On the basis of the three-dimensional(3D)random aggregate&mortar two-phase mesoscale finite element model,C++programming was used to identify the node position information of the interface between the aggregate an...On the basis of the three-dimensional(3D)random aggregate&mortar two-phase mesoscale finite element model,C++programming was used to identify the node position information of the interface between the aggregate and mortar elements.The nodes were discretized at this position and the zero-thickness cohesive elements were inserted.After that,the crack energy release rate fracture criterion based on the fracture mechanics theory was assigned to the failure criterion of the interface transition zone(ITZ)elements.Finally,the three-phase mesomechanical model based on the combined finite discrete element method(FDEM)was constructed.Based on this model,the meso-crack extension and macro-mechanical behaviour of coral aggregate concrete(CAC)under uniaxial compression were successfully simulated.The results demonstrated that the meso-mechanical model based on FDEM has excellent applicability to simulate the compressive properties of CAC.展开更多
Based on the flux equivalent principle of a single fracture, the discrete fracture concept was developed, in which the macroscopic fractures are explicitly described as （n-l） dimensional geometry element. On the fun...Based on the flux equivalent principle of a single fracture, the discrete fracture concept was developed, in which the macroscopic fractures are explicitly described as （n-l） dimensional geometry element. On the fundamental of this simplification, the discrete-fractured model was developed which is suitable for all types of fractured porous media. The principle of discrete-fractured model was introduced in detail, and the general mathematical model was expressed subsequently. The fully coupling discrete-fractured mathematical model was implemented using Galerkin finite element method. The validity and accuracy of the model were shown through the Buckley-Leverett problem in a single fracture. Then the discrete-fractured model was applied to the two different type fractured porous media. The effect of fractures on the water flooding in fractured reservoirs was investigated. The numerical results showed that the fractures made the porous media more heterogeneous and anisotropic, and that the orientation, size, type of fracture and the connectivity of fractures network have important impacts on the two-phase flow.展开更多
In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,...In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,wave propagation in the infinitely extended ground is dealt with using a simple,yet efficient gradually damped artificial boundary.Based on the assumption of invariant geometry and material distribution in the tunnel's direction,the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number.Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number.The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform.The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum.A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.展开更多
基金supported by the Key Projects of the National Science Foundation of China(Nos.52178190,52078250,11832013)
文摘On the basis of the three-dimensional(3D)random aggregate&mortar two-phase mesoscale finite element model,C++programming was used to identify the node position information of the interface between the aggregate and mortar elements.The nodes were discretized at this position and the zero-thickness cohesive elements were inserted.After that,the crack energy release rate fracture criterion based on the fracture mechanics theory was assigned to the failure criterion of the interface transition zone(ITZ)elements.Finally,the three-phase mesomechanical model based on the combined finite discrete element method(FDEM)was constructed.Based on this model,the meso-crack extension and macro-mechanical behaviour of coral aggregate concrete(CAC)under uniaxial compression were successfully simulated.The results demonstrated that the meso-mechanical model based on FDEM has excellent applicability to simulate the compressive properties of CAC.
基金supported by the National Basic Research Program of China("973"Program)(Grant No.2011CB20100)the Important National Science and Technology Project of China(Grant No.2011ZX05014- 005-003HZ)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20090133110006)the Fundamental Research Funds for the Central Universities(Grant No. 09CX04005A)
文摘Based on the flux equivalent principle of a single fracture, the discrete fracture concept was developed, in which the macroscopic fractures are explicitly described as （n-l） dimensional geometry element. On the fundamental of this simplification, the discrete-fractured model was developed which is suitable for all types of fractured porous media. The principle of discrete-fractured model was introduced in detail, and the general mathematical model was expressed subsequently. The fully coupling discrete-fractured mathematical model was implemented using Galerkin finite element method. The validity and accuracy of the model were shown through the Buckley-Leverett problem in a single fracture. Then the discrete-fractured model was applied to the two different type fractured porous media. The effect of fractures on the water flooding in fractured reservoirs was investigated. The numerical results showed that the fractures made the porous media more heterogeneous and anisotropic, and that the orientation, size, type of fracture and the connectivity of fractures network have important impacts on the two-phase flow.
基金Project supported by the National Natural Science Foundation of China (Nos. 51178418 and 51222803)the National Key Technology R&D (863) Program of China (No. 2009BAG12A01-B12-3)
文摘In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,wave propagation in the infinitely extended ground is dealt with using a simple,yet efficient gradually damped artificial boundary.Based on the assumption of invariant geometry and material distribution in the tunnel's direction,the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number.Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number.The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform.The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum.A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.
