The development of subway and highway tunnels has led to the spatial intersection of tunnels, significantly impacting tunnel deformation, lining stress, and ground settlement during construction. To ...study the influence of critical parameters such as the cross angle and centre-to-centre distance on the tunnel performance, a series of numerical simulations were carried out. The influence range and magnitude of stress in the spatial cross tunnel under different cross angles were determined. The results indicated that as the crossing angle increased, the stress on the lining decreased, and the vault displacement increased. Meanwhile, the parallel tunnels showed opposite tendencies. Based on these results, the crossing angle of the cross tunnels was suggested to be greater than 45°. Parallel tunnels should be considered individually because the loading is symmetrically distributed. Considering the vault displacement and von Mises stress of the lining, it is recommended that the tunnel spacing be greater than 2D. The numerical model was validated against field data, and the findings of this study can be useful in designing cross tunnels.
Based on reinforced earth retaining wall of green gabion which is built at the site of seventh project Shaoxing-Zhuji Expressway, the research for soil pressure in a cross section which locate at the ...site of K38+398kmare made by field test and numerical analysis. The horizontal and vertical earth pressure are studied in the construction, The pressures between field test and numerical analysis which depend on FLAC3D are rough similar. With increased of height in filling soil, the earth pressures on the wall toe in 3 direction such as horizon , vertical, 45°are increased ,and then gradually come to stability after construction. With increased of height in filling soil, the vertical earth pressures is increased, but the distribution for earth pressure at the same height is non-uniform. The horizontal earth pressure on the back of wall surface increases fast at first then decreases a little, which is a single peak-shaped, it distributes along the wall height in non-linear form, the maximum occurs at 1/3H. The result between field test and numerical model are different, because the flexible wall surface has a great affection on unload.
Systematically analyzed the rock breakage process in borehole blasting, put forward the “dynamic and static press” breakage principle of rock borehole blasting. Use AUTODYN software to make borehole ...blasting numerical simulation, educed the single and double borehole blasting of rock breakage process and analyzed the borehole non-coupling charge blasting effect. At last, comparing theoretical analysis with numerical simulation methods in roof-weaken of coal mine by blasting, we got that the scene blasting fracture and monitoring coal mine press regulation verified the conclusion of study. The method not only plays a positive role in perfecting borehole blasting theory, but also verifies that the deep hole blasting in coal mine roof-weaken method is effective and feasible.
Slope failure disasters have been increasing in recent years, and although research on heavy rains and earthquakes that cause them is progressing, it is difficult to investigate the deformation ...mechanism inside slope that is the predisposing factor. Therefore, in order to deal with slope disasters, it is a agenda to evaluate complicated gravitational deformation mechanism inside the slope.Firstly, We confirmed that the balanced cross-section method can evaluate gravitational deformation mechanism inside a dangerous slope. Secondly, we developed a new finite element method （BaFEM） as a numerical analysis method that can reproduce the balanced cross-section method quickly and universally. In the balanced cross-section method, large deformation accompanied by displacement and separation of strata occurs. For this reason, it is difficult to replicate the balanced cross-section method with the previous finite element method. Therefore, we improved the previous finite element method and proposed a new method of creating and deleting contact elements repeatedly by separating the elements from a certain distance. And, complex gravitational deformed slope such as buckling and toppling, which cause slippage and separation, can be replicated, and the stress and share strain inside the slope during large deformation can be evaluated moment by moment.As a result, it is possible to predict not only the deformation mechanism but also the future deformation in the reproduction analysis of the actual gravitational deformation slope using BaFEM.
In this work Particle-in-Cell (PIC) simulation with the Monte Carlo collisions and the cumulative scattering angle coulomb collision are carried out to simulate the parallel transport of the plasma ...along the scrape-off-layer. The neutral gas pressure and temperature are fixed in front of the divertor target. We enhance the Coulomb collision inside the plasma so that the detached plasma can be observed. The various simulation runs is carried out by fixing the neutral gas pressure, PN = 10 mTorr and varied the Coulomb collision frequency. The strong electron temperature gradient forms inside the neutral gas region and the temperature goes below 1 eV at high Coulomb collision frequency. The detached plasma can be observed. The time evolution of the divertor heat flux strongly decreases during the detached state which cause by the strong e-i energy relaxation process.
The low cost and stable performance of steel dampers are frequently employed to reduce displacement and acceleration responses in an earthquake. Dampers cannot dissipate elastic energy but may ...increase a structure's absolute acceleration. To overcome these problems, the dampers can be designed for early yielding, so they may be damaged by a small earthquake. The authors have proposed Z-type and anti-Z-type NC braced frames that reduce elastic acceleration response by elastic energy accumulation due to incremental deformation. Residual deformation after an earthquake can be reduced by release of NC brace residual tension, so this system is superior to reuse performance. Qualitative performance of these frames is obtained from shaking table tests and numerical analyses, but quantitative estimation of the seismic response values is not clarified and differences among the seismic performances of these braced frames is not investigated. Seismic response estimation based on energy balance is often applied in the seismic design field. The concept of the method was proposed by Housner, and its usefulness for seismic response prediction was verified by Akiyama. The energy balance method is an efficient tool for evaluating accumulated plastic deformation and a structure's maximum deformation in an earthquake. In this paper, numerical analyses of these NC braced frames as well as an X-type brace are carried out to examine their seismic responses. A seismic response prediction method based on the energy balance principle is formulated and the method's accuracy is evaluated from numerical results. Conclusions are summarized as follows. 1) Z-type, anti-Z-type and X-type NC braced frames can reduce elastic acceleration response by elastic strain energy accumulation. From numerical results, Z-type and anti-Z-type frames can reduce by up to 40% maximum acceleration, and X-type frames can reduce by up to 22.8%. 2) Maximum responses of all braced frames under elastic vibrations have the following tendencies. Maximum acceleration is reduced in the order, X-type with initial tension, normal X-type and Z-type, and anti-Z-type. Maximum story-drift deformation of X-type is the same irrespective of initial tension. Maximum story-drift deformation and residual story-drift deformation of both Z-type and anti-Z-type frames are equivalent. 3) Maximum responses of each braced frame under elasto-plastic vibrations have the following tendencies. Both X-type and anti-Z-type frames show bi-linear cyclic curves around the origin and Z-type around δc* calculated by Eq.(1), and maximum acceleration and maximum deformation from the center of a cyclic curve. Maximum story-drift deformation and residual story-drift deformation of both Z-type and anti-Z-type frames are equivalent. 4) A seismic response prediction method based on the energy balance principle is formulated, and the maximum acceleration and maximum story-drift deformation of NC braced frames under elastic vibrations and residual story-drift deformation of Z-type and anti-Z-type frames can be predicted. All predictions of seismic responses are in good agreement with the corresponding numerical result. Reduction ratio of maximum acceleration by elastic strain energy accumulation can be calculated by the prediction method without numerical analyses. 5) Damage to the NC braced frames can be evaluated safely by the prediction method. The residual story-drift deformation of both Z-type and anti-Z-type frames under elasto-plastic vibrations can be accurately predicted.
In this paper, according to the special layout of the tilting grille unmanned aerial vehicle (UAV), the aerodynamic characteristics of the UAV was analyzed by computational fluid dynamics (CFD) ...method, and the result was validated through flight test. In CFD method, coordinate transformation and vector superposition were used to obtain the total aerodynamic force and moment characteristics. This method can substantially reduce the demand of computing resource. Based on the CFD result, the grille can reduce propeller actual pulling force, and the aerodynamic force and moment changed much. The flight test shows that the result of CFD can predict the flow characteristics and aerodynamic characteristics of the UAV during transition mode, and it can ensure the modeling precision for UAV flight control law design reference.
This paper introduced the finite element analyses into ergonomics designs of aluminum beverage can ends to evaluate perception of pressure applied to the human fingertip numerically and objectively. ...At first, experiments of indenting vertically the fingertip pulp by a probe and the tab of the can ends have been done to observe force responses and to experience feelings in the fingertip. It is found that a typical force-displacement curve can be divided into three parts according the curve gradient. We feel a touch at the first part of the force-displacement curve, and then feel pressure and our pulse at the second part, finally feel discomfort followed by pain at the last part. The finite element analyses have been performed to simulate the tab indenting the fin-gertip vertically for developing the finite element model of the fingertip. It is confirmed that the simulation results agree well with the experimental observations. Moreover, a simulation of finger lifting the tab of the can end has also been performed, and discomfort in the fingertip has been evaluated numerically to present the finger accessibility of the tab. Finally, the finger accessibility comparison of two kinds of tab ring shape designs showed that the finger accessibility of the tab that may have a larger contact area with the finger is better.
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