细粒尾矿快速筑坝新技术及工程应用

为解决传统细粒尾矿上游式筑坝方法面临的坝基承载力不足、排渗加固滞后、防洪超高不足等难题,以满足企业大规模生产时快速筑坝的实际需求,通过开展细粒尾矿软滩模袋法堆坝工艺、尾矿库快速堆坝工业示范、坝体稳定性评估等研究,提出集尾矿模袋法强基、宽顶子坝增稳、坝基协同排渗为一体的细粒尾矿快速筑坝新技术及配套施工工艺.结果表明:经过...     

Fish-Passage Facilities as Ecological Traps in Large Neotropical Rivers

Abstract:  At present most of the large rivers of South America are impounded. Management plans historically have relied on the construction of fish passages, specifically ladders, to mitigate the impact of these waterway blockages on fisheries and biodiversity. Nevertheless, the design of these facilities is not ecologically sound and they are not monitored continually. Consequently, the real role of South American fish passages in fisheries and biodiversity management is unclear and the results of some studies suggest that ladders are problematic in fish conservation. We examined the characteristics and negative aspects of fish passages within a larger context and considered the notion that these facilities are ecological traps in some Brazilian impoundments. Four conditions are required to characterize a fish passage as an ecological trap: (1) attractive forces leading fish to ascend the passage; (2) unidirectional migratory movements (upstream); (3) the environment above the passage has poor conditions for fish recruitment (e.g., the absence of spawning grounds and nursery areas); and (4) the environment below the passage has a proper structure for recruitment. When these conditions exist individuals move to poor-quality habitats, fitness is reduced, and populations are threatened. To exemplify this situation we analyzed two case studies in the upper Paraná River basin, Brazil, in which the four conditions were met and migratory fish populations were declining. If passages work as ecological traps, regional fisheries will be in danger of collapse and conservation policies toward biodiversity will become more difficult and ineffective. The situation demands the closing of the passage in conjunction with alternative management actions to preserve system functionality, especially the conservation of critical habitats downstream and the restoration of damaged habitats in the region.     

Local Responses to Inundation and De-Farming in the Reservoir Region of the Three Gorges Project (China)

Large-scale infrastructural developments in rural areas often impose significant direct and indirect impacts on environment and people. The Three Gorges Project to dam the Yangtze River in China will create a huge reservoir, inundate farmlands and villages, and incur large-scale resettlement. The concurrent de-farming program to reforest marginal farmlands on steep slopes imposes additional stresses on local people. This study evaluates the ecological and economic adjustments in rural areas affected by both projects, and explores villagers’ knowledge, attitudes, perceptions, and expectations vis-à-vis the drastic changes. Eleven villages in Yunyang County in Sichuan Province, stratified into three zones based on topography and agriculture, were assessed by field studies, questionnaire surveys, maps, satellite imagery, and census and government reports. Multiple regressions identified predictors for 17 dependent variables. Spatial variations in the difficult terrain imposed zone-differentiated agricultural constraints, ecological impacts, and human responses. The dominant farming population—mainly young adults working as migrant laborers in cities—has adopted some nonagricultural work to supplement incomes. Expected per-capita standardized farmland (SF) exceeded threshold SF, which surpasses existing SF. Motivations to reclaim more farmlands, de-farm marginal lands, and become migrant laborers were explained by different multiple-regression predictors. Reduction in farmland stock by inundation and de-farming, aggravated by unwillingness towards nonlocal resettlement, would impose ecological pressures and stimulate demands for nonfarming incomes. Common anticipation of better future income and occupation has been subdued by unfavorable feedbacks from early relocatees. Future environmental and landscape changes are hinged upon changing human responses. Government policies could be informed by research findings to match economic, ecological, and social realities.     

宁夏长宁天然气管道工程植被恢复验收监测方法初探

探讨了长距离输气管道工程埋设过程中造成的带状植被破坏后的恢复监测验收方法。采用定性踏查和选择有生态环境代表性的样地样方法定量检验植被的恢复程度是可行的。     

汽车制造业验收监测中排气筒等效计算的探讨

通过对某一汽车制造企业等效排气筒组的实际监测与相关参数计算的分析,讨论并提出了对此类排气筒组等效排气筒高度的计算方法.     

电镀行业验收监测案例分析

以某电镀企业验收监测为例,介绍了验收监测项目的概况,主要污染源、污染物及其治理设施,验收监测的内容,验收监测的质量保证措施,验收监测的侧重点和难点,并且探讨了验收监测中遇到的其他问题。     

尾矿坝溃坝后果严重度评价模型研究

尾矿库是一个具有高势能的人造泥石流,一旦溃坝将给当地的工农业生产及尾矿库下游的人民生命财产造成巨大的灾害和损失.分析并提出了影响尾矿坝溃坝后果严重程度的4个主要影响因子(尾矿坝规模、生命损失、经济损失和社会环境影响),依据现行法规,对各影响因子进行了分级,利用综合因子加权法构造了尾矿坝溃坝后果严重度的评价模型,给出了判别严重程度的定量指标.该模型的建立,为尾矿库的风险管理提供了依据.     

混凝土重力坝的地震响应分析

进行了某混凝土重力坝在多遇和罕遇地震荷载作用下的二维地震响应分析,比较了水位条件对大坝动力响应的影响。研究表明,在多遇地震荷载作用下,大坝应力应变关系基本处于弹性状态,在罕遇地震荷载作用下,最大地震动位移出现在大坝上侧,随着水位的上升,大坝上侧的位移和坝踵处动应力逐渐减小,而下游坝面折坡处的动应力基本不变。     

一种基于BP网络和粒子群算法的拱坝可靠度分析方法

为了进行极限状态方程不明确的大型结构可靠度分析,提出了结合神经网络和粒子群优化计算拱坝可靠度的算法。确定性力学分析采用ANSYS软件,利用BP神经网络来模拟高度非线性映射关系的功能函数,基于罚函数和粒子群优化法进行可靠指标计算。综合C语言、ANSYS的APDL二次开发以及MATLAB混合编程技术,编制了该算法的可靠度分析程序。算例表明,该方法适应于隐式功能函数的复杂结构可靠度分析。     

思林水电站碾压混凝土坝的渗流分析

碾压混凝土重力坝的坝身及地基渗径是筑坝中的关键技术问题。文章是以思林水电站碾压混凝土重力坝为研究对象,以大型通用有限元软件ANSYS为平台,其核心是对坝基有相互作用的整体坝段数值模型的建立以及利用程序对典型坝段的渗流场进行二维有限元渗流计算分析,研究碾压混凝土坝渗透特性及其影响因素,并证明了这种分析方法的可行性。