Vulnerability of floating tunnel shafts for increasing earthquake loading

Fragility curves constitute the cornerstone in seismic risk evaluations and performance-based earthquake engineering. They describe the probability of a structure to experience a certain damage level for a given earthquake intensity measure, providing a relationship between seismic hazard and vulnerability. In this paper a numerical approach is applied to derive fragility curves for tunnel shafts built in clays, a component that is found in several critical infrastructure such as urban metro networks, airport facilities or water and waste water projects. The seismic response of a representative tunnel shaft is assessed using tridimensional finite difference non-linear analyses carried out with the program FLAC^3D, under increasing levels of seismic intensity. A hysteretic model is used to simulate the soil non-linear behavior during the seismic event. The effect of soil conditions and ground motion characteristics on the soil-structure system response is accounted for in the analyses. The damage is defined based on the exceedance of the concrete wall shaft capacity due to the developed seismic forces. The fragility curves are estimated in terms of peak ground acceleration at a rock or stiff soil outcrop, based on the evolution of damage with increasing earthquake intensity. The proposed fragility models allows the characterization of the seismic risk of a representative tunnel shaft typology and soil conditions considering the associated uncertainties, and partially fill the gap of data required in performing a risk analysis assessment of tunnels shafts.     

西安市投资环境优化对策的定量研究

选取系列指标体系，运用层次分析法，采用单排序和总排序，分析比较影响西安市的投资环境的因素系列，确定其权重重要性程度，据此提出优对策。     

Seismic risk of circum-pacific earthquakes I. Strain energy release

Commonly used earthquake “whole process” frequency - magnitude and strain energy - magnitude laws are merged to obtain an analytic expression for an upper bound magnitude to regional earthquake occurrenceM ₃, which is expressed primarily in terms of the annual maximum magnitudeM ₁ and the magnitude equivalent of the annual average total strain energy releaseM ₂. Values ofM ₃ are also estimated graphically from cumulative strain energy release diagrams. Both methods are illustrated by application to the high seismicity of the circum-Pacific belt, using Duda’s (1965) data and regionalisation. Values ofM ₃ obtained analytically, with their uncertainties, are in agreement with those obtained graphically. Empirical relations are then obtained betweenM ₁,M ₂, andM ₃, which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature. For instance.M ₃ andM ₂ differ by one magnitude unit in subregions of the circum-Pacific.     

绿色招商与县域经济可持续发展——以河南省为例

以河南省县域经济发展为例论述了招商引资对于县域经济发展的重要性,并从可持续发展的角度对当前全民招商的现象进行了反思.在此基础上,讨论了绿色招商的内涵和主要原则,指出绿色招商和循环经济是实现县域经济可持续发展的关键所在.根据县城经济发展的特点,以河南省新郑市和义马市循环经济发展为例,从理论和实证的角度,对县域农业和工业循环经济两大体系构建进行了论述,并对县域绿色招商中应注意的问题,如市场有效性、招商载体构建、实体虚拟产业循环结合等进行了探讨.     

Groundwater contamination: risk management and assessment for landfills in Mar del Plata, Argentina

 This study presents a program for risk management in the contamination of groundwater resulting from leachate in landfills at Mar del Plata (Argentina). The program includes prediction, prevention, monitory observation and mitigation as actions that must be taken prior to, during, and after contamination occurs. This routine aids in the identification of weak points and failures of the program for those who are in charge of making decisions, and will allow better use of limited financial and technical resources based on planning, thus minimizing disconnected determinations. Results of the prediction stage were confirmed through monitoring. The presence of a plume of contamination more than 100 m from the landfill was shown, thus proving that implementation of a monitoring plan to follow the development of the contaminated plume must be implemented, particularly in populated areas which depend on residential wells for their water supply. Received: 8 May 2000 · Accepted: 14 August 2000     

An assessment of the risk from future eruptions of the Soufriere volcano of St. Vincent,West Indies

The Soufriere volcano is a 1220 m high stratovolcano which occupies the northern part of the island of St. Vincent. It is one of the most active centres of volcanism in the Caribbean and has a record of activity dating back to the Pleistocene. Historic eruptions (since 1718) have caused over 1600 deaths and resulted in damage to property valued in excess of 4.8 million USD. In addition, current development plans for the area point towards increased risk of disastrous consequences from future activity at the volcano.All aspects of risk relevant to the volcano, are discussed, with particular emphasis on the manner in which these are perceived and on the question of acceptable risk. A method is presented for use in risk assessment of volcanic hazard and a number of risk zones are defined for the Soufriere volcano. Numerical estimates of the relative loss expected within each zone are obtained from a consideration of the value of property at risk, its vulnerability to the hazardous volcanic events and the expected spatial impact of volcanic events. Such estimates suggest that the northern-most third of the island is at least ten times more at risk than areas further south. The likelihood of death and destruction is extreme in such high risk areas, while the most feasible method of loss reduction is evacuation before an eruption occurs.Formerly at Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.     

Evaluation of aluminum speciation in surface waters in China and its environmental risk assessment

As the ongoing global research on acid precipitation is developing in depth, more and more attention has been paid to the ecological effects of aluminum (Al) due to its toxicity to plants and animals, which is caused by acid precipitation. As a very serious problem of terrestrial and aquatic environmental acidification occurs in China, especially in southwestern China, a systematic investigation of Al speciation in these regions is very important. In this paper, the Al speciation results of surface waters in China are reported and its ecological impacts is evaluated. More than 100 water samples were collected from about twenty provinces of China. Driscoll's Al speciation scheme combined with the modified MINQEL computer model is used for speciation of Al. This study shows that the ecological impacts of acidification are quite different between China and Western countries, because of different geographical environments and geological settings. In Western countries, acidification is mainly caused by NO₂^-. Due to low concentrations of K⁺, Na⁺, Ca²⁺, Mg²⁺, the buffer capacities of soil and water are weak. Therefore, natural waters can be acidified to pH<5 very easily, resulting in a considerable mobilization of Al and worsening of the ecological environment. In China, acid precipitation is mainly in the form of sulfuric acid. In northwestern China, concentrations of K⁺, Na⁺, Ca²⁺, Mg²⁺ are high in soil and surface waters. This leads to much higher capacity and a high resistance ability to acidification. The pH values of waters in this region are high (around 7) and no serious Al toxicity is found at present. However, in northeastern and southeastern China, the soil is rich in Al (unsaturated aluminosilicates in northeastern China, saturated aluminosilicates in north and central China, aluminum-rich soil in southeastern and southwestern China). The concentrations of K⁺, Na⁺, Ca²⁺, Mg²⁺ in soil and waters are lower than those of northwestern China. Therefore the buffer capacity is limited. Numerous surface waters have already been acidified and pH values declined to 5. The impacts of Al toxicity on ecological systems in these regions are very serious, especially in Jiangxi, Hubei Provinces and Chongqing Municipality.     

The inhibition of marine nitrification by ocean disposal of carbon dioxide

In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO2 from the flue gases of fossil fuel-fired power plants. The release of large amounts of CO2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8. In an effort to determine whether these CO2-induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique. For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH. Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca. 50% at pH 7 and more than 90% at pH 6.5. Nitrification was essentially completely inhibited at pH 6. These findings suggest that the disposal of CO2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate. It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected. However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur. Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena. Clearly, more research on the environmental effects of ocean disposal of CO2 is needed to determine whether the potential costs related to marine ecosystem disturbance and disruption can be justified in terms of the perceived benefits that may be achieved by temporarily delaying global warming.     

利用尾矿废石制造微晶玻璃花岗岩的投资可行性分析

在论述尾矿废石利用现状的基础上,对利用尾矿废石制造微晶玻璃花岗岩的投资可行性进行了分析,提供了一套可用于此类决策的分析方法。     

油气勘探开发项目投资决策路径的设计

研究油气勘探开发项目投资决策路径的根本目的在于规避风险,以利润极大化为原则,兼顾社会目标,正确选择投资方向,合理安排投资规模,保证石油化工企业油气资源的持续安全供应和可持续发展,提高集团的竞争力.油气勘探开发项目具有明显的实物期权特性,传统的NPV方法已经不适应此类项目的评价与决策,本文结合中石化的实际,从企业目标和社会目标2个方面着手,提出了基于实物期权的油气勘探开发项目投资决策路径,从而丰富了项目投资决策的思路和方法.