3-D fracture network dynamic simulation based on error analysis in rock mass of dam foundation

Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network model and measured data,a 3-D fracture network dynamic modeling method based on error analysis was proposed.Firstly,errors of four fracture volume density estimation methods(proposed by ODA,KULATILAKE,MAULDON,and SONG)and that of four fracture size estimation methods(proposed by EINSTEIN,SONG and TONON)were respectively compared,and the optimal methods were determined.Additionally,error index representing the deviation between fracture network model and measured data was established with integrated use of fractal dimension and relative absolute error(RAE).On this basis,the downhill simplex method was used to build the dynamic modeling method,which takes the minimum of error index as objective function and dynamically adjusts the fracture density and size parameters to correct the error index.Finally,the 3-D fracture network model could be obtained which meets the requirements.The proposed method was applied for 3-D fractures simulation in Miao Wei hydropower project in China for feasibility verification and the error index reduced from 2.618 to 0.337.

Discrete Element with Flexible Connector for Dynamic Analysis of 3-D Beam Structures

Combined multi-body dynamics with structural dynamics, a new discrete element with flexible connector, which is applicable for 3-D beam structures, is developed in this paper. Both the generalized elastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diagonal in a general case. The zero-length rigid element is introduced to simulate the node at which multiple elements are jointed together. It may also be effective when the axes of adjacent elements are not in the same line. The examples for eigenvalue calculation show that the model is successful. It can be extended to the geometric nonlinear response analysis.

ANALYSIS OF SLAB EDGING BY A 3-D RIGID VISCO-PLASTIC FINITE ELEMENT METHOD

3-D rigid visco-plastic finite element method (FEM) is used in the analysisof metal forming processes, including strip and plate rolling, shape rolling, slab edging, specialstrip rolling. The shifted incomplete Cholesky decomposition of the stiffness matrix with thesolution of the equations for velocity increment by the conjugate gradient method is combined. Thistechnique, termed the shifted ICCG method, is then employed to solve the slab edging problem. Theperformance of this algorithm in terms of the number of iterations, friction variation, shiftedparameter psi and the results of simulation for processing parameters are analysed. Numerical testsand application of this technique verify the efficiency and stability of the shifted ICCG method inthe analysis of slab edging.

Sparse flight spotlight mode 3-D imaging of spaceborne SAR based on sparse spectrum and principal component analysis

The spaceborne synthetic aperture radar(SAR)sparse flight 3-D imaging technology through multiple observations of the cross-track direction is designed to form the cross-track equivalent aperture,and achieve the third dimensionality recognition.In this paper,combined with the actual triple star orbits,a sparse flight spaceborne SAR 3-D imaging method based on the sparse spectrum of interferometry and the principal component analysis(PCA)is presented.Firstly,interferometric processing is utilized to reach an effective sparse representation of radar images in the frequency domain.Secondly,as a method with simple principle and fast calculation,the PCA is introduced to extract the main features of the image spectrum according to its principal characteristics.Finally,the 3-D image can be obtained by inverse transformation of the reconstructed spectrum by the PCA.The simulation results of 4.84 km equivalent cross-track aperture and corresponding 1.78 m cross-track resolution verify the effective suppression of this method on high-frequency sidelobe noise introduced by sparse flight with a sparsity of 49%and random noise introduced by the receiver.Meanwhile,due to the influence of orbit distribution of the actual triple star orbits,the simulation results of the sparse flight with the 7-bit Barker code orbits are given as a comparison and reference to illuminate the significance of orbit distribution for this reconstruction results.This method has prospects for sparse flight 3-D imaging in high latitude areas for its short revisit period.

Characteristics of an Axial-flux Permanent Magnet Synchronous Machine with Contra-rotating Rotors under Unbalanced Load Condition from 3-D Finite Element Analysis

During recent years,the axial-flus PMSM with contra-rotating rotors has become a hot topic in academic research due to its high efficiency and simple structure.However,its back-EMF may be distorted under the condition of different angular positions.This paper investigates characteristics of the novel motor used for contra-propeller driving.Considering the torque ripple and current oscillation under unbalanced load condition,this paper analyzes the distorted back-EMF of the machine when its two rotors get different angular positions during rotating.The analysis results are validated by transient-magnetic 3-D FEA method,which the 3-D FEA software is used to model this motor and transient simulations are carried out to obtain its magnetic characteristic and main performances.A main focus is put on the back-EMF characteristic with different angular positions between the two rotors.Furthermore,the characteristic of torque production under unbalanced load is investigated.Finally,a prototype motor is fabricated to validate the analyses of this paper.

A TENSOR ANALYSIS METHOD FOR ESTIMATING 3-D MOTION PARAMETERS

By using the center projection image sequence to estimate 3-D motion parameters,one needs to know the corresponding relationship between the feature of motion object in spaceand the projection coordinate on image plane.In order to avoid using the relationship of featurecorrespondence,the tensor analysis method in the affine transformation system is presented,andthe simulation data of experimental results are given.

Probabilistic analysis on fault tolerance of 3-Dimensional mesh networks

The probability model is used to analyze the fault tolerance of mesh. To simplify its analysis, it is as-sumed that the failure probability of each node is independent. A 3-D mesh is partitioned into smaller submeshes,and then the probability with which each submesh satisfies the defined condition is computed. If each submesh satis-fies the condition, then the whole mesh is connected. Consequently, the probability that a 3-D mesh is connected iscomputed assuming each node has a failure probability. Mathematical methods are used to derive a relationship be-tween network node failure probability and network connectivity probability. The calculated results show that the 3-D mesh networks can remain connected with very high probability in practice. It is formally proved that when thenetwork node failure probability is boutded by 0.45 %, the 3-D mesh networks of more than three hundred thousandnodes remain connected with probability larger than 99 %. The theoretical results show that the method is a power-ful technique to calculate the lower bound of the connectivity probability of mesh networks.

3-D Numerical Simulation on the Chip Machining Process of a Metal Block

In this paper, the cutting process of a metal block is numerically simulated by the dynamic explicit FE code ABAQUS. Taking thermo-mechanical coupling effect into consideration, the simulation presents the variation of temperature, stress and strain distribution in the workpiece and chip. The effective plastic strain failure criterion is applied to modeling the chip separation and plastic formation. And the phenomenon of the contact and friction between the workpiece and the cutting tool are described in the paper.

SAR tomography imaging via higher-order spectrum analysis

To deal with the non-Caussian noise in standard 2-D SAR images, the deramped signal in imaging plane, and the possible symmetric distribution of complex noise, the fourth-order cumulant of complex process is introduced into SAR tomography. With the estimated AR parameters of ARMA model of noise through Yule-Walker equation, the signal series of height is pre-filtered. Then, through ESPRIT, the spectrum is obtained and the aperture in height direction is synthesized. Finally, the SAR tomography imaging of scene is achieved. The results of processing on signal with non-Gaussian noise demonstrate the robustness of the proposed method. The tomography imaging of the scenes shows that the higher-order spectrum analysis is feasible in the application.

Numerical and Dimensional Analysis for Prediction of Line Heating Residual Deformations

Line heating process is a very complex phenomenon as a variety of factors affects the amount of residual deformations. Numerical thermal and mechanical analysis of line heating for prediction of residual deformation is time consuming. In the present work dimensional analysis has been presented to obtain a new relationship between input parameters and resulting residual deformations during line heating process. The temperature distribution and residual deformations for 6 mm, 8 mm, 10 mm and 12 mm thick steel plates were numerically estimated and compared with experimental and published results. Extensive data generated through a validated FE model were used to find co-relationship between the input parameters and the resulting residual deformation by multiple regression analysis. The results obtained from the deformation equations developed in this work compared well with those of the FE analysis with a drop in the computation time in the order of 100 (computational time required for FE analysis is around 7 200 second to 9 000 seconds and where the time required for getting the residual deformation by developed equations is only 60 to 90 seconds).

Thermo-mechanical and Experimental Analysis of Double Pass Line Heating

The present investigation deals with process analysis of oxy-acetylene flame assisted double pass line heating for varying plate thickness, oxy-acetylene flame as the heat source for multi pass line heating to achieve 3-D bending of plates with varying thicknesses was studied. The oxy-acetylene flame was modeled as the moving heat source in the FEM analysis. The transient thermal histories were predicted taking into account the temperature dependent thermo-mechanical properties. A comparative study between single pass and double pass line heating residual deformation was also carried out. The temperature distribution and residual detbrmations predicted by the numerical model developed in the present work compared fairly well with those of the experimental ones.

Stochastic analysis of excavation-induced wall deflection and box culvert settlement considering spatial variability of soil stiffness

In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.

3-D Modelling of the Confederation Bridge Using Data of Full Scale Tests

Long-span bridges are special structures that require advanced analysis techniques to examine their performance. This paper presents a procedure developed to model the Confederation Bridge using 3-D beam elements. The model was validated using the data collected before the opening of the bridge to the public. The bridge was instrumented to conduct fullscale static and dynamic tests. The static tests were to measure the deflection of the bridge pier while the dynamic tests to measure the free vibrations of the pier due to a sudden release of the static load. Confederation Bridge is one of the longest reinforced concrete bridges in the world. It connects the province of Prince Edward Island and the province of New Brunswick in Canada. Due to its strategic location and vital role as a transportation link between these two provinces, it was designed using higher safety factors than those for typical highway bridges. After validating the present numerical model, a procedure was developed to evaluate the performance of similar bridges subjected to traffic and seismic loads. It is of interest to note that the foundation stiffness and the modulus of elasticity of the concrete have significant effects on the structural responses of the Confederation Bridge.

复杂断块构造的地应力场研究——以海拉尔盆地贝尔凹陷希3断块为例

根据贝尔凹陷希3断块的井孔崩落资料以及差应变和波速各向异性法得到的地应力测量数据,采用有限元约束优化反演法,对希3断块的三维地应力场进行了模拟,探讨了断层对地应力场的影响以及断块构造的地应力分布特征.研究结果表明:断层附近的地应力分布主要受邻近断层的影响,且与扰乱程度、断层的几何尺寸和距离断层的远近等因素相关.不同类型断层的纵向延伸加剧了纵向上地应力场分布的复杂性.这一现象在单断式断块油气藏有所体现,在双断式、三断式以及断阶式断块油气藏中表现得尤为突出;断层对应力方向的扰动作用在弹性模量高的硬地层中更为剧烈.离散"点"的实测值不能全面反映断块构造应力场全貌,三维数值模拟是断块油气藏地应力场定量分析的有效手段.

Sensitivity analysis for the total nitrogen pollution of the Danjiangkou Reservoir based on a 3-D water quality model

Inter-basin water deal of nitrogen are great transfers containing a great threats to human health, biodiversity, and air and water quality in the recipient area. Danjiangkou Reservoir, the source reservoir for China＇s South-to-North Water Diversion Middle Route Project, suffers from total nitrogen pollution and threatens the water transfer to a number of metropolises including the capital, Beijing. To locate the main source of nitrogen pollution into the reservoir, especially near the Taocha canal head, where the intake of water transfer begins, we constructed a 3-D water quality model. We then used an inflow sensitivity analysis method to analyze the sig- nificance of inflows from each tributary that may contribute to the total nitrogen pollution and affect water quality. The results indicated that the Han River was the most significant river with a sensitivity index of 0.340, followed by the Dan River with a sensitivity index of 0.089, while the Guanshan River and the Lang River were not significant, with the sensitivity indices of 0.002 and 0.001, respectively. This result implies that the concentration and amount of nitrogen inflow outweighs the geographical position of the tributary for sources of total nitrogen pollution to the Taocha canal head of the Danjiangkou Reservoir.

基于现场调查及三维非线性FEM分析的钢框架结构安全性评价研究

作为日本最古老的地铁线路,东京地铁银座线采用钢框架结构形式至今已安全运营了将近90年。通过对该隧道结构体建立的三维FEM模型,非线性分析了静载作用下结构体的应力、应变分布特性。再以对比分析模型分析与现场实际调查两方面得出的裂缝位置及裂缝应变大小,验证了分析方法的合理性与适用性;然后采用该分析方法对隧道结构体的安全性进行评价分析,分析结果显示结构目前依然具备足够的安全性能。

Numerical analysis of 3-D sound propagation in lined ducts with circumferential mode sound sources at inlet

Numerical analysis of three-dimensional sound propagation in soft-soft or soft-hard circular ducts with circumferential and axial modes of sound sources at the inlet has been carried out. In this paper , the numerical method and the samples are offered and the effects of circumferential and axial modes on numerical results are discussed in detail .

Numerical Analysis of Thermal Convections in a Three-dimensional Cavity: Influence of Difference in Approximation Models on Numerical Solutions

In order to develop the practical approximation models suitable to flow fields at low Mach number with large temperature difference, the influence of difference in approximation models on numerical solutions was investigated by solving the natural convection in the 3-D enclosures with vertical sidewalls differentially heated and the heated bottom wall using 3 approximation models, that is Boussinesq approximation, low Mach Number approximation and approximation model proposed by Mlaouah. As results of the simulation, the effects of the differences in the three approximation models on the numerical solutions become clear.

地应力场三维有限元拟合研究

本文应用三维有限元拟会方法，根据实测地应力资料，对某金矿的地应力场分布规律进行了研究。提出了结构面结点偶对分析原理和方法，用以正确模拟断层对地应力场分布的影响。分析表明，计算结果与实测值接近程度非常好，说明通过三维有限元拟合方法建立的矿区地应力场分布模型具有较高的精度。

旧混凝土路面板底脱空的有限元分析

水泥混凝土路面的破坏类型有多种 ,其中路面板底脱空是水泥混凝土路面板的主要破坏类型。利用 AL GORFEAS公司开发的 SAP 93软件 ,采用材料非线性的有限元模型 ,对路面板底脱空修补前后的受力情况进行了弹塑性分析。分析结果表明 ,修补后路面板底的应力集中现象得到了明显的改善。