Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress ...Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress and displacement, after that, a boundary value problem with unified model was formed and solved. Ultimately, an applied numerical simulation system was developed. It was compared with the model having analytical solution for verifying the applicability and the calculating precision.展开更多
The indirect boundary element method （IBEM） is developed to solve the scattering of plane SH-waves by a lined tunnel in elastic wedge space. According to the theory of single-layer potential, the scattered-wave fiel...The indirect boundary element method （IBEM） is developed to solve the scattering of plane SH-waves by a lined tunnel in elastic wedge space. According to the theory of single-layer potential, the scattered-wave field can be constructed by applying virtual uniform loads on the surface of lined tunnel and the nearby wedge surface. The densities of virtual loads can be solved by establishing equations through the continuity conditions on the interface and zero-traction conditions on free surfaces. The total wave field is obtained by the superposition of free field and scattered-wave field in elastic wedge space. Numerical results indicate that the IBEM can solve the diffraction of elastic wave in elastic wedge space accurately and effi- ciently. The wave motion feature strongly depends on the wedge angle, the angle of incidence, incident frequency, the location of lined tunnel, and material parameters. The waves interference and amplification effect around the tunnel in wedge space is more significant, causing the dynamic stress concentration factor on rigid tunnel and the displacement amplitude of flexible tunnel up to 50.0 and 17.0, respectively, more than double that of the case of half-space. Hence, considerable attention should be paid to seismic resistant or anti-explosion design of the tunnel built on a slope or hillside.展开更多
To solve seismic wave scattering by a large-scale three-dimensional(3-D) hill topography, a fast parallel indirect boundary element method(IBEM) is developed by proposing a new construction method for the wave field, ...To solve seismic wave scattering by a large-scale three-dimensional(3-D) hill topography, a fast parallel indirect boundary element method(IBEM) is developed by proposing a new construction method for the wave field, modifying the generalized minimum residual(GMRES) algorithm and constructing an Open MP plus MPI parallel model. The validations of accuracy and efficiency show that this method can solve 3-D seismic response of a large-scale hill topography for broadband waves, and overcome the weakness of large storage and low efficiency of the traditional IBEM. Based on this new algorithm architecture, taking the broadband scattering of plane SV waves by a large-scale Gaussian-shaped hill of thousands-meters height as an example, the influence of several important parameters is investigated, including the incident frequency, the incident angle and the height-width and length-width ratio of the hill. The numerical results illustrate that the amplification effect on the ground motion by a near-hemispherical hill is more significant than the narrow hill. For low-frequency waves, the scattering effect of the higher hill is more pronounced, and there is only a single peak near the top of the hill. However, for high-frequency waves, rapid spatial variation of displacement amplitude appears on the hill surface.展开更多
Because of the high importance of transportation tunnels,most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible.Recently,various numerica...Because of the high importance of transportation tunnels,most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible.Recently,various numerical methods such as finite element method(FEM),discrete element method(DEM),finite difference method(FDM)and boundary element method(BEM)have been used extremely in geosciences problems,but among these numerical methods,BEM has been used less than others because the computational algorithm is not so straightforward.This paper suggests the implementation of the indirect boundary element method(IBEM)as a formulation of BEM to analyze displacement around Shiraz-Esfahan railway tunnel in Zagros Mountains southwest of Iran.For this purpose,this tunnel has been modeled numerically using two-dimensional fictitious stress method(TWOFS)algorithm.To validate the results,they were compared with FEM results as a commonly used numerical method.Results of current theoretical study have shown that the presented approach using IBEM is reasonably accurate and can be used for analysis of displacement in geosciences problems.In rock mechanics,for problems with a low ratio of boundary surface to volume,FEM is not very well suited and may be cumbersome,but use of such a proposed IBEM approach can be particularly attractive.展开更多
The numerical method of a coupled finite element and indirect boundary element equation for computing both the structural vibration and the acoustic radiation was presented. The coupling matrices were discussed and ph...The numerical method of a coupled finite element and indirect boundary element equation for computing both the structural vibration and the acoustic radiation was presented. The coupling matrices were discussed and physical degrees of freedom of the structure were treated in terms of its modal basis in vacuum to decouple the computation from the entire coupled structural acoustic equations. The numerical results for the ellipsoidal shell immersed in two different fluids indicate that heavy fluid changes greatly structural and acoustic behavior. This method can be applied to analyze acoustic and vibration for arbitrary complex structures in fluids.展开更多
The indirect boundary element method(IBEM)is applied to investigate the scattering of elastic waves around a 3-D sedimentary basin filled with fluid-saturated poroelastic medium.Based on this method,the free field and...The indirect boundary element method(IBEM)is applied to investigate the scattering of elastic waves around a 3-D sedimentary basin filled with fluid-saturated poroelastic medium.Based on this method,the free field and scattered field can be solved according to the boundary conditions.And the numerical accuracy has been verified.The effects of parameters on elastic wave scattering are studied,such as boundary condition,incident frequency,incident angle and porosity of medium.Numerical results illustrate that the amplification effect of surface displacement near poroelastic sedimentary basin is notable.In addition,for the case of large porosity the drainage condition has a significant impact on the response amplitude.Due to the fluid exchange at the interface under the drained condition,the displacement amplitude can be much larger than that under the undrained condition in present study.The study can provide a theoretical basis for the anti-seismic design of engineering structures located in sedimentary basin.展开更多
该研究采用一种高精度间接边界元方法(indirect boundary element method, IBEM),研究了平面SV波入射下地上建筑群-地铁隧道群的动力相互作用问题。研究表明:“建筑群-隧道群”系统存在显著的动力相互作用,其规律与入射波性质、建筑物...该研究采用一种高精度间接边界元方法(indirect boundary element method, IBEM),研究了平面SV波入射下地上建筑群-地铁隧道群的动力相互作用问题。研究表明:“建筑群-隧道群”系统存在显著的动力相互作用,其规律与入射波性质、建筑物和隧道数量排布等因素密切相关。通过对比不同建筑物数量对隧道动力响应的影响,能够发现:低频波作用下,建筑物对下穿隧道的动力响应有放大作用,而高频波作用下则会削弱隧道的动力响应,最多可以降低37.5%左右。从频域分析中可以看出:隧道对地震波有较强的屏蔽作用,从而降低了其上建筑群的地震响应。建筑群的存在降低了各个单体建筑的动力响应,但在高频波作用时位于建筑群来波一侧的建筑会产生较大的动力响应。该研究成果可为城市建筑群-地铁隧道群的动力相互作用分析以及地上建筑和地铁隧道的抗震设计提供理论依据。展开更多
文摘Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress and displacement, after that, a boundary value problem with unified model was formed and solved. Ultimately, an applied numerical simulation system was developed. It was compared with the model having analytical solution for verifying the applicability and the calculating precision.
基金National Natural Science Foundation of China under Grants (51278327)the Tianjin Research Program of Application Foundation and Advanced Technology (14JCYBJC21900)
文摘The indirect boundary element method （IBEM） is developed to solve the scattering of plane SH-waves by a lined tunnel in elastic wedge space. According to the theory of single-layer potential, the scattered-wave field can be constructed by applying virtual uniform loads on the surface of lined tunnel and the nearby wedge surface. The densities of virtual loads can be solved by establishing equations through the continuity conditions on the interface and zero-traction conditions on free surfaces. The total wave field is obtained by the superposition of free field and scattered-wave field in elastic wedge space. Numerical results indicate that the IBEM can solve the diffraction of elastic wave in elastic wedge space accurately and effi- ciently. The wave motion feature strongly depends on the wedge angle, the angle of incidence, incident frequency, the location of lined tunnel, and material parameters. The waves interference and amplification effect around the tunnel in wedge space is more significant, causing the dynamic stress concentration factor on rigid tunnel and the displacement amplitude of flexible tunnel up to 50.0 and 17.0, respectively, more than double that of the case of half-space. Hence, considerable attention should be paid to seismic resistant or anti-explosion design of the tunnel built on a slope or hillside.
基金National Natural Science Foundation of China under Grant No. 51678390National Natural Science Foundation of China under Grant No. 51708391the Major Science and Technology Projects in Tianjin under Grant No. 18ZXAQSF00110。
文摘To solve seismic wave scattering by a large-scale three-dimensional(3-D) hill topography, a fast parallel indirect boundary element method(IBEM) is developed by proposing a new construction method for the wave field, modifying the generalized minimum residual(GMRES) algorithm and constructing an Open MP plus MPI parallel model. The validations of accuracy and efficiency show that this method can solve 3-D seismic response of a large-scale hill topography for broadband waves, and overcome the weakness of large storage and low efficiency of the traditional IBEM. Based on this new algorithm architecture, taking the broadband scattering of plane SV waves by a large-scale Gaussian-shaped hill of thousands-meters height as an example, the influence of several important parameters is investigated, including the incident frequency, the incident angle and the height-width and length-width ratio of the hill. The numerical results illustrate that the amplification effect on the ground motion by a near-hemispherical hill is more significant than the narrow hill. For low-frequency waves, the scattering effect of the higher hill is more pronounced, and there is only a single peak near the top of the hill. However, for high-frequency waves, rapid spatial variation of displacement amplitude appears on the hill surface.
文摘Because of the high importance of transportation tunnels,most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible.Recently,various numerical methods such as finite element method(FEM),discrete element method(DEM),finite difference method(FDM)and boundary element method(BEM)have been used extremely in geosciences problems,but among these numerical methods,BEM has been used less than others because the computational algorithm is not so straightforward.This paper suggests the implementation of the indirect boundary element method(IBEM)as a formulation of BEM to analyze displacement around Shiraz-Esfahan railway tunnel in Zagros Mountains southwest of Iran.For this purpose,this tunnel has been modeled numerically using two-dimensional fictitious stress method(TWOFS)algorithm.To validate the results,they were compared with FEM results as a commonly used numerical method.Results of current theoretical study have shown that the presented approach using IBEM is reasonably accurate and can be used for analysis of displacement in geosciences problems.In rock mechanics,for problems with a low ratio of boundary surface to volume,FEM is not very well suited and may be cumbersome,but use of such a proposed IBEM approach can be particularly attractive.
文摘The numerical method of a coupled finite element and indirect boundary element equation for computing both the structural vibration and the acoustic radiation was presented. The coupling matrices were discussed and physical degrees of freedom of the structure were treated in terms of its modal basis in vacuum to decouple the computation from the entire coupled structural acoustic equations. The numerical results for the ellipsoidal shell immersed in two different fluids indicate that heavy fluid changes greatly structural and acoustic behavior. This method can be applied to analyze acoustic and vibration for arbitrary complex structures in fluids.
基金National Natural Science Foundation of China(No.51878434)Tianjin Key Research Program of Application Foundation Advanced Technology(No.18JCZDJC39200)Tianjin City Science and Technology Support Program(No.17YFZCSF01140).
文摘The indirect boundary element method(IBEM)is applied to investigate the scattering of elastic waves around a 3-D sedimentary basin filled with fluid-saturated poroelastic medium.Based on this method,the free field and scattered field can be solved according to the boundary conditions.And the numerical accuracy has been verified.The effects of parameters on elastic wave scattering are studied,such as boundary condition,incident frequency,incident angle and porosity of medium.Numerical results illustrate that the amplification effect of surface displacement near poroelastic sedimentary basin is notable.In addition,for the case of large porosity the drainage condition has a significant impact on the response amplitude.Due to the fluid exchange at the interface under the drained condition,the displacement amplitude can be much larger than that under the undrained condition in present study.The study can provide a theoretical basis for the anti-seismic design of engineering structures located in sedimentary basin.
文摘该研究采用一种高精度间接边界元方法(indirect boundary element method, IBEM),研究了平面SV波入射下地上建筑群-地铁隧道群的动力相互作用问题。研究表明:“建筑群-隧道群”系统存在显著的动力相互作用,其规律与入射波性质、建筑物和隧道数量排布等因素密切相关。通过对比不同建筑物数量对隧道动力响应的影响,能够发现:低频波作用下,建筑物对下穿隧道的动力响应有放大作用,而高频波作用下则会削弱隧道的动力响应,最多可以降低37.5%左右。从频域分析中可以看出:隧道对地震波有较强的屏蔽作用,从而降低了其上建筑群的地震响应。建筑群的存在降低了各个单体建筑的动力响应,但在高频波作用时位于建筑群来波一侧的建筑会产生较大的动力响应。该研究成果可为城市建筑群-地铁隧道群的动力相互作用分析以及地上建筑和地铁隧道的抗震设计提供理论依据。
