流变性软土蠕变特性研究进展

针对软土的应力-应变-时间响应,从蠕变经验公式、流变元件模型以及弹粘塑性模型理论三个方面总结了流变性软土蠕变特性研究历史和最新进展.     

岩石边坡开挖及加固分析的弹粘塑性块体元方法

首先介绍了可用于边坡开挖及加固分析的弹粘塑性块体方法。该法把岩体视为具有弹粘塑性性质的结构面切割形成的刚性块体系统，考虑加固结构件在结构面上变形的协调条件，建立求解块体系统和加固构件系统的变形和破坏过程。然后介绍该方法小湾高洪坝坝肩和坝基开挖施工期稳定性研究中的应用情况。     

Rheological analysis of ceramic pastes

This paper is concerned with a number of means of characterising the rheological properties of a ceramic paste. The intrinsic flow behaviour of the paste, during upsetting, is studied experimentally by using multi coloured paste samples, as well as by a finite element numerical computation. The flow behaviour of the paste is approximated by an elasto-viscoplastic material constitutive model and implemented by using an established finite element code. The material flow properties, which are necessary for the implementation of the numerical model, were obtained using the squeeze film and hardness indentation test configurations. The flow fields generated by the simulation are shown to be a good accord with the experimental observations. The experimental procedure for selecting the material parameters which are necessary for the implementation of the numerical model is described. The accuracy of the numerical method described is also evaluated by comparing the simulation results with experimental data obtained from the net upsetting force against the imposed relative displacement behaviour and the flow visualisation of deformed coloured layers. In these respects, a comparison of the finite element model predictions and the experimental results demonstrates a good mutual agreement.     

A RHEOMETER FOR MEASURING THE PROPERTIES OF GRANULAR MATERIALS

ABSTRACT

A great many technological applications such as pneumatic handling of grains and minerals, drying of particles, gasification of solid fuels, require an understanding of the properties of granular solids. Material parameters which can describe the common phenomena exhibited by these granular materials, such as dilatancy, cohesion, adhesion, frictional resistance, etc. need to be incorporated in the model and methods devised for measuring and quantifying them. Reliable experiments are required to measure the properties of these materials. However, this branch of rheology has not been as well studied as the rheology of fluids due to the difficulties inherent to grannular materials in that they exhibit both solid-like and fluid-like properties. Here, we discuss the development of an instrument which can evaluate the material properties of grannular solids. Experimental investigations verify the commonly exhibited phenomena by these materials and estimate the various forces which are generated due to the flow of these materials, thereby enabling their characterization.     

Elasto-viscoplastic consistent tangent operator concept-based implicit boundary element methods

An elasto-viscoplastic consistent tangent operator (CTO) concept-based implicit algorithm for nonlinear boundary element methods is presented. Both kinematic and isotropic strain hardening are considered. The elasto-viscoplastic radial return algorithm (RRA) and the elasto-viscoplastic CTO and its related scheme are developed. In addition, the limit cases (e.g. elastoplastic problem) of vis-coplastic RRA and CTO are discussed. Finally, numerical examples, which are compared with the latest FEM results of Ibrahimbegovic et al. and ABAQUS results, are provided.     

龙滩水电站9号机进水口边坡反馈分析

以龙滩水电站9号机进水口边坡为例,针对高边坡施工期的工程特点,模拟施工进程以及各种施工措施,以弹-粘塑性有限单元方法为基础,利用人工智能方法建立了力学参数的联合位移反分析模型,反演了进水口边坡岩体的综合力学参数,在此基础上进行了边坡变形及稳定性的实时跟踪预报,为工程设计优化和信息化施工提供了重要的参考依据.     

库-坝耦合振动的弹粘塑性p型自适应有限元法

库-坝的耦合振动研究一直是大坝抗震分析的重要内容,也是工程设计的重要依据。采用p型自适应有限元法,建立了三维弹粘塑性模型,提出了适合p型有限单元法的误差估计方法,实现了动力响应分析的自适应升阶过程。计算结果表明:p型有限元法不仅前处理少,而且具有计算精度高和收敛速度快的优点,对求解库水-坝体的耦合振动问题是可行的和高效的;考虑耦合作用后,结构的安全系数将有所降低。     

Rate-Dependent Elasto-Viscoplastic Constitutive Model for Industrial Powders. Part 2: Model Evaluation

The PSU-EVP model's constitutive parameters for alumina powder are presented. The PSU-EVP model was also used to back-predict the triaxial test data obtained for MZF and alumina powders using constitutive parameters such as the initial voids ratio (e₀), compression index (λ), and spring-back index (κ). In the case of MZF powder, 8 out of 12 back-prediction cases had average relative difference (ARD) values below 20%. In the case of alumina powder, 7 out of 11 back-prediction cases had ARD values below 20%. Based on the back-prediction results, it was concluded that the PSU-EVP model gave fairly good results for most triaxial test data collected at 0.62 MPa/minute and 6.21 MPa/minute. However, the back-prediction results obtained at 20.7 MPa/minute had high ARD values. A sensitivity analysis was done to study the effect of changes in parameter values on the hydrostatic triaxial compression (HTC) and conventional triaxial compression (CTC) back-prediction results. From the sensitivity analysis,±10% (standard deviation variation from ±0.8σ to ±2.3σ) changes in λ and e₀ mean values had marked effect on the HTC results. However, changes in the λ, κ, and e₀ mean values do not produce any noticeable effect on the CTC prediction results. Overall, the PSU-EVP model can be considered to be the first step towards the development of a more robust and accurate model for prediction of stresses and strains in a dry powder compression process.     

不连续岩体的三维弹粘塑性复合单元模型研究

阐述了复合单元法的原理，并在此基础上提出了针对不连续岩体的算法。该算法最突出的特点是每个复合单元可以含有几个不连续面，如断层或节理。该算法的主要优点是可以方便地整合到传统有限元分析程序中，且当结构中含有较多需在计算中离散处理的不连续面时，计算网格的生成不受不连续面的数量、位置和方向的影响。算例表明这种新方法是合理和有效的。     

多层结构模型在节理岩体力学分析中的应用

运用多层结构模型来分析节理岩体的力学特征,在简要介绍多层结构模型弹粘塑性理论的基础上,制定了反映多层结构模型特点的非线性算法,编制了相应的有限元程序。程序中考虑了节理岩体一般均沿节理面受拉开裂或剪切滑移的定向破坏特点,能够反映节理岩体各向异性以及主应力旋转所导致的塑性变形。最后,给出了相应的算例,并运用该模型分析了含有两组节理的岩质边坡的变形及破坏特征。