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.     

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。     

Water losses from a reservoir built in karst: the example of the Boljunčica reservoir (Istria,Croatia)

The paper presents the case of the Boljunčica reservoir, which began operation in 1973. It is situated on the Istria peninsula (Croatia). This is a multipurpose reservoir which was built in order to protect the downstream area from flood, to store water for irrigation, and to control sediment transport. The reservoir is situated on the contact zone between water impermeable Eocene flysch and deep Eocene and Cretaceous limestone. The bottom of the reservoir is covered partly by both flysch and quaternary deposits. Water losses from the reservoir bottom are so large that the main service intended for the reservoir, the storage of water for irrigation, is impossible. After every intensive precipitation, which occurs often in this region, the reservoir fills very quickly. The problem is that its retention of water is very short, and lasts only a few days. The water volume of the reservoir at the spillway altitude of 93.00 m a. s. l. is about 6.5 × 10⁶ m³. Because of water losses from the reservoir bottom, the mean annual volume of water stored in it, during the period of 1977–2005 was only 0.5 × 10⁶ m³, which is less than 8% of the full reservoir volume. On the reservoir bottom, many new swallow holes opened through the sediment cover after each time it filled and emptied with water. Special attention is paid to the groundwater level analyses. Interdisciplinary analyses and investigations of hydrological and hydrogeological factors causing the formation of swallow holes and water losses from the Boljunčica reservoir are discussed. The example given in this paper explains one unsuccessful case of building a reservoir in Dinaric karst, caused mainly due to insufficient geological, hydrogeological and hydrological investigations. In order to prevent water losses from the Boljunčica reservoir, very complex and expensive work needs to be done, but its success regarding the reasonable reduction of water losses from the reservoir is in question.     

天津市控制地面沉降分区管理模式研究

天津市平原区出现了不同程度的地面沉降现象,全市年均沉降速率约30mm,地面沉降造成的经济损失很大。本文采用分类赋值打分的方法,利用ArcGIS软件进行后期处理绘制天津市地面沉降分级管理区域,并提出相应的控沉管理措施。     

沈阳—抚顺地区潜在地震灾害的危险性分析

沈阳—抚顺地区位于下辽河断陷的北东缘,是郯庐断裂系（ＴＬＳ）北段主要分支的交会点和重要弯曲转折点;活动断裂弯曲转折部位、交叉部位都可能形成“粘滑闭锁段”,与地震特别是大地震的发生直接相关;同时许多大地震也和断陷盆地区的低位高角度断层（兼具有走滑性质）有关。ＴＬＳ现代的右行走滑特征及沈阳—抚顺地区所处的构造位置均反映该地区是强大地震（７级以上）的潜在发生区;强震一旦发生将造成巨大损失,潜在隐患十分巨大。应加强潜在地震的预测、预报研究。     

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.     

Flood Risk Analysis and Flood Potential Losses Assessment

The heavy floods in the Taihu Basin Showed increasing trend in recent years.In this work,a typical area in the northern Taihu Basin was selected for flood rish analysis and potential flood losses assessment.human activities have strong impact on the study area‘s flood situation(as affected by the polders built,deforestation,population increase,urbanization,etc.) and have made water level higher,flood duration shorter,and flood peaks sharper.Five years of different flood return periods[(1970),5(1962),10(1987),20(1954),50(1991)] were used to calculate the potential flood risk area and its losses.The potential flood risk map,economic losses,and flood-impacted population were also calculated.The study‘s main conclusions are:1) Human activities have strongly changed the natural flood situation in the study area,increasing runoff and flooding;2) The flood risk area is closely related with the precipitation center;3) Polder construction has successfully protected land from flood.Shortened the flood duration,and elevated water leel in rivers outside the polders;4) Economic and social development have caused flood losses to increase in recent years.