A multiscale finite element formulation for axisymmetric elastoplasticity with volumetric locking

Similar to plane strain, axisymmetric stress problem is also highly kinematics constrained. Standard displacement‐based finite element exhibits volumetric locking issue in simulating nearly/fully incompressible material or isochoric plasticity under axisymmetric loading conditions, which severely underestimates the deformation and overestimates the bearing capacity for structural/geotechnical engineering problems. The aim of this paper is to apply variational multiscale method to produce a stabilized mixed displacement–pressure formulation, which can effectively alleviate the volumetric locking issue for axisymmetric stress problem. Both nearly incompressible elasticity and isochoric J₂ elastoplasticity are investigated. First‐order 3‐node triangular and 4‐node quadrilateral elements are tested for locking issues. Several representative simulations are provided to demonstrate the performance of the linear elements, which include the convergence study and comparison with closed‐form solutions. A comparative study with pressure Laplacian stabilized formulation is also presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Dynamic analysis of a cylindrical casing–cement structure in a poroelastic stratum

The transient response of a cylindrical casing–cement structure in a poroelastic stratum under dynamic radial tractions is one of the significant issues during the analysis of downhole operations and the selection of safe material. Based on the Biot theory and general elastic mechanics, this paper gives a set of exact solutions for radial displacement, stresses for the casing–cement system and the pore pressure of the infinite surrounding poroelastic stratum in the Laplace transform space. Solutions are presented for three different types of transient radial loadings acting on the surface of casing, i.e., suddenly applied constant load, gradually applied step load and triangular pulse load. Time domain solutions are obtained using a reliable numerical method of inverse Laplace transforms. A detailed parametric study about the transient response is presented both at the casing–cement interface and the cement–stratum interface, and the distributions of the pore pressure and the effective stresses in the stratum are also examined. Copyright © 2017 John Wiley & Sons, Ltd.     

关系逻辑与地震预报（三）

继文献1、2讨论了中长期和中短期地震预报问题之后,本文进一步运用关系逻辑探讨短临地震预报问题。基本方法是根据相交关系因子μ值识别地震活动变化型式的逐时活动状态。文中,给出了计算μ值的基本公式和各种二元逻辑关系的μ值,介绍了计算μ值的两种常用方法和在短临地震预报中的具体应用,最后,对有关四个问题作了说明。     

应用土壤水模拟模型研究区域干旱

旨在应用平原地区土壤水模拟模型，给出区域旱精分析所需的干旱信息。以多年平均土壤含水量为判断旱情发生的临界函数，经过统计分析后，提出了一种适用于平原地区分析 区域旱情严重程度的实用方法和拟定评价旱情的定量标准。     

内蒙古东乌珠穆沁旗至辽宁东沟地学断面综合地球物理特征

综合地球物理探测与研究是地学断面的重要内容和基本依据,本断面的综合地球物理研究表明:这里的地壳可分为上、中、下三层,在某些部位中层地壳可进一步分为两层,其上层在断面东南端的辽河断陷东侧及燕山台褶带的义县、朝阳地区呈现为低速层;地壳厚度在断面东南端薄,为31—35km,而在西北端厚,达38—40km;辽河裂谷东侧存在壳内高导层,整个断面上地幔高导层发育,在辽河断陷及朝阳、义县地区反映为上地幔隆起区,在西拉木伦河一带出现落差达50km左右的台阶;确认析木断裂、郯—庐断裂北段、朝阳—北票断裂、赤峰—开原断裂和西拉木伦河等断裂为壳幔深断裂;发现海城地区、朝阳—北票地区及西拉木伦河地区为地壳与上地幔结构异常区,这里也正是地震较活跃的地区。     

SETTLING PROPERTIES OF COHESIVE AND NON-COHESIVE PARTICULATE MIXTURES IN WATER

1. INTRODUCTIONAs a wide range of size distirbution including usually a certain POrtion of cohesive material is thecommon feature of the sediment constituting hyperconcentrated flows. it is desirable to study the settling properties of mixtures of cohesive and non--cohesjve sediment particles at high concentrations.Past studies on the settling of discrete particles in a suspension of fine cohesjve sediment is scarcein the literature. The Sediment Research Laboratory of Tsinghua Universi…     

太白山古冰川地貌与地质构造

太白山分布有更新世冰川地形,其冰川槽谷在平面上呈“十”字型排列;横剖面EW向的呈宽谷形,NS向是呈U型:纵剖面EW向比较平坦,SN向呈阶梯状,其中有许多断裂陡坎。冰斗均位于断裂交汇点,面积不大而深度却相当大。这些地形的形态特征可以用构造加以解释,断裂破碎带是最有利于冰川刨蚀的地段。     

快速序贯算法

本文讨论了序贯算法的基本原理，与ｋａｌｍａｎ滤波的关系，和序贯算法的渐近性态，得到无先验信息的序贯算法不受初值的影响。实例分析表明，此序贯算法可适于方程系数阵的求逆、求解和病态方程的快速解算。     

华南二叠-三叠系的成因地层序列及古特提斯海重建

总结各类沉积盆地的沉积和地层格架，厘定出６类等时性地层界面和５个级别的成因地层单位，在分析地层界面性质和各类成因地层单位沉积构成的基础上，将华南二叠－三叠系划分为７个沉积幕、３个构造沉积幕和２个沉积盆地域、恢复了华南板块二叠－三叠纪的演化过程，论述了板块构造运动，海平面升降和源区侵蚀作用对各级成因地层单位的控制意义，证明了华南的古特提斯海经历了陆表海和伸展裂谷海两个演化阶段。