碾压混凝土坝施工气候信息实时监控理论与应用

在分析了基于仓面施工气候信息实时监控的碾压混凝土施工质量控制措施基础上,提出了监 控中VC值(vibrating-compacted value)的调控方法,构建了监控的概念模型,并进行了其系统设计。 该系统成功应用于官地水电站碾压混凝土坝施工质量实时控制中,实现了仓面施工气候信息的自动采 集、存储、查看和分析。通过预测VC值损失量及其对其他施工措施的影响,该系统实现了反馈控 制,为保证工程质量发挥了重要的作用。     

丰乐拱坝加厚新老混凝土结合处理效果评价

目前拱坝贴厚加固处理大多采用经验方法,为解决拱坝贴厚加固工程的安全性和经济性问题,采用ANSYS有限元计算程序对丰乐拱坝加厚新老混凝土结合处理措施进行非线性有限元分析。选取新老混凝土结合处理的锚杆设置参数(锚杆直径、间距、锚杆埋入老混凝土的深度)及参数水平作为变量,以正交试验设计的思想来安排有限元试验方案,并选取新老混凝土结合面的开裂度作为评价指标。计算结果表明,加厚处理时新老混凝土用锚杆联结可以有效地减小结合面的开裂度,并给出了经济有效的锚杆设置方案。     

工程运行期的文化遗产保护与利用研究——三峡工程博物馆策划

三峡工程进入运行期,众多机械设备面临着闲置和废弃的问题,场地特征即将消失。基于工业遗产保护与利用的趋势与先进经验,梳理和调查了三峡管理区的工业遗存,结合泛博物馆设计理念,提出了三峡工程博物馆的策划方案,为工程运行阶段的水利工程文化建设提供借鉴。     

百米级硬填料坝结构安全度分析

硬填料坝(Hardfill坝)是一种新坝型,Oyuk坝是世界上仅有的两座高度超过100 m的硬填料坝之一。对该坝在正常运行工况以及地震工况下的大坝工作性态进行了弹塑性有限元分析,并运用水荷载与地震荷载超载法探讨了Oyuk坝在静动条件下的破坏模式与安全度。研究结果表明,在正常运行工况以及OBE地震工况中,Oyuk坝全断面受压,坝体强度安全系数与抗滑稳定系数均较高,坝体基本处于弹性工作状态。由于该坝在坝底、坝踵设置混凝土分区、并在坝趾区采用了高强度硬填料等措施,在水荷载及地震超载分析中具有很高超载安全度。     

沐若水电站大坝碾压混凝土石粉掺和料应用研究

沐若水电站大坝为全断面碾压混凝土重力坝,因当地人工砂的细度模数小,石粉含量高,为降低工程造价,合理利用资源,减少对环境的污染,对石粉作为掺和料进行了一系列现场试验研究。结果表明,只要采用合适的加工工艺控制人工砂的石粉含量在27%以下,以内含的方式按砂质量3%~4%的石粉作为掺和料配制碾压混凝土,就完全可以满足设计对碾压混凝土各项性能指标的要求。此项成果已成功应用于工程实际,取得了较好的效果。     

碾压砼施工技术在高摩赞大坝中的应用

本文阐述了碾压砼筑坝施工技术的概念,及国内外碾压砼坝的发展情况,详细介绍了高摩赞大坝砼运输及入仓方式、碾压砼分仓、碾压砼大坝施工方法和碾压砼施工注意事项,通过高摩赞碾压砼大坝施工分析,体现出了碾压砼施工在降低成本、机械化程度高等方面的优点,得出了值得广泛推广和应用的结论．     

中国与东南亚国家贸易潜力及影响因素研究——基于随机前沿引力模型

运用时变随机前沿引力模型和贸易非效率模型,以1998-2016年中国及东南亚九个国家面板数据为样本,测度中国对东南亚国家出口贸易潜力,并分析其主要影响因素。结果表明：1998-2016年中国对东南亚国家出口贸易潜力呈现先上升后下降趋势,依然有较大提升空间,中国对东南亚国家出口贸易潜力差异较大。航空运输货运量、货币自由度、财务自由度、商业自由度及世界贸易组织成员国均对出口贸易非效率具有显著的影响。     

The future of India's obsolete dams: Time to review their safety and structural integrity

India has built over 5000 large dams till date to boost electric power and to enhance irrigated agriculture. In spite of this big dam building venture, India lacks expertise in decommissioning old dams. As a matter of fact, India has more than 500 large dams that were built 50 years ago, and 100 of them have passed over a century. This article analyses the existing facts on India's outdated dams, their safety matters and recommends future strategies to safeguard the large dams from potential future threats.     

The use of landslide hazard maps to determine mitigation priorities in a dam reservoir and its protection area

Despite longstanding research on the landslide hazard assessment and mapping, the use this information in regional planning applications remains largely unclear. There is still a need for novel methods to interpret the results of hazard analyses. In this respect, the main research question of this study is how the landslide hazard maps can be evaluated in planning practice. To evaluate this issue, a comprehensive case study was carried out and a new methodology, defining the order of priority for the locations where mitigation measures are applied was developed. The investigations were carried out in the Melen Dam reservoir, which provides potable water to the city of Istanbul, and the dam protection area (Duzce, Turkey) in four main stages: (i) Evaluation of the general characteristics of the study area, (ii) preparation of landslide inventory, (iii) development of landslide hazard model, and (iv) implementation of the results of hazard analyses in planning. As a consequence, a decision support system that can evaluate analytically complicated outputs “P_Combined”, “P_{AL min.}”, and “L_Total” and provide clear decisions “Urgent”, “Primary”, and “Secondary” was suggested. Considering the limited resources available for the mitigation measures, the determination of mitigation priorities for the micro-catchments constitutes the key land-use policy for the protection of the dam reservoir.     

Estimating the gravity model when zero trade flows are frequent and economically determined

ABSTRACT

Since the 1950s, we have known that the presence of zero-valued dependent variables can seriously bias econometric estimates whether the zeros are included or excluded. Yet the widely-used gravity model is frequently estimated on samples that include large fractions of zeros. An influential paper by Santos Silva and Tenreyro – based on simulations that include no economically-determined zeros – concludes that the bias problems resulting from zeros and those resulting from heteroscedasticity and nonlinearity can be solved using the Poisson Pseudo-Maximum-Likelihood (PPML) model including the zero values. This paper begins by adapting the Santos Silva and Tenreyro experimental design to include economically-determined zeros to see whether this conclusion continues to hold. With this design, it finds that alternative estimators have lower bias than PPML. Changing to a Monte Carlo design that replicates the much-higher real-world frequency of predicted values near zero restores the finding of lower bias with the PPML estimator. The results highlight the need for very careful design of Monte Carlo experiments when evaluating alternative estimators of the gravity model.