank and the foundation. Three earthquake ground motions are selected for evaluating the seismic behavior of the tank. Comparisons are made on the horizontal displacement, "elephant-foot" deformation, stress, base shear and moment, sloshing of the liquid, uplift, as well as slip behavior under the application of the unidirectional, bi-directional and tri-directional components. Under the selected ground motions, the horizontal bi-directional seismic component has great influence on the liquid sloshing in the tank studied in this paper. The vertical seismic component produces high compressive axial stress, and it also makes the uplift and slide of the tank bottom increase significantly. The applicability of this conclusion should be carefully considered when applied to other types of ground motion inputs. [ABSTRACT FROM AUTHOR]

Damage identification for liquid–solid coupling structures remains a challenging topic due to the influence of liquid and the limitation of experimental conditions. Therefore, the adding mass method for damage identification is employed in this study. Adding mass to structures is an effective method for damage identification, as it can increase not only the experimental data but also the sensitivity of experimental modes to local damage. First, the fundamental theory of the adding mass method for damage identification is introduced. After that, the method of equating the liquid to the attached mass is proposed by considering the liquid–solid coupling. Finally, the effectiveness and reliability of damage identification, based on adding mass for liquid–solid coupling structures, are verified through experiments of a submerged cantilever beam and liquid storage tank. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There is a strong fluid-solid coupling effect during the process of coal seam pulse water infusion. Based on the basic principle of liquid-solid coupling, the dynamic damage evolution rule during coal seam pulse water infusion is simulated through secondary development of ABAQUS software. During this process the mathematical model of the strain accumulation model due to the periodic changes of pulse water pressure is embedded in SOIL module of ABAQUS software discussed in this paper, in order to obtain the dynamic damage evolution rule of coal seam around the pulse water infusion hole. It provides a new quantitative method of determining coal seam pulse water infusion parameters and location. The law of different parameters of pulse water infusion on the dynamic damage evolution of coal around the infusion hole is gotten. Numerical simulation results show that, during the process of coal seam high pressure pulse water infusion, the stress field and flow field are mutual influence and mutual restriction. The coupling of the stress and flow field have impact on the physical and mechanical properties of coal in front of the working face, these factors promote each other and prevent coal and gas outburst effectively. The coal damage quantity increases significantly with the water infusion time prolonging under constant water infusion pressure and frequency. The coal damage quantity increases significantly with the water infusion pressure increasing under constant water infusion time and frequency. The coal damage quantity increases significantly with the water infusion frequency increasing under constant water infusion pressure and time. So the pulse water infusion time needs to ensure a better effect of preventing coal and gas outburst is gotten. Meanwhile the pulse water infusion pressure needs to improve under the existing technical conditions. The frequency of pulse water infusion needs to improve under the existing technical conditions. This research results contribute to obtain accurate dynamic distribution law of damage fields around water infusion holes. It provides theoretical basis for optimizing pulse water infusion in technological parameters design and raising water infusion effect. [ABSTRACT FROM AUTHOR]

To study the seismic response of a liquid-solid coupling in an isolated concrete rectangular liquid-storage structure under small amplitude sloshing, a three-dimensional model of the isolated concrete rectangular liquid-storage structure was established based on the assumption that the concrete is considered to be a linear elastic material. The seismic responses of the isolated concrete rectangular liquid-storage structure with the same liquid sloshing height under different seismic intensities and different liquid heights under the same earthquake wave were studied. The results show that the seismic responses of the rectangular liquid-storage structure are different in the cases of small amplitude sloshing and linear elastic material with different seismic intensities due to the effects of the seismic wave frequency domain and time domain characteristics. At the same liquid height, the wall displacement, the liquid sloshing height and the equivalent stress of the isolated concrete rectangular liquid-storage structure are increased as the seismic intensity increases. The liquid height has a certain effect on the seismic responses of the liquid-storage structure, and when the liquid height is lower, the peak values of the liquid sloshing height, the wall displacement and equivalent stress are greater. [ABSTRACT FROM PUBLISHER]

It is very important for mine production safety to ensure the stability of the tailings dam. Taking a flatland tailings pond as the background, a threedimensional computational model was built based on a tailings dam under mullock heap preloading condition. Considering the current operating water level conditions, a liquid-solid coupling analysis of the model was conducted. The deformation characteristics of the tailings dam were revealed during successive preloading at the front of the dam. The safety factor and the potential slide face of the tailings dam were calculated under different conditions using the strength reduction method. The results show that the tailings dam in its current condition is basically stable, but if the mullock heap continues to be heightened, the tailings dam will become unstable. Therefore, in order to limit the height of the mullock heap, establishing a monitor and early warning mechanism are put forward to ensure mine production safety. [ABSTRACT FROM AUTHOR]