锶、铀在非均质含水层中迁移特性试验研究

对于地下水流场及其参数分布无序的非线性问题,污染物在其迁移便不可能服从对流-弥散方程所描述的规律。那么,锶、铀在非均匀介质中迁移会发生什么样的异常变化是提出地下水污染预测方法与模式的前提。根据野外调查的水文地质特征,设计出模拟迁移的试验研究的模式系统。试验表明,非均质试验柱的迁移曲线与均质的迁移曲线,总体特征有显著区别;透镜状和盲洞型非均质对迁移的影响及其环境效应是双向的,即有利面是降低了污染强度,且可降低10%～30%;不利面是延长了污染作用的时间,使污染作用时间延长3～5倍。另外,合理地解释了所谓“双峰”和“多峰”迁移曲线机制。     

海洋含黏粒砂土共振柱试验研究

本文利用英国GDS公司生产的RCA共振柱系统测试海洋含黏粒砂土动剪切模量,同时对比纯砂样的动剪切模量,系统研究固结应力、初始密实度、黏粒含量等因素对砂土最大动剪切模量的影响。试验结果表明:最大动剪切模量随有效固结应力增大而增大;随初始密实度增大而增大;随黏粒含量的增加而降低。     

顶部加箍碎石桩极限承载力上限分析

针对软土区顶部加箍碎石桩复合地基,根据理论上较为严密的极限分析上限法,通过构建协调的速度场,综合考虑土重和加箍段桩侧摩阻力等因素的影响,基于能量平衡原理推导出了单桩极限承载力递推计算公式。在此基础上,利用随机优化搜索方法搜索出临界滑裂面,从而获得更为合理、严密的顶部加箍碎石桩极限承载力计算方法。最后,结合典型的工程实例进行了对比验证和参数分析,结果表明：计算结果与实测值、既有方法计算值相比相对误差在5.4%范围内,最优顶部加箍深度约为桩体半径的8倍,可为工程实践提供一定的参考。     

哈萨克斯坦地区活动地幔构造特征与地震活动性的关系(译文)

强烈地震源(M≥6)位于厚度大于10 km的活动地幔层下伏的造山带范围内,天山和高加索地下输送的热柱通道位置不一,这种因素和固结地壳构造的区域差别都影响地震活动的最大能量水平。     

钢筋混凝土分体柱的抗震机理

为揭示钢筋混凝土分体柱的抗震机理,在以前模型试验基础上,考虑隔板与单元柱之间的非线性接触及钢筋与混凝土之间的黏结滑移,数值模拟了钢筋混凝土分体柱的抗震性能。结果表明:分体柱可实现变短柱为“长”柱的设想;分体柱具有理想的变形能力和延性,延性系数达到4.0;分体柱的刚度随变形增加呈指数衰减,后期刚度退化较为缓和;分体柱具有较高的耗能能力,其耗能系数达1.44;隔板与单元柱的切向接触应力较小,可忽略隔板对单元柱的变形协调作用。进一步验证了钢筋混凝土分体柱具有理想的抗震性能,完善和发展了钢筋混凝土分体柱的设计理论和应用技术。     

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations——Ⅰ: Theory

In this paper, wind-induced vibration control of a single column tower of a cable-stayed bridge with a multistage pendulum mass damper (MSPMD) is investigated. Special attention is given to overcoming space limitations for installing the control device in the tower and the effect of varying natural frequency of the towers during construction. First,the finite element model of the bridge during its construction and the basic equation of motion of the MSPMD are introduced.The equation of motion of the bridge with the MSPMD under along-wind excitation is then established. Finally, a numerical simulation and parametric study are conducted to assess the effectiveness of the control system for reducing the wind-induced vibration of the bridge towers during construction. The numerical simulation results show that the MSPMD is practical and effective for reducing the along-wind response of the single column tower, can be installed in a small area of the tower, and complies with the time-variant characteristics of the bridge during its entire construction stage.     

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations--Ⅱ:Experiment

The possibility of using a multi-stage pendulum mass damper(MSPMD) to control wind-induced vibration of a single column tower of a cable-stayed bridge during construction was studied theoretically in part Ⅰ of this work.In this paper,the performance of the MSPMD for reducing bridge tower vibration is studied experimentally.A MSPMD model and a tower model of the bridge with geometry scaling of 1:100 were designed and manufactured.Calibration of the MSPMD model with different wire lengths is conducted to verify the analytical model of the damper.A series of tests for the uncontrolled freestanding tower,tower with cables,and tower with MSPMD model are then performed under harmonic and white noise excitations.The experimental results show that the responses of the tower model significantly decrease with the installation of the MSPMD model,which demonstrates the effectiveness of the MSPMD to mitigate the vibration of the bridge tower.     

Enzyme activities in the water column and in shallow permeable sediments from the northeastern Gulf of Mexico

The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates.     

Experimental study on slender reinforced concrete columns wrapped with CFRP

By axial compression tests on 6 reinforced concrete slender columns wrapped with carbon fiberreinforced plastic （ CFRP）, with slenderness ratio（SR） from 4. 5 to 17.5, the results show that when SR increases the retrofitting effect declines. In the case of same SR, the stability coefficient （ SC ） for the reinforced concrete（RC） columns with CFRP is much less than that without CFRP. There is 20% increase of stable bearing capacity to the former as compared with the latter when the SR in less than 17.5. The study summarized the simplified formula for SC, which provides a reference for engineering designers.     

一种新型半潜式平台概念设计研究

在详细研究影响平台综合性能的诸多因素基础上,克服现有半潜式平台存在的不足,结合自升式平台甲板可以自由升降的优点,开发了具有自主知识产权的自升式半潜多功能深海浮式（JCSM）平台。JCSM平台结合了自升式平台与半潜式平台的优势,并以平台综合性能的提升为目标进行了细节上的优化,稳性裕度大且运动性能优良,可适应干式采油、湿式采油和干湿组合式采油等不同采油模式,并同时具有钻井、早期生产、修井、油气处理与油气储运等多种功能。在详述JCSM平台的组成及性能特点的基础上,对JCSM平台进行了稳性与运动性能数值分析,并与传统半潜式平台相比较,验证了所研发新型平台性能的优越性。研究为未来海洋油气田开发提供了一种新的选择,并对全新概念的浮式平台开发有借鉴和指导意义。