Stress and Displacement Distribution of Soft Clay Slope with 2D and 3D Elastoplastic Finite Element Method

Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.     

Very Low Bit Rate Video Coding Using Motion Compensated 3 D Wavelet TransformVery Low Bit Rate Video Coding Using Motion Compensated 3 D Wavelet Transform

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3D thermoelasticity solutions for functionally graded thick plates

Thermal-mechanical behavior of functionally graded thick plates, with one pair of opposite edges simply supported, is investigated based on 3D thermoelasticity. As for the arbitrary boundary conditions, a semi-analytical solution is presented via a hybrid approach combining the state space method and the technique of differential quadrature. The temperature field in the plate is determined according to the steady-state 3D thermal conduction. The Mori-Tanaka method with a power-law volume fraction profile is used to predict the effective material properties including the bulk and shear moduli, while the effective coefficient of thermal expansion and the thermal conductivity are estimated using other micromechanics-based models. To facilitate the implementation of state space analysis through the thickness direction, the approximate laminate model is employed to reduce the inhomogeneous plate into a homogeneous laminate that delivers a state equation with constant coefficients. The present solutions are validated by comparisons with the exact ones for both thin and thick plates. Effects of gradient indices, volume fraction of ceramics, and boundary conditions on the thermomechanical behavior of functionally graded plates are discussed.     

The limit analysis in soil and rock： a mature discipline of geomechanics

The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the factor of safety. It has been successfully extended to the area of active earth pressure analysis that accounts for different input of locations of earth pressure applications. Those methods that employ slices with inclined interfaces give an upper-bound approach to the stability analysis. It enjoys a sound mechanical background and is able to provide accurate solutions of soil plasticity. It has been successfully extended to the area of bearing capacity analysis in which various empirical coefficients are no longer necessary. The 3D upper- and lower-bound methods under this framework have been made possible and show great potential for solving various engineering problems.     

Construction of an ultra-deep diaphragm wall: a case study

This paper presents a case study on an ultra-deep diaphragm wall with a depth of 110 m constructed in Ningbo City. The in-situ application shows that using Bauer BC40 cutter machine in conjunction with cutter wheels specified for different strata would be qualified for constructing the 110 m diaphragm wall with high efficiency and precision given that the quality of slurry and poured concrete can be guaranteed. The ground settlement can be effectively controlled by using the overlapping construction method. Sliding failure as a whole characterized by pronounced lateral deformation is likely to occur in the upper muddy clay layer due to its high compressibility and sensitivity. In contrast, local collapse of trench walls tends to happen in the sandy silt strata. Furthermore, careful attention should be paid to sandy silt during the entire construction period as the vertical displacement of the sandy silt continues to develop even after concrete pouring     

概率极限状态设计法在确定地基承载力中的应用

传统的安全系数法确定地基承载力存在许多缺陷。本文对安全系数法存在的问题进行了详细的分析。介绍了概率极限状态设计法在确定地基承载力中的应用，可供工程实践之参考。     

Automatic generation method of geological cross-sections in dredging engineering based on 3D solid NURBS models

An automatic generation method of geological cross-sections in dredging engineering based on 3D geological solid models is presented.The 3D geological models are built applying the non-uniform rational B-splines(NURBS) technique,and a 2D profile can be calculated and generated automatically through Boolean operation to meet the demands of dredging projects.Moreover,an automatic marking method for geological attributes is put forward based on database technology,and the geological attributes include the profile name,scale,horizontal and vertical relative coordinates,geological lithology,and 2D standard lithology legend.At the same time,the automatic marking method can also provide an interactive mode for geological engineers to edit and modify the profile in the modeling system.Practical engineering applications show that the automatic generation method is a simple,flexible,fast and precise visual graphics rendering process that can create 2D standard profiles automatically and efficiently.This method also provides a convenient support tool for geological engineering digital analysis.     

Effects of overburden, rock strength and pillar width on the safety of a three-parallel-hole tunnel

During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width as variables, a series of 3D numerical analysis was carried out to examine the effect of each variable on the safety of the tunnel, in particular the rock pillar. A stress strength ratio （SSR） was used to define whether the safety of the rock pillar was exceeded. A simple design chart for the case of three-parallel-hole tunnel, which took into account the influence of overburden depth, rock pillar width, and rock strength, was also proposed for used in the preliminary design stage.     

Generalization of 3D Mandelbrot and Julia sets

INTRODUCTION Mandelbrot and Julia sets have been extensively investigated in great detail in terms of their aestheti-cally pleasing geometrical shapes, infinite detail, self-similarity, periodicity and many other character-istics. The beauty and intricacy of these sets in the complex plane stimulate the scholars’ enthusiasm for viewing sets that occupy more than two dimensions. However, investigations on the generalizations of fractal sets to higher-dimensional spatial space have come u…     

基于Cesium的机场净空保护区三维可视化管理关键技术

针对机场净空管理中存在的可视化差、精细管理不足等问题,基于三维Cesium引擎研究机场净空保护区三维信息显示与管理等关键技术。首先,依据规范要求计算障碍物限制面的三维关键点,运用Cesium构建障碍物限制面及预警阈值面的三维模型;然后,通过分层分块组织、线性四叉树索引构建,基于优先等级的数据加载优化实现海量三维数据的调度;最后,以天津机场为例建立管理系统。运行效果表明:该系统可有效提升净空安全管理的数字化水平,为机场高效运行提供了有力保障。     

Reliability analysis of diesel engine crankshaft based on 2D stress strength interference model

INTRODUCTION For critical structures and applications, requiring a given reliability, it is necessary to account for un-certainties and variability in material properties, loads and geometric tolerances. Using various reliability analysis methods, we can determine the reliability of existing structures or systems; or design new structures or systems with certain desired reliability. Manufacturing processes may involve many factors that have inherent uncertainties or random variations in th…     

钢筋混凝土简支梁跨高比的上下限分析

对钢筋混凝土简支梁的跨高比与其承载力、刚度和裂缝宽度的关系进行分析,说明按经验的跨高比选择梁的截面尺寸不尽合理。通过计算得出梁的跨高比有上下限的结论。     

Analysis of 1D consolidation with non-Darcian flow described by exponent and threshold gradient

Numerous experiments have shown that the water flow in fine-grained soils can obey an exponential relationship at small gradients and a linear relationship when the hydraulic gradient exceeds a certain limit. Based on the non-Darcian flow described by exponent and threshold gradient, the theory of 1D consolidation is modified in this paper to consider a linear variation in the vertical total stress with depth and the effect of ramp loading. The numerical solutions were derived in detail by the finite difference method for excess pore water pressure and the average degree of consolidation. Finally, the influence of various parameters on consolidation behavior was investigated. The results show that the rate of consolidation is reduced when non-Darcian flow described by exponent and threshold gradient is adopted in the theory of 1D consolidation. As well the distribution of vertical total stress has a great influence on the dissipation of excess pore water pressure, either for pervious top and pervious bottom （PTPB） or for pervious top and impervious bottom （PTIB）. For the case of PTIB, the distribution of vertical total stress in a foundation has a great influence on the rate of consolidation; however, for the case of PTPB, the rate of consolidation is independent of the distribution of vertical total stress. The rate of consolidation is dependent on the ratio of the thickness of a soil layer to the equivalent head of the final average vertical total stress; the greater the value of this ratio, the slower the rate of consolidation. Finally, an increase in construction time reduces the consolidation rate of a foundation. Thus, consolidation behavior of 1D consolidation with non-Darcian flow has been thoroughly acquainted in this paper.     

3D identification and stability analysis of key surface blocks of rock slope

Complicated geological structures make it difficult to analyze the stability of rock slopes, such as faults, weak intercalated layers or joint fissures. Based on 3D geological modeling and surface block identifying methods, an integrated methodology framework was proposed and realized to analyze the stability of surface blocks in rock slopes. The surface blocks cut by geological structures, fissures or free faces could be identified subjected to the four principles of closure, completeness, uniqueness and validity. The factor of safety(FOS)of single key block was calculated by the limit equilibrium method. If there were two or more connected blocks, they were defined as a block-group. The FOS of a block-group was computed by the Sarma method. The proposed approach was applied to an actual rock slope of a hydropower project, and some possible instable blocks were demonstrated and analyzed visually. The obtained results on the key blocks or block-groups provide essential information for determining potential instable region of rock slopes and designing effective support scheme in advance.     

Plastic limit load analysis for pressure pipe with incomplete welding defects based on the extended Net Section Collapse Criteria

With von Mises yield criterion, the loading range of Net Section Collapse （NSC） Criteria is extended from combined tension and bending loadings to combined bending, torsion and internal pressure loadings. A new theoretical analyzing method of plastic limit load for pressure pipe with incomplete welding defects based on the extended NSC Criteria is presented and the correlative formulas are deduced, the influences of pipe curvature, circumferential length and depth of incomplete welding defects on the plastic limit load of pressure pipe are considered as well in this method. Meanwhile, according to the orthogonal experimental design method, the plastic limit loads are calculated by the finite element method and compared with the theoretical values. The results show that the expressions of plastic limit load of pressure pipe with incomplete welding defects under bending, torsion and internal pressure based on extended NSC criteria are reliable. The study provides an important theoretical basis for the establishment of safety assessment measure towards pressure pipe with incomplete welding defects.     

微弧氧化法制备镁合金陶瓷膜的研究

采用双极性脉冲电源对置于Na2Al2O4溶液中的AZ91D镁合金进行微弧氧化处理，研究了溶液配方和电源参数（包括电压、频率、占空比等）对微弧氧化膜的组成与结构的影响。结果表明：不同的电参数作用下形成的氧化膜的结构是相似的，膜层由内层致密层和外层疏松层组成，其主要物相组成是Mgo和MgAl2O4；不同电参数对膜层的厚度的影响各不相同，随着电压和占空比的增大，膜层增厚速度将加大，而频率的影响则与之相反。     

3D displacement measurement by white light digital image analysis in frequency domination area

In this paper, white light digital image analysis in frequency domination area for measuring 3D displacement is put forward. The measuring system has the characteristics of wholefield, non-contact and omnibearing measurement. It is simple and the coherent light is not demanded. Gray images before and after deformation are recorded using two CCDs at two different shooting angles, then digitalized and analyzed by frequency domination correlation arithmetic. The 2D displacement obtained is used to formulate 3D displacement via mathematical transformation, The experimental plate is 40 mm in length, 30 mm in width and 10 mm in height. The definite displacement is given using a 3D precise adjusting frame. The 3D displacement is calculated and compared with the definite displacement. The error is 4%-11% and the availability of this method was certified. Using this method, the compression deformation of a thin-wall cylinder with 140 mm in height, 64 mm in inner diameter and 64,6 mm in external diameter, was also measured. This method is proper to measure dynamic deformation.     

Progressive failure analysis of slope with strain-softening behaviour based on strength reduction method

Based on the strength reduction method and strain-softening model,a method for progressive failure analysis of strain-softening slopes was presented in this paper.The mutation is more pronounced in strain-softening analysis,and the mutation of displacement at slope crest was taken as critical failure criterion.An engineering example was provided to demonstrate the validity of the present method.This method was applied to a cut slope in an industry site.The results are as follows:(1) The factor of safety and the critical slip surface obtained by the present method are between those by peak and residual strength.The analysis with peak strength would lead to non-conservative results,but that with residual strength tends to be overly conservative.(2) The thickness of the shear zone considering strain-softening behaviour is narrower than that with non-softening analysis.(3) The failure of slope is the process of the initiation,propagation and connection of potential failure surface.The strength parameters are mobilized to a non-uniform degree while progressive failure occurs in the slope.(4) The factor of safety increases with the increase of residual shear strain threshold and elastic modulus.The failure mode of slope changes from shallow slip to deep slip.Poisson’s ratio and dilation angle have little effect on the results.     

Technical illustration based on 3D CSG models

Non-photorealistic rendering (NPR) is effective at conveying information, more expressive or more beautiful than its photorealistic counterparts (Lans-down and Schofield, 1995). Technical illustration is a special subset of NPR since both of them share human perception as common driving force. NPR aims at rendering 3D objects to convey engineering informa-tion, and is very popular in engineering drawing. Many researchers had investigated its application for technical illustration. Gooch e…     

基于点安全系数法的边坡稳定性评价

针对目前在边坡稳定分析中,常规的数值计算方法和极限平衡法都是利用边坡的整体安全系数来表征,不能反映边坡各部位稳定性的不同,进而无法将边坡稳定性与滑动机理联系起来。本文根据建立的Ansys有限元正分析模型先计算应力场,然后求解出模型各点处的安全系数值,再利用Ansys软件的后处理功能绘制出模型的安全系数等值线云图,最后对边坡的稳定性作出综合评价。