水布垭面板堆石坝的三维弹塑性数值分析研究

在建的清江水布垭面板堆石坝高达233 m,是目前同类坝型中最高的.采用MSC.Marc非线性有限元程序,发展了三维子模型法,对该坝进行了三维弹塑性有限元仿真分析,模拟了面板的分缝、坝体材料分区、填筑及蓄水过程,采用双屈服面弹塑性模型模拟堆石体的变形特征.根据数值分析的结果,对坝体和面板的应力变形分布规律进行了探讨.     

Zircon U-Pb and oxygen isotope evidence for a large-scale O depletion event in igneous rocks during the Neoproterozoic

Oxygen isotope analysis and U-Pb dating were carried out on zircons from granite, granitic gneiss and eclogite in the Dabie-Sulu orogenic belt of east-central China. The results show a wide variation in zircon δ¹⁸O values from −10.9 to 8.5‰. Most of the values are lower than normal mantle zircon and almost half have prominently negative values. The low δ¹⁸O zircons have protolith ages of 700 to 800 Ma and metamorphic ages of 205 to 250 Ma, respectively. Fluid availability within the metaigneous rocks dictates the extent of metamorphic recrystallization and overgrowth. The igneous zircons have preserved their magmatic zoning and middle Neoproterozoic U-Pb age during the Triassic metamorphism, indicating low fluid availability. Widespread low δ¹⁸O values are identified in the magmatic zircons of middle Neoproterozoic age, within an outcrop area of over 20,000 km² along the northern edge of the South China Block. The low δ¹⁸O zircons record the presence of large volumes of low δ¹⁸O igneous rocks that were derived from remelting of meteoric-hydrothermally altered rocks at some time between 700 and 800 Ma.The U-Pb ages for metaigneous protoliths and granites are correlated not only with the timing of rifting accompanying the breakup of Rodinia, but also with contemporary glacial deposits in the South China Block at paleolatitudes of 30 to 40°N. Melting of glacial ice and snow is suggested, instead of the direct involvement of meteoric water, to produce the low δ¹⁸O fluid with oxygen isotopic signatures like the cold-climate meteoric water. The rifting created conditions favorable to anatexis of meteoric-hydrothermally altered rocks. Glaciated regions supplied copious water for the water-rock interaction during magma emplacement along rifting zones. Both rifting and glaciation favored the generation of the low δ¹⁸O magmas in the region. The low δ¹⁸O zircons are thus interpreted to have crystallized from the low δ¹⁸O magmas of middle Neoproterozoic age, and onset of the generation of low δ¹⁸O magmas in the northern margin of the South China Block is estimated to occur at about 758 ± 15 Ma. The large-scale remelting of hydrothermally altered crust not only results from repetitive emplacement of mafic magmas along the rifting zones with protracted episodes of water-rock interaction, but also involves rift systems that rapidly introduce large volumes of fluid through confined pathways and traps in a short space of time in response to tectonic triggers. Occurrence of the large-scale ¹⁸O depletion during the middle Neoproterozoic may be a manifestation of the cold paleoclimate related to the snowball Earth event.     

青藏高原的水塔功能

青藏高原是维持我国乃至东亚地区生态系统的重要水塔。高原平均海拔在4000m以上,与周边地区形成了巨大的地势差。高原东南部不仅具有丰富的降水,而且在3500m以上以冰川雪被形态储存了巨大的水资源,因此,高原具有重要的水塔功能。基于高原潜在输出总水量和不同海拔区域水体所具有的势能两个方面,建立了高原水塔功能的模型,从而利用GIS方法,通过对我国1∶400万系列图和相关资料的统计分析,计算出高原不同高度带贮存的大气降水、冰川储水量、湖泊水量以及工农业用水量。计算结果表明,青藏高原冰川湖泊的淡水储量达39921×108m3,其中冰川储水量为39228×108m3,可利用湖泊储水量为693×108m3,平均每年由降水获得的水资源量为8495×108m3,高原工农业用水量为129×108m3。因此,高原的输出水量即出境河川径流量为6870×108m3。高原储水主要分布在海拔3000～5000m间,与高原周围相比,平均势差在2000～4000m间,最大的势差达5500m。水体具有巨大的势能,在势能的作用下,自然向周边区域输送汇集,维持着周边地区的生态过程和社会经济活动,因此,青藏高原的水塔功能对于周边地区的生态系统和社会经济系统是极其重要的。     

贡嘎山东坡海螺沟的河川径流特征

对贡嘎山高山水文观测试验系统进行了简要介绍，并对海螺沟冰川河以及黄崩溜沟的径流特征进行了初步探讨。由于大气降水同是冰川河及黄崩溜沟径流的重要补给来源，故其径流量的季节变化明显带有大气降水过程的烙印，显得丰、枯分明。在冰川河，冰雪融水和地下水在枯水季节的稳定补给改变了大气降水对冰川河径流的年内分配过程；在黄崩溜沟，由于冰雪融水和地下水对其径流的补给非常有限，大气降水过程对其径流过程的影响便明显大过冰川河。     

Nio海区冷暖事件的小波功率谱分析

根据NOAA/CPC发布的1950.1~2003.12期间Ni?o海区的SSTA资料,采用小波变换方法分析了SST变化的多时间尺度结构及其强度变化。结果表明,Ni?o各海区的SSTA序列表现出多层次相互嵌套的时频结构,经检验存在着2~7a、8~20a和30a以上尺度的变化周期;10a以上和1a以下时间尺度的周期信号能量较弱,显著性变化周期的能量主要集中在2~7a的周期振荡上;同一事件在不同海区的频率结构也不完全相同,冷暖事件的振荡能量和显著性水平从东向西有低频增大而高频减弱的变化趋势,时域中1970年以后尤为明显。     

川滇地区单断裂强震区与多断裂强震区

以《全国小震目录》(1965年1月1日～2002年lO月31日)和《四川地震台网快报目录》(2002年11月1日～2003年9月30日)为基础资料，研究了川滇地区地震活动性发展变化的主要特征，并提出“单断裂强震区”和“多断裂强震区”概念。发现川滇地区主要单断裂强震区在发生一些强震之后，已经陆续进入地震平静时段，近期发生强震的能力明显减弱。与此同时，“滇西南”、“龙陵-腾冲”、“丽江-武定”地区分别在较短时段内发生多次强震，表明这几个多断裂强震区陆续进入活跃时段，成为1984年以来川滇地区的地震主体活动区域。多断裂强震区具有区内中小断裂汇集、地质构造复杂、地震活跃时段多次出现、在同一活跃时段内又具有活跃小段与小段间距的小段组合形式等特征。对已有的和可能新生的多断裂强震区进行早期判定，以及对活跃时段、小段组合进行动态跟踪，对于川滇地区地震预报具有重要意义。     

吉林海沟金矿矿山地质环境及其恢复治理方法

在对海沟金矿矿山地质环境调查基础上，针对矿区存在着的问题，提出了治理与防范措施，对同类矿山有借鉴作用。     

惰性气体法测定地下水入渗补给量

地下水入渗补给量是重要的水文地质参数。本文介绍了测定地下水入渗补给量的最新方法——惰性气体法的原理与方法，该方法适用于封闭条件下的深层地下水。     

Element mobility during pyrite weathering: implications for acid and heavy metal pollution at mining-impacted sites

Based on back scattered electron images and electron micro-probe analysis results, four alteration layers, including a transition layer, a reticulated ferric oxide layer, a nubby ferric oxide layer and a cellular ferric oxide layer, were identified in the naturally weathering products of pyrite. These layers represent a progressive alteration sequence of pyrite under weathering conditions. The cellular ferric oxide layer correlates with the strongest weathering phase and results from the dissolution of nubby ferric oxide by acidic porewater. Leaching coefficient was introduced to better express the response of element mobility to the degree of pyrite weathering. Its variation shows that the mobility of S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite is oxidized to sulfuric acid and sulfate that are basically released into to porewater, and heavy metals Co and Bi are evidently released by acid dissolution. As, Cu and Zn are enriched in ferric oxide by adsorption and by co-precipitation, but they would re-release to the environment via desorption or dissolution when porewater pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may pose a substantial impact on water quality. Considering that metal mobility and its concentration in mine waste are two important factors influencing heavy metal pollution at mining-impacted sites, Bi and Co are more important pollutants in this case.     

生态城市的内涵及建设策略

生态城市是通过倡导生态理念，采用生态技术，建立生态化产业体系，从而达到社会、经济、环境的可持续发展，实现自然生态平衡、人文生态和谐的城乡统一体。从可持续发展的角度出发，利用生态学和社会学的观点，论述生态城市的内涵，提出科学的城市规划、合理的城市评价指标体系、完善的城市管理制度是实现生态城市的前提，强调只有自然生态、人文生态两手抓才能真正实现经济、社会、环境全面发展。