玄武岩纤维与钢筋锚杆锚固性能现场对比试验研究

玄武岩纤维（BFRP）锚杆具有抗拉强度高、耐腐蚀性能好等优点,是岩土锚固结构中钢筋的良好替代品,近年颇受业界关注。通过在黄土地层中开展4组?25 mm BFRP锚杆和钢锚杆的现场拉拔试验,初步研究两种材质锚杆的破坏模式和锚固性能差异。研究结果表明：对于诸如?25 mm类较大直径土层锚杆,拉拔过程中锚固体系的灌浆体内外界面破坏迹象共存,但最终破坏模式受控于灌浆体与土层界面（第二界面）,且BFRP锚杆与砂浆内界面（第一界面）破坏程度明显高于钢锚杆;两种材质锚杆的极限承载力相近,界面黏结强度均随锚固长度的增大而减小;受两种材质锚杆本身的加工工艺和材料力学性能影响,试验中钢锚杆与灌浆体的黏结性能优于BFRP锚杆;相同荷载水平,相同位置处,BFRP锚杆杆体轴力大于钢锚杆,轴力衰减速率略小于钢锚杆;峰值剪应力BFRP锚杆小于钢锚杆。     

卸荷岩体锚固预应力损失的影响因素分析

讨论了影响卸荷岩体锚固预应力变化的岩体应力状态、岩体性质与流变、锚固时间、钢材松弛、施工质量、锚索结构与环境变化等因素,得出了不同因素对卸荷岩体锚固预应力损失的影响效应,并分析了各种影响因素与预应力损失的耦合作用,得出了相关的结论。     

Impacts of annual precipitation extremes on soil and nutrient losses in vineyards of NE Spain

The objective of this research was to characterise annual precipitation extremes in a Mediterranean vineyard region. The number of exceptional events (P > 95th percentile) and annual extreme events (P > 99th percentile), as well as their strength, erosive character and return period were analysed for 2000–2004. The erosive character was evaluated according to the R‐factor (kinetic energy × maximum intensity in 30‐min periods). Soil and nutrient losses caused by these events were evaluated by combining field sampling and a hydrological model to estimate total runoff in a vineyard plot. The results show a clear increase in the number of very wet days and extreme events (P > 95th percentile), which represented up to 88% of annual rainfall. The severity of the extreme events (TS = precipitation event P > 99th percentile) reached values higher than 50 mm almost every year. These values were far exceeded in 2000, when one extraordinary event recorded 50% of the annual rainfall, with TS of 189 mm, about 80% of total rainfall being lost as runoff. Annual erosivity was driven not only by extreme events, but also by short events of less depth but high intensity. During some of the years analysed, rainfall erosivity was two or three times the average in the area. Most soil and nutrient losses occurred in a small number of events: one or two events every year were responsible for more than 75% of the annual soil and nutrient losses on average. Antecedent soil moisture conditions, runoff rates, and events with a return period higher than two years were responsible for the higher erosion rates. Apart from an exceptional event recorded in 2000, which produced more than 200 Mg ha^?1 soil losses, annual soil losses up to 25 Mg ha^?1 were recorded, which are much higher than the soil loss tolerance. Copyright © 2008 John Wiley & Sons, Ltd.     

红外热成像技术在震后房屋损坏快速鉴定中的应用研究.

本文引入了目前地震现场房屋快速安全性鉴定工作的辅助手段——红外热像无损检测技术,借用图像处理手段、数学统计方法等,探讨了震后房屋破坏红外图像的表现效果,分析了红外图像与各影响因素的关系.文中以汶川地震现场建筑物的典型震害为代表,重点分析了框架结构、砖混结构、简单结构房屋的红外图像表现.本文所涉及的建筑材料主要有水泥砂浆、钢筋混凝土、红砖、黏土、楠木、石棉瓦、水泥板等:表面装饰层材质有红漆、白色抹灰、黄色涂料、白色壁纸、红色瓷砖、白色瓷砖等.材料的物理性质不同,其表现出的红外图像特征差别较大.统计相关分析结果显示:图像的表现效果在下午时段优于中午时段和上午时段;晴天拍摄图像的表现效果最佳,雨天次之,阴天最差.同时,要考虑红外热像无损检测技术检测漏水破坏的优势,充分利用雨天对建筑物破坏的影响;光照射情况与红外图像表现效果的关系为:直面照射条件优于倾斜照射和不能照射;破坏程度相关分析统计结果显示,构件的“基本完好、轻微破坏、中等破坏”这3个破坏等级,随着破坏程度的递进,图像的表现效果增强;而构件的“中等破坏、严重破坏、毁坏”这3个破坏等级,随着破坏程度的递进,图像的表现效果无显著变化;对结构类型数据统计结果显示,底框架结构图像的表现效果优于砖混结构、框架结构和简单结构;装饰层材质分类相关统计分析结果显示,图像表现效果与材质性质、颜色、表面粗糙状况等因素有关.     

中国大陆百年（1901~2001年）浅源强震活动及生命损失回顾与分析

简要回顾和初步分析了中国大陆百年（1901~2001年）浅源地震活动（MSge;6.0）及生命损失的某些特征.1901~2001年中国大陆发生约420次6级以上的浅源强震， 其中88％发生在大陆西部. 其原因可能与西部活动地块的变形与运动相对强烈有关； 大陆西部的平均震源深度(25 km)比东部(16 km)的深， 这可能与大陆西部地壳厚度比东部明显的厚有关； 震源深度随深度的不均匀分布， 可能与地壳断层摩擦学和流变学性质随深度变化有关； 大陆浅源强震活动呈现时 空群集的过程； 反映地震强度分布的震级(MS)-频度(Nc)关系是lg Nc ＝8.64－0.99 MS. 在1901~2001年间地震造成生命损失约60余万人，其中， 河北省和宁夏回族自治区损失最大， 地震死亡人数分别约是250 700和246 200人； 地震死亡人数与地震震级的统计关系并没有显示出一种良好的线性相关关系， 表明地震生命损失除了与地震释放的能量和地面震动大小有关外， 还应与地震发生的时间、 地震区的建筑物破坏程度和人口密度等多种因素直接相关.地震死亡人数（D）及其事件的累计频度（Nc）的关系是lg Nc＝2.40－0.39lgD， 表明地震死亡人数的分布是分形的.      

陕西省黄河流域泥沙流失变化分析

本文以陕西省黄河流域为研究对象,运用实测水文资料,根据水沙平衡原理,分析计算了陕西省黄河流域出、入境和自产径流量、输沙量。通过对自产水沙量的变化分析,寻找本省黄河流域水沙变化的特点和主要影响因素。阐述了泥沙流失的分布区域,并以泥沙流失的重点区域无定河流域为典型进行深入分析,从而进一步为陕西省水土保持、水资源保护和生态建设提供决策依据。     

An analysis of medium losses in coal washing plants

A major operating cost in dense-medium separation is in replacement of lost medium solids. The loss of medium solids, being costly, plays a crucial role in determining the economics of any preparation operation. Coal washeries that employ dense-medium cyclones often attempt optimization of the processes by varying the vortex or the spigot diameter and the feed relative density. While these changes help in closer control of the separation process, they also result in medium losses due to changes in the medium split ratio (ratio of the medium flow rate in overflow to underflow). Since medium solids are lost by adhesion to products and as magnetic separator effluent, the effect of the change in medium split ratio on the drain-and-rinse screens and, hence, the magnetic separator circuit needs to be studied. In Tata Steel's coal washeries, at Jharkhand India, which employs primary and secondary dense-medium cyclones in series to produce clean coal, middlings and rejects, reducing the relative density of feed medium, had an insignificant effect on the medium split ratio. On the other hand, changing the cone ratio (ratio of the overflow diameter to the underflow diameter) changed the relative density and the flow rates through the cyclone outlets, thus affecting the performance of the magnetite recovery circuit.A systematic study through laboratory tests and a detailed plant sampling campaign helped in identifying the causes of magnetite loss. Upon implementation of the recommendations, the magnetite losses decreased, resulting in a saving of approximately US$27,500 per annum. The study also helped in evolving some checkpoints for plant operators for identifying magnetite losses.     

On predicting upland erosion losses from rainfall depth

Point rainfall triggers the complex processes of overland flow and surface erosion. The probability density functions of rainfall duration and intensity are coupled with a physically based dynamic formulation of rainfall-runoff-sediment transport relationships for upland areas. When considering a single storm, rainfall depth alone is a poor predictor of sediment transport because of the dispersion introduced by the effect of rainfall intensity. On a long terms basis, however, the total amount of rainfall can be used to predict total erosion losses.     

产业网络灾害经济损失评估研究进展

开展产业网络灾害经济损失评估研究,是理解产业网络脆弱性和潜在风险,科学指导灾前风险防范及灾后恢复重建决策的关键环节。本文从产业网络中灾害扩散的角度,对其造成的经济损失类型及研究进展进行了系统梳理。结果表明,产业物理损失方面,主要通过建立灾害强度参数与厂房建筑、生产设备及存货等物理损失程度间的脆弱性曲线进行评估。受灾产业中断损失方面,应关注其组合投入要素物理受损情景下的生产能力损失程度(PCLR)。产业网络灾害波及损失方面,主要存在微观“企业供应链网络”和宏观“产业链网络”二种研究尺度。其中,前者以微观企业个体为基本粒度,利用复杂网络分析方法,模拟灾害依托企业供应关系扩散的空间过程及其造成的供应链中断损失;后者以聚合的产业部门或区域为基本粒度,利用投入产出(IO)、可计算一般均衡(CGE)等宏观经济计量模型,模拟灾害在产业部门或区域间的扩散过程及其造成的宏观区域经济损失。最后,从情景分析的视角,构建包括灾害事件场景、产业网络暴露、节点物理损失和中断损失、供应链网络中断损失、宏观产出损失于一体的多过程、多尺度经济损失集成评估体系,以综合模拟灾害损失在产业网络中的放大效应。     

An influencing mechanism for ecological asset gains and losses and its optimization and promotion pathways in China

Journal of Geographical Sciences - Accounting for the gains and losses of ecological assets holds scientific significance in sustaining human well-being. Based on related research on ecological...