考虑吸附水的非饱和土耗散本构关系研究

为了探索土水吸附特征对非饱和土力学特性的影响,根据赋存环境把土中水分为储存在毛细管内液面张力吸纳作用占主导的自由水和包裹在土颗粒周围基质静电吸着作用占主导的吸附水。通过把土颗粒基质与吸附水一起共同视为非饱和土骨架相,自由水视为液相、土中气视为气相,获得了考虑吸附水的非饱和土功表达式。根据热力学耗散理论,利用功表达式和局部热力学平衡假定,获得非饱和土在绝热变形过程中的熵流和熵产。基于热力学吸附平衡理论获得土中吸附水的吸附方程,进而提出具有实用性的吸附水土-水特征曲线。利用熵产表达式中的热力学共轭量和耗散空间的Drucker 塑性公设,采用纯简化有效应力和有效吸力这一对双应力变量,建立了考虑吸附水的土水完全耦合的非饱和土弹塑性理论框架,据此获得采用净应力和吸力表示的弹塑性柔度矩阵,用于采用上述本构理论建模时理论模型与土工试验成果之间直接相互验证。     

柔韧性概念在沙生植物中的应用

 植物柔韧性是沙生植物抗风蚀的重要影响因子,柔韧性的研究可对风蚀治理措施的选取及沙地风蚀方程的建立提供一些理论依据。回顾和总结国内外植物柔韧性的研究现状,提出沙生刚性植物和柔性植物的概念,指出现在研究中的不足和今后的研究方向即植物柔韧性的量化测定,柔性植物及刚性植物作用机理,柔性植物与刚性植物的划分和界定,以及植物柔韧性在风洞中的模拟。     

气举反循环清理地下连续墙槽底沉渣数值分析

为了深入研究用气举反循环清除地下连续墙槽底沉渣的效果,采用Fluent软件,运用模拟数值分析的方法,建立二维模型,并以气举混合器安置深度、空压机清槽压力、沉渣直径为研究对象,得出了如下结论：气举反循环技术能够有效地将沉渣从连续墙基坑底部返出,沉渣的出口速度范围在0.014～1.098 m/s,粘粒的逃逸速度比其它粒径的逃逸速度大;沉渣厚度越大,沉渣清理出来越难。     

苏州粉土地层地连墙施工对地层扰动影响研究

采用三维有限差分软件FLAC3D对地下连续墙施工进行模拟,分析苏州地区粉土地层中地连墙施工对土体扰动及周边建筑物影响。利用UBCSAND硬化规律对外部扰动作用下土体强度逐步发挥的力学特性进行表征,模拟开挖过程中浅层土体变形,并对地连墙施工中成槽开挖、钢筋混凝土施工及混凝土硬化进行全过程模拟。计算结果表明,硬化模型较好地反映地连墙施工扰动下浅层土体力学特性;地连墙成槽阶段地层变形随深度的增加而减小,地表以下20 m范围内地层变形显著,而深部土体变形较小;钢筋混凝土浇筑施工对地层变形起到抑制作用;混凝土硬化阶段地层变形趋于稳定。在该基础上采用硬化模型对苏州某基坑地连墙施工进行数值仿真,模拟结果和现场实测吻合较好。     

安徽同马大堤的渗控监测

针对同马大堤加固工程中所采用的水泥土防渗墙的渗控措施,对2个监测断面历时3年的测孔水位资料进行了分析,揭示了长江水位与堤基渗流的变化规律。观测资料显示,洪峰期间,堤基水位与江水位明显相关;汛期防渗墙前后水位差较大,充分显示了水泥土防渗墙截渗效果。     

Localization analysis in softening RC frame structures

This paper discusses the sensitivity of softening reinforced concrete frame structures to the changes in input ground motion and investigates the possibility of localizations for this type of structure in static and dynamic analysis. A finite element model is used in which the sections resisting force are calculated using a proposed differential hysteretic model. This model is especially developed for modelling softening behaviour under cyclic loading. To obtain parameters of the differential model the moment–curvature of each section is evaluated using a microplane constitutive law for concrete and bi‐linear elasto‐plastic law for reinforcements. The capability of the procedure is verified by comparing results with available experimental data at element level, which shows good accuracy of the procedure. The effect of possible changes in ground motion is assessed using a non‐stationary Kanai–Tajimi process. This process is used to generate ground motions with approximately the same amplitude and frequency content evolution as those of base ground motion. The possibility of localization in static and dynamic loading is investigated using two structures. A measure for the possibility of localization in code‐designed structures is obtained. This study indicates that localization may occur in ordinary moment‐resisting structures located in high seismic zones. Localization may result in substantial drift in global response and instability due to P–δ effect. Also, it is shown that the structure becomes very sensitive to the input ground motion. It is concluded that allowance by some design codes of the use of ordinary moment‐resisting frames in regions with high seismicity should be revised or improvements should be made in the detailing requirements at critical sections of these structures. Copyright © 2002 John Wiley & Sons, Ltd.     

基于形式化描述的柔性工作流建模方法

分析了柔性工作流的特性,提出了一种实现柔性工作流的建模方法,对工作流中主要元素进行了形式化描述,给出了该柔性工作流建模方法的实例。     

深基坑逆作法技术探讨

随着城市建设的发展，更多的高层建筑出现在建筑密集的市区。由于建设的场区狭小，地下管网密集，给设计和施工留有的空间很小，同时在基坑开挖过程中，还必须充分考虑到周围建筑物的保护问题。逆作法技术成功地解决了这一问题。在阐明逆作法工艺原理的基础上，进一步探讨了逆作法的主要技术特点、技术措施及其存在的问题。     

OPINIONOpen‐minded Geographers: Their Potential Role in Integrated Adaptive Environmental Management

There are three key factors to be considered in comprehensive environmental management: (a) integration across disciplines and interests; (b) flexibility and adaptability based on feedback; and (c) interactions between policy and implementation at different scales. Successful management is both integrated and inclusive, and also adaptive and flexible. It involves a synthesis of work, requiring empathy among contributors and active synthesis. Furthermore, there is a need for a dialectical consideration of processes acting at various scales. Geographers who are not too narrowly specialised have a key role to play, and, collectively, might have been more centrally involved in environmental management than they have been.     

连续墙开槽机

随着地下建筑深度的徊深，惯用的抓斗挖掘技术已不适应其需要，应运而生了连续墙及开槽技术。本文对开槽机作了介绍。