Theory of one dimensional consolidation of two-layered soil with partially drained boundaries

In this paper, a fully explicit analytical solution is presented for one-dimensional consolidation of two-layered soils with partially drained boundaries. It can be shown that the available analytical solutions so far developed for one dimensional consolidation of soil are the special cases of the solution presented herein. According to the solution, some diagrams are prepared and the relevant consolidation behavior of layered soils associated with partially drained boundaries is discussed in detail. Furthermore, the applications of the solution are illustrated in an example problem.     

对中国第四系中统划分方案的回顾与讨论

国内地层规范中规定第四系划分为两个统,即全新统和更新统,后者又分为下、中、上３个阶。这３个阶大部分第四纪地质工作者习惯称为下、中、上更新统。本文仍暂用此名。下、中更新统的界线一般以Ｂ／Ｍ为界,年龄为０．７８ＭａＢ．Ｐ,但从泥河湾组、午城组顶界看,可能要到１００～１．２０ＭａＢ．Ｐ．;中、上更新统界线,一般以０．１２８ＭａＢ,Ｐ为界,代表末次冰期的开始,但从黄土高原Ｓ１底界、萨拉乌苏组底界和小渡口组顶界看,其年龄为０．１２８ＭａＢ,Ｐ,或０．１４ＭａＢ Ｐ或０．２０ＭａＢ,Ｐ．;上更新统与全新统的界线,其年龄基本上集中在０．０１０～０．０１１ＭａＢ,Ｐ,代表冰期结束,温暖期开始。     

Local transmitting boundaries for transient elastic analysis

The aim of this paper is to investigate and develop alternative methods of analyzing problems in dynamic soil–structure-interaction (SSI). The interaction means that the amplitude of structural response is effected by additional energy dissipation through radiation and material damping in the soil. The surrounding soft soil behaves as a natural damper for a massive and stiff structure supported or embedded in it. The main focus is the major difficulty posed by such an analysis — the phenomena of waves that radiate outward from the excited structures towards infinity. In numerical calculations only a finite region of the foundation medium is analyzed and something is done to prevent the outgoing radiation waves from reflecting at the boundary region.Development of a simple and efficient finite element (FE) procedure for the solution directly in the time domain of transient SSI problems is the main concern. The central feature of the procedure is local absorbing boundaries used to render the computational domain finite. These boundaries are local in both time and space and are completely defined by a pair of symmetric stiffness and damping matrices. As the effort for implementing them is the same as for the impedance boundary condition (BC) considering the angle of incidence, standard assembly procedure can be used. Due to the local nature they also preserve the overall structure of the global equations of motion. Even though the focus is in the time domain the same equations of motions can be used to determine the solution under time-harmonic excitation directly in the frequency domain. Explicit formulae for the element matrices are included in the paper and numerical examples for transient radiation model problems to illustrate the validity and accuracy of the new procedures, are given.     

Formation Mechanism of "Drag Depressions" and Irregular Boundaries in Intraplate Deformation

Almost all intraplate caprocks experienced strong deformation during the convergence of microplates, and then disintegrated into many secondary geologic units with the special characters, such as irregular boundaries and particular structural assemblages. In order to understand the formation mechanism of these special phenomena, a rheological experiment on the structural scenery of the Tongling area is carried out. The result shows that the primary regular and uniform boundaries of the Tongling area becomes irregular because of the enclosing and confinement of surrounding geological units in the process of "compression-shearing-rotation-drag"; simultaneously, two specific "drag depressions" developed at two opposite corners of the block. The former and the later phenomena can be regarded as a typical regional-scale rheological effect and necessary outcome of intraplate deformation respectively.     

昆明吴家营岩溶水系统边界的水文地球化学分析

西南岩溶水系统边界条件复杂,其中水头隔水边界在水动力条件改变的情况下具有不稳定的隔水特性。文章以昆明吴家营岩溶地下水系统为例,通过水化学组分动态序列图解法、数理统计法及水文地球化学模拟等方法对研究区边界特性进行了研究。研究结果表明该岩溶水系统水动力条件丰水季优于枯水季,并存在与边界外发生水力联系的越流通道;丰水季时岩溶槽谷区地下水在高水力梯度的驱动下向下绕过玄武岩隔水层,通过下部阳新灰岩对系统内岩溶水进行越流补给,枯水季受深部滞流阻水影响,越流补给现象不明显;由此得出此类水头边界的隔水特性会随水动力条件的改变而具有动态响应特征。研究成果对当地岩溶水资源量的评价和合理开发利用提供科学依据。      

基于光释光测年的中国黄土中氧同位素阶段2/1和3/2界限位置及年代的确定

文章简要总结了近几年来在确定黄土中氧同位素阶段2/1和3/2界线位置、年代以及与此相关的光释光测年方面的最新进展。在黄土与全球变化的研究中,更新世与全新世界线的位置及其年代的确定始终难于解决。常用的方法是用磁化率曲线来定性确定这一界线,而其年代则从别处引用。近几年来光释光测年的一些最新进展为黄土高分辨率的光释光年代序列提供了条件,基于高分辨率光释光测年的沉积速率模型较好地解决了这一难题。由于冰期时黄土沉积速率较高,而间冰期(或间冰阶)时沉积速率相对较低,沉积速率模型认为,沉积速率变化的拐点即是冰期和间冰期的界线。运用这一模型,测算得出甘肃省临夏盆地塬堡剖面氧同位素阶段2/1和3/2界线的年代分别为13.48±1.15ka和25.8±2.1ka。     

北祁连-河西地区强震地点预测

借助弹性块体边界负位错模型,获取了北祁连 河西地区1971～2000年5个时段地壳垂直运动反映的 构造块体及其边界断层运动、变形参量及构造梯度场的时空演化图像,高应变能积累部位和锁定能量强度。研究 了与门源Ms6.4、景泰Ms6.2、永登Ms5.8、景泰Ms5.9、玉门Ms5.9以及2003年10月25日民乐 山丹Ms6.1等 强震孕育有关的背景性前兆特征,初步建立了该区强震地点判定的定量依据:①在较大范围强烈隆起区内及其边 缘、梯度场高值区内及其边缘,尤其是与构造走向较为一致、隆起量5mm/a以上或梯度值8×10-8/a以上能达到 方圆50～100km甚至更大的区域;②强位错(3mm/a以上)锁定区段及其附近,较强负位错应力降或负位错地震 矩(分别为5×103Pa/a和5×1016Nm/a左右甚至更高)区段及其附近;或者显著加强段及其附近,可能发生6级左 右或6级以上地震。对应的异常越突出、项数越多、位置越重合,发震危险性越大。     

Political Organization of Space in Advanced Placement Human Geography

Abstract

The political geography section of the course offers the opportunity to introduce students to one of the most important ways in which humans have divided up the surface of the Earth for purposes of management and control. By challenging students to consider what lies behind the patterns on political maps, this segment of the course can encourage the development of a critical geographical perspective while enhancing student appreciation of the link between geography and current events.     

边界谈判划界决策支持系统的设计与应用

边界谈判划界是一个重要而又复杂问题,结合了谈判划界业务流程;探讨了在GIS空间技术支持下,谈判划界系统各功能模块设计以及系统的数据设计,实现对谈判划界数据的有效管理,提供了划界辅助工具和资源评价分析工具,为谈判划界提供了决策支持.     

辅助边界谈判划界子系统设计及关键技术

边界谈判划界是一个重要而又复杂的问题,本文结合谈判划界业务流程,探讨了在GIS空间技术支持下,谈判划界系统各功能模块设计以及系统的数据设计,实现对谈判划界数据的有效管理,提供划界辅助工具和资源评价分析工具,为谈判划界提供决策支持.