This paper has probed into the evolution of the hysteresis curve of rock under the cyclic loading by the experimental research on the deformation characteristics of sandstone under cyclic loading in three axial stress...
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This paper has probed into the evolution of the hysteresis curve of rock under the cyclic loading by the experimental research on the deformation characteristics of sandstone under cyclic loading in three axial stress levels. The research results have been indicated as follows on whether the hysteresis curve change will depend on the stress level: when the stress level is low, the acreage closed in the hysteresis curve will go invariable with the increase of cyclic count, but when the stress level is high, the acreage closed in the hysteresis curve will be variable from decrease to unchange and then to increase with the increase of cyclic count.
In this paper, integrating the principium of demolition blasting of buildings and the practice, the general mechanism and affection factors of blasting harms such as blasting shock, collapsing shock, blasting rock, bl...
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In this paper, integrating the principium of demolition blasting of buildings and the practice, the general mechanism and affection factors of blasting harms such as blasting shock, collapsing shock, blasting rock, blasting shock wave and blasting noises produced in demolition blasting of buildings are analyzed. The safety problems which existed in demolition blasting of buildings are discussed from three aspects such as the unsafe behavior of 'person', the unsafe state of 'substance' and the unsafe condition of 'environment'. Based on an engineering example, the difficulty of safety blasting of engineering example was analyzed, on this basis, corresponding effective safety defending measures and the method of safety control are brought forward. This study is significant to the construction safety and control of demolition blasting of similarity tower building in practice.
The method for extracting velocity field is mainly investigated and the image-processing system of two-dimensional Digital Particle Image Velocimetry (DPIV) is developed. The algorithm is based on gray image cross-cor...
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The method for extracting velocity field is mainly investigated and the image-processing system of two-dimensional Digital Particle Image Velocimetry (DPIV) is developed. The algorithm is based on gray image cross-correlation and the most similar sub-windows on the two frames in serial gray images are reckoned as optimal matching. The displacement of the particle movement on image plane is thus determined by the distance of the two centers of sub-windows. On basis of large amount of experimental results, the normalized cross-correlation coefficient is selected as the cross-correlation measure, which greatly reduces the computational time and meanwhile holds the particle matching accuracy. Moreover, the search regions are optimized to reduce time consumption. The experimental results of standard images as well as the successful application in the actual experiment of oxidation ditch model prove that the researched algorithm of velocity extraction is suited for the measurement of the flow field such as oxidation ditch model.
Based on the microstructure-mechanisms of rock materials and a simple mechanical model, a rheology damage constitutive equation is proposed by introducing generalized time defined in the space of irreversible strain a...
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Based on the microstructure-mechanisms of rock materials and a simple mechanical model, a rheology damage constitutive equation is proposed by introducing generalized time defined in the space of irreversible strain and Newtonian time, and an anisotropic damage tensor of rank four. The anisotropic evolution and unilateral effect of damage as well as the effect of hydrostatic pressure' can be taken into account in the proposed model. The corresponding numerical analysis is developed;and the creep, inelastic and damage behaviors of claystone are analyzed. It shows that the calculated results agree well with the experimental observation. The influence of stress level on the creep can be well described with the model.
Based on the fundamental principle of rock mechanics, the stresses of single joint rock mass under three-dimensional compression were analyzed. The effect of the in-termediate principle stress on the strength of singl...
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Based on the fundamental principle of rock mechanics, the stresses of single joint rock mass under three-dimensional compression were analyzed. The effect of the in-termediate principle stress on the strength of single joint rock mass were discussed in par-ticular. It is found that the strength of single joint rock are affected by the intermediate principal stress, which may be the main factor in some conditions.
Based on the mechanical experiment of brittle coal-rock and the damage mechanical theory, a damage model was established. Coal-Rock damage mechanical characteristic was researched. Furthermore, interior energy transfo...
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Based on the mechanical experiment of brittle coal-rock and the damage mechanical theory, a damage model was established. Coal-Rock damage mechanical characteristic was researched. Furthermore, interior energy transformation mechanism of rock was analyzed from the point of view of damage mechanics and damage energy release rate of brittle coal rock was derived. By analyzing the energy transformation of rock burst, a new conception, damage energy index of rock burst, was put forward. The condition of rock burst was also established.
A computational fluid dynamics (CFD) method is developed to investigate the radical motion of single cavitating bubble in the oscillating pressure field of a cavitating water jet. Regarding water as a compressible flu...
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A computational fluid dynamics (CFD) method is developed to investigate the radical motion of single cavitating bubble in the oscillating pressure field of a cavitating water jet. Regarding water as a compressible fluid, the simulation is performed at different oscillating frequencies. It is found that the bubble motion presents obvious nonlinear feature, and bifurcation and chaos appear on some conditions. The results manifest the indetermination of the cavitating bubble motion in the oscillating pressure field of the cavitating water jet.
a damage constitutive model comprising two dynamite sticks is established and handled with the transient dynamics finite element computer program PRONTO-3D to study rock damage and fragmentation during blasting. Simul...
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a damage constitutive model comprising two dynamite sticks is established and handled with the transient dynamics finite element computer program PRONTO-3D to study rock damage and fragmentation during blasting. Simulation tests find that tensile stress by detonation gives rise to tensile bulk strain and consequently damage in the material. Maximum bulk strain is observed in simultaneous detonations of the two dynamite sticks. It is demonstrated that the proposed method is applicable to studying the process of rock damage by blasting as well as its affecting factors.
Based on the new viewpoint of solid and gas interaction mechanics, gas leakage in a double deformable coal seam can be understood. That is, under the action of geophysical fields, the methane flow in a double deformab...
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Based on the new viewpoint of solid and gas interaction mechanics, gas leakage in a double deformable coal seam can be understood. That is, under the action of geophysical fields, the methane flow in a double deformable coal seam can be essentially considered to be compressible with time dependent and mixed permeation and diffusion through a pore cleat deformable heterogeneous and anisotropy medium. Based on this new viewpoint, a coupled mathematical model for coal seam deformation and gas leakage in a double coal seam was formulated and numerical simulations for gas emission from the coal seam are presented. It is found that coupled models might be closer to reality.
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