圆形工作井的土反力分布特征研究

以一个加劲水泥土圆形工作井的设计实例为基础模型,考虑到加劲水泥土宏观上显示出的正交各向异性,应用正交各向异性三维实体有限元分析技术,对因顶推力引起的土反力分布特征进行了分析。分析表明,土反力分布呈“扁圆形草帽”形态,具体分布特征及分布范围主要受工作井结构各向刚度与土层刚度等因素控制。土反力分布与其影响因素间关系的规律结论对工作井的设计工作有一定的参考价值。      

Spatial distribution of some elements and elemental contamination in the sediments of Köyceğiz Lake (SW Turkey)

Elemental accumulation, distribution and relationship profiles for sediment samples taken at 81 localities in the Köyce?iz Lake were investigated. Spatial distribution maps for ten elements (Cu, Pb, Zn, Ni, Cr, Co, Mn, Mo, Al, Fe) were created using the ordinary kriging interpolation method. Statistical tests revealed that the sediments taken from areas close to the Namnam (NamSM) and Karg?cak (KarSM) stream mouths have the highest element content. In addition, sediments close to NamSM have the highest contamination, according to contamination degree and modified contamination degree values. On the other hand, sediments close to KarSM have the highest value on the pollution load index. The enrichment factor and contamination factor values of Cr and Co, and especially Ni, close to NamSM are striking and have significantly higher values compared to the rest of the lake. There are strong correlations between these three elements, which were also confirmed by cluster analysis. Ni is the element having the highest value on the geoaccumulation index. In addition, according to the toxic unit results, it was found that 84–89% of the element-based toxic effect in the lake is due to Ni alone. According to the mean effect range median quotient values, the sediments of Köyce?iz Lake have a potential to show toxic effects of at least 76% in living organisms, which is due to the high levels of Ni. According to the mean probable effect low quotient value, it has been determined that Köyce?iz Lake is at a “highly impacted” level, which is the worst possible value on the quality scale.     

中国西部生态环境变化与对策建议

中国西部地区生态环境的历史演变过程与未来可能变化趋势是科学界面对的一大难题,正确认识西部地区生态环境的演变过程与变化趋势,是西部地区社会经济可持续发展必须面对的课题,是正确制定西部大开发战略方针的重要科学基础。依托中国科学院牵头完成的《中国西部环境演变评估》研究成果,介绍了中国西部地区生态环境演变的主要特征与基本事实,主要强调近50年来全球变暖与人类活动在西部生态环境演变中的重要作用;指出未来的气候与环境变化对西部地区的经济社会发展将产生重要影响;提出了西部地区生态保护与可持续发展的对策与建议,指出西部地区的生态建设必须综合治理、突出重点,特别强调要强化对西部地区的科学研究,为西部大开发服务。     

Analysis of the rainfall variability and change in the Republic of Benin (West Africa)

ABSTRACT

The temporal variation and trends of annual rainfall distribution in Benin were examined using data from 1940 to 2015 at six meteorological stations and three raingauges stationed throughout the country. The nonparametric modified Mann-Kendal (MK) and Levene tests were applied to detect trends and heteroscedasticity, respectively. For six of the time series, no significant trends were detected. A Bayesian multiple change points detection approach was applied to the rainfall time series, and most (six of nine) exhibited abrupt change points, corresponding to the alternation between wet (before 1968 and after 1990) and dry (1969–1990) periods. No significant trends or breakpoints and changes in the variance were observed for the spatial average rainfall time series. Seven modified MK trend tests were applied; the trends are affected by the selected MK method and rainfall statistics. Oceanic and/or atmospheric influences on the rainfall in Benin were examined by investigating the correlation between the precipitation time series and several indices. Negative seasonal correlations were determined for the North Atlantic Oscillation, Pacific Decadal Oscillation and Niño3, while positive seasonal correlations were observed for the Southern Oscillation, Antarctic Oscillation and Dipole Mode Index.     

Liquefaction of silts: the Adapazari criteria

Ground failures in the form of liquefaction, loss of bearing capacity and soil softening have been observed during the 1999 Marmara (Turkey) earthquake. Research to understand the failure phenomena has been carried out since the earthquakes. This paper attempts to provide explanations to the liquefaction failure of silts in seismic conditions. Findings from a large amount of data collected in the city of Adapazari on the physical and mechanical properties of soils is presented. A geomorphological map of the city has shown that there are surprising horizontal and vertical variations of the facies due to the activity of rivers in the past. Cases of liquefaction appear to have concentrated in former backswamp areas where silts and sandy silts were deposited by crevasse splays. Properties of the soils in zones of liquefaction and non-liquefaction have been determined down to a reasonable depth by measuring the average size, clay content and liquidity index as well as cone penetration resistances with porewater pressures to discover that there is significant discrepancy among those profiles susceptible to liquefaction and non-liquefying deposits. A set of “Adapazari Criteria” is proposed which is intended to improve over the “Chinese Criteria” and is simple enough to be universally applicable. This classification is similar to the existing criteria but emphasizes more on the clay content in addition to measuring the liquid limit and the liquidity index as well as the average size.     

Multi-disciplinary earthquake researches in Western Turkey: Hints to select sites to study geochemical transients associated to seismicity

Warm and hot spring water as well as soil gas radon release patterns have been monitored in the Aegean Extensional Province of Western Turkey, alongside regional seismic events, providing a multi-disciplinary approach. In the study period of 20 months, seven moderate earthquakes with M _L between 4.0 and 4.7 occurred in this seismically very active region; two earthquakes with magnitude 5.0 also occurred near the study area. Seismic monitoring showed no foreshock activity. By contrast, hydro-geochemical anomalies were found prior to these seismic events, each lasting for weeks. The anomalies occurred foremost in conjunction with dip-slip events and seem to support the dilatancy and water diffusion hypothesis. Increased soil gas radon release was recorded before earthquakes associated with strike-slip faults, but no soil radon anomalies were seen before earthquakes associated with dip-slip faults. Geochemical anomalies were also noticeably absent at some springs throughout the postulated deformation zones of impending earthquakes. The reason for this discrepancy might be due to stress/strain anisotropies.     

土木工程结构安全性评估、健康监测及诊断述评

阐述了土木工程结构的安全性评估、健康监测及损伤诊断的必要性和迫切性，系统论述了结构健康监测和诊断的概念、理论和方法，重点讨论了传感器的优化布置、损伤识别等健康监测中的关键问题，介绍了光纤等新型传感器的应用情况，最后指出了值得进一步研究的问题。     

相邻建筑结构的模糊振动控制

本文研究了相邻建筑结构的模糊控制问题。首先,介绍相邻建筑结构体系的特点,建立体系的力学模型及运动方程;然后,进行了半主动控制研究,提出了控制的方法;最后,利用模糊控制方法实现了结构的智能控制。通过以上研究,说明相邻建筑结构相互振动控制是十分有效的,所得出的结论对实际工程的应用具有指导意义。