INVERSE DDA OF A SYSTEM OF BLOCKS IN SPHERE COORDINATES     

Wu Yun  Wang Hui  Zhou Shuoyu  Shi Shunying 《大地测量与地球动力学》2003,23(Z1)

1　IntroductionDiscontinuousDeformationAnalysis(DDA)developedbyShiin 1 980’s[1 ,2 ] maybeusedtocalculatethedeformationanddisplacementsinamulti blocksystemandtoanalyzetherelationbe tweenforcesanddisplacementsinthesystem .Ifthesurveydisplacementofeverypointordirectionisknown,alldisplacementsanddeformationsofblocks,eventheglide ,theclosureandthestretchoftheboundary planeofblocks ,canbecalculated .TheresultisoptimallyfittedaccordingtotheLeastSquarePrinciple.DDAismainlyusedinrockblockssystems…  相似文献   

Analysis of seabed instability using element free Galerkin method     

J.G. Wang  M.R. Karim  P.Z. Lin 《Ocean Engineering》2007,34(2):247-260

Wave-induced seabed instability, either momentary liquefaction or shear failure, is an important topic in ocean and coastal engineering. Many factors, such as seabed properties and wave parameters, affect the seabed instability. A non-dimensional parameter is proposed in this paper to evaluate the occurrence of momentary liquefaction. This parameter includes the properties of the soil and the wave. The determination of the wave-induced liquefaction depth is also suggested based on this non-dimensional parameter. As an example, a two-dimensional seabed with finite thickness is numerically treated with the EFGM meshless method developed early for wave-induced seabed responses. Parametric study is carried out to investigate the effect of wavelength, compressibility of pore fluid, permeability and stiffness of porous media, and variable stiffness with depth on the seabed response with three criteria for liquefaction. It is found that this non-dimensional parameter is a good index for identifying the momentary liquefaction qualitatively, and the criterion of liquefaction with seepage force can be used to predict the deepest liquefaction depth.  相似文献   

Estimation of Land Subsidence Based on Groundwater Flow Model   总被引：8，自引：0，他引：8  

Shui-Long Shen  Ye-Shuang Xu  Zhen-Shun Hong 《Marine Georesources & Geotechnology》2006,24(2):149-167

This article presents an approach for estimating land subsidence due to withdrawal of groundwater. The proposed method calculates the groundwater seepage in 3-D-condition and calculates the land subsidence one-dimensionally. The governing equation on groundwater seepage is based on the three-dimensional mass conservation law and the principle of effective stress. The land subsidence calculation method is derived based on the following assumptions: (1) displacements occur only in the vertical direction, and (2) in vertical direction the total stresses do not change. The governing equation is solved by numerical method, i.e., finite element method (FEM) in spatial discretization and finite difference method (FDM) in time series discretization. In FEM Galerkin method is adopted and in FDM, lumped matrix method is employed. The proposed method is calibrated via analyzing 1-D consolidation problem and the results are compared with those from Terzaghi's one-dimensional consolidation theory and oedometer test. The proposed method is employed to analyze the consolidation of a soft layer due to withdrawal of groundwater from an aquifer under it. Moreover, this method is also applied to a field case of land subsidence due to groundwater pumping in a gas production field in Japan. The analytical results are compared with the field observed data. The results show that this approach simulates the field case well.  相似文献   

A continuous/discontinuous Galerkin framework for modeling coupled subsurface and surface water flow     

Clint Dawson 《Computational Geosciences》2008,12(4):451-472

We consider conjunctive surface-subsurface flow modeling, where surface water flow is described by the shallow water equations and ground water flow by Richards’ equation for the vadose zone. Coupling between the models is based on the continuity of flux and water pressure. Numerical approximation of the coupled model using the framework of discontinuous Galerkin (DG) methods is formulated. In the subsurface, the local discontinuous Galerkin (LDG) method is used to approximate ground water velocity and hydraulic head; a DG method is also used to approximate surface water velocity and elevation. This approach allows for a weak coupling of the models and the use of different approximating spaces and/or meshes within each regime. A simplified LDG method based on continuous approximations to water head is also described. Numerical results that investigate physical and numerical aspects of surface–subsurface flow modeling are presented. This work was supported by National Science Foundation grant DMS-0411413.  相似文献   

A coupling of mixed and discontinuous Galerkin finite-element methods for poroelasticity     

Phillip Joseph Phillips  Mary F. Wheeler 《Computational Geosciences》2008,12(4):417-435

In this paper, we formulate a finite-element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. We approximate the flow variables by a mixed finite-element space and the displacement by a family of discontinuous Galerkin methods. Theoretical convergence error estimates are derived and, in particular, are shown to be independent of the constrained specific storage coefficient, c _o . This suggests that our proposed algorithm is a potentially effective way to combat locking, or the nonphysical pressure oscillations, which sometimes arise in numerical algorithms for poroelasticity.  相似文献   

1966年以来华北地区一系列七级大震破裂过程的数值模拟   总被引：9，自引：5，他引：9       下载免费PDF全文

陈祖安  白武明  林邦慧  王新华  许国凯  张瑞清  黄为清 《地球物理学报》2003,46(3):373-381

用非连续变形分析方法(DDA+FEM)数值模拟，在华北地区各地块相互制约的块体系统环境中，地块边界断层上发生1966年邢台地震、 1969年渤海地震、 1975年海城地震、 1976年唐山地震等不同类型破裂模式大震的破裂过程. 数值模拟结果给出每个大震释放的主应力场，最大剪应力变化等值线图，地震前后位移变化矢量图，发震断层滑移随时间变化以及走滑错距和应力降等震源参数. 这些结果与地震的震源机制，用地震波资料研究得到的震源参数,宏观等震线,地表观测的水平位移矢量图基本一致. 其中1969年渤海地震正交破裂模式的结果与宏观等震线及小震分布图像更接近. 1976年唐山地震复杂震源模式与该震早期余震分布图像更相符. 表明用DDA+FEM方法进行数值模拟研究，能较好地模拟地震破裂过程.  相似文献   

The Present Space-Time Motion and Deformation Features of the Northeastern Margin of the Qinghai-Xizang（Tibet） Block and Its Adjacent Area     

Zhang Xiaoliang 《中国地震研究》2004,18(2):161-170

On the basis of Discontinuous Deformation Analysis (DDA), and considering the moderate intrusion of specific block boundaries to different extents, the first-order block motion model is established for the northeastern margin of Qinghai-Xizang(Tibet) block and the kinematical model for depicting deformation of small regions as well by using GPS observations of three periods (1991, 1999 and 2001). By simulating, we obtained the motion features of the firstorder blocks between the large WWN faults on the sides of the studied region, the distribution features of the principal strain rate field and the inhomogeneous motion features with spacetime of the faults in the northern boundary of the Qinghai-Xizang (Tibet) block.  相似文献   

Nuclear Waste Disposal Simulations: Couplex Test Cases     

H. Hoteit  Ph. Ackerer  R. Mosé 《Computational Geosciences》2004,8(2):99-124

We give some results obtained for the Couplex test cases proposed by the ANDRA. In this paper our aim is twofold. Firstly, to compute the release of nuclides out of the repository by concentrating on the 3D near field (Couplex 2). The simulation of the transport phenomena takes into account the dissolution of the glass containers and congruent emissions of the radio-nuclides including filiation chains and some simplified chemistry. Secondly, it is to use the near field computations in order to simulate the nuclide migrations in a 2D far field (Couplex 3). Coupling in between the two simulations takes into consideration the periodicity of the disposal modules and the geometry of the repository described in Couplex 1. The mixed finite element and discontinuous Galerkin methods are used to solve the convection–diffusion equations. In order to handle the nonlinear precipitation/dissolution term, we developed a new iterative technique that combines Picard and Newton–Raphson methods.  相似文献   

Applying disk-based discontinuous deformation analysis (DDA) to simulate Donghekou landslide triggered by the Wenchuan earthquake   总被引：1，自引：0，他引：1  

S. Amir Reza Beyabanaki  Amvrossios C. Bagtzoglou  Lanbo Liu 《Geomechanics and Geoengineering》2016,11(3):177-188

In this paper, for the first time, disk-based discontinuous deformation analysis (DDA) is applied to simulate a real landslide triggered by an earthquake. For this purpose, the kinematic behaviour of the Donghekou landslide triggered by the Wenchuan earthquake is simulated and the results obtained using disk-based DDA are compared with actual data. The comparisons show that there is a good agreement between the results obtained using disk-based DDA and observed data. The simulation results provided an understanding of the failure behaviour and temporal evolution of the landslide. This study shows that disk-based DDA is a practical numerical tool that can be used to simulate the post-failure behaviour of landslides triggered by an earthquake.  相似文献   

Development of Prebored Screw Pile Method and Evaluation of Its Bearing Characteristics     

Chung-Won Lee  Sung-Yong Park 《Marine Georesources & Geotechnology》2016,34(1):42-56

The pile-driving method produces considerable noise and vibrations. Hence, an auger-drilled pile method was developed as a low-noise and -vibration substitute. However, this method does not guarantee the bearing capacity of the pile unless some amount of pile-driving is performed. Therefore, the noise and vibration problems cannot be completely solved. In this study, a prebored screw pile method is proposed to solve these problems. In this method, piles are constructed by the rotary penetration of a screw pile into a prebored hole filled with some cement milk and whose diameter is smaller than that of the screw pile. To determine the shape of the screw pile, laboratory tests with model screw piles were conducted. Also, field load tests were conducted on an actual screw pile fabricated based on the laboratory test result and on a smooth-surfaced pile. In addition, the behavior of the screw pile was estimated by using three-dimensional finite element analysis. The results of the field load test and the numerical simulation showed that the ultimate bearing capacity and the unit skin friction of the screw pile are very superior to those of the smooth-surfaced pile and the cement milk is an important factor in the prebored screw pile method.  相似文献