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91.
本文以对营前特大桥桥位区的砂土液化的综合评判为例子,提出砂土液化必须运用定值准则的概念与方法并结合各种宏观液化势判定手段进行综合评判,文中还针对水下孔的水位取值进行了讨论。 相似文献
92.
Evaporation of perennial semi‐arid woodland in southeastern Australia is adapted for irregular but common dry periods 下载免费PDF全文
Measurements of water vapour flux from semi‐arid perennial woodland (mallee) were made for 3 years using eddy covariance instrumentation. There have been no previous long‐term, detailed measures of water use in this ecosystem. Latent energy flux (LE) on a half hourly basis was the measure of the combined soil and plant evaporation, ‘evapotranspiration’ (ELE) of the site. Aggregation over 3 years of the site measured rain (1136 mm) and the estimated evaporation (794 mm) suggests that 342 mm or 30% of rain had moved into or past the root zone of the vegetation. Above average rainfall during 2011 and the first quarter of 2012 (633 mm, 15 months) would likely have been the period during which significant groundwater recharge occurred. At times immediately after rainfall, ELE rates were the same or exceeded estimates of potential E calculated from a suitably parameterized Penman–Monteith (EPMo) equation. Apparent free water E from plant interception and soil evaporation was about 2.3 mm and lasted for 1.3 days following rainfall in summer, while in autumn, E was 5.1 mm that lasted over 5.4 days. The leaf area index (LAI) needed to adjust a wind function calibrated Penman equation (EPMe) to match the ELE values could be back calculated to generate seasonal change in LAI from 0.12 to 0.46 and compared well with normalized difference vegetation index; r = 0.38 and p = 0.0213* and LAI calculated from digital cover photography. The apparently conservative response of perennial vegetation evaporation to available water in these semi‐arid environments reinforces the conclusion that these ecosystems use this mechanism to survive the reasonably common dry periods. Plant response to soil water availability is primarily through gradual changes in leaf area. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
93.
一种以能量平衡为基础的干旱指数 总被引:5,自引:0,他引:5
本文以能量平衡公式为基础,根据实际蒸发与潜在蒸发的关系依赖于土壤水分含量的事实,导出一种表达干湿状况的指标——土壤水分干旱指数。 相似文献
94.
At the current rate of global warming, the target of limiting it within 2 degrees by the end of the century seems more and more unrealistic. Policymakers, businesses and organizations leading international negotiations urge the scientific community to provide realistic and accurate assessments of the possible consequences of so called “high end” climate scenarios.This study illustrates a novel procedure to assess the future flood risk in Europe under high levels of warming. It combines ensemble projections of extreme streamflow for the current century based on EURO-CORDEX RCP 8.5 climate scenarios with recent advances in European flood hazard mapping. Further novelties include a threshold-based evaluation of extreme event magnitude and frequency, an alternative method to removing bias in climate projections, the latest pan-European exposure maps, and an improved flood vulnerability estimation.Estimates of population affected and direct flood damages indicate that by the end of the century the socio-economic impact of river floods in Europe is projected to increase by an average 220% due to climate change only. When coherent socio-economic development pathways are included in the assessment, central estimates of population annually affected by floods range between 500,000 and 640,000 in 2050, and between 540,000 and 950,000 in 2080, as compared to 216,000 in the current climate. A larger range is foreseen in the annual flood damage, currently of 5.3 B€, which is projected to rise at 20–40 B€ in 2050 and 30–100 B€ in 2080, depending on the future economic growth. 相似文献
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Ahmed Murad 《中国地球化学学报》2010,29(2):152-156
The stable isotopes of oxygen and hydrogen have been implemented to assess the recharge mechanisms in an area in the UAE bounded to the northwestern part of the Gulf of Oman and the southeastern part of the Arabian Gulf. The conversion of stable isotopes to deuterium excess was utilized as a supportive tool to understand the process of groundwater recharge. The concluding results of this study showed that the origin of moisture is the Mediterranean Sea. The precipitation is the main source of recharge, in which the precipitation having undergone evaporation before recharge occurs. The comparison between regression line for data collected in 1996 and regression line for samples collected in 2006 suggests that the precipitation water which recharged the groundwater, was diluted with groundwater and this dilution is observed from decreasing of the deuterium excess of collected groundwater samples with increasing isotopes of oxygen. The dilution of groundwater with the recharge water suggests modern-day recharge as it is seen from high deuterium excess that exceeded the deuterium excess of LMWL and was close to MMWL. 相似文献
98.
Zabuye Salt Lake in Tibet, China is a carbonate-type salt lake, which has some unique characteristics that make it different from other types of salt lakes. The lake is at the latter period in its evolution and contains liquid and solid resources. Its brine is rich in Li, B, K and other useful minor elements that are of great economic value. We studied the concentration behavior of these elements and the crystallization paths of salts during isothermal evaporation of brine at 15°C and 25°C. The crystallization sequence of the primary salts from the brine at 25°C is halite (NaCl) → aphthitalite (3K2SO4·Na2SO4) → zabuyelite (Li2CO3)→ trona (Na2CO3·NaHCO3·2H2O) → thermonatrite (Na2CO3·H2O) → sylvite (KCl), while the sequence is halite (NaCl) → sylvite (KCl) → trona (Na2CO3·NaHCO3·2H2O) → zabuyelite (Li2CO3) → thermonatrite (Na2CO3·H2O) → aphthitalite (3K2SO4·Na2SO4) at 15°C. They are in accordance with the metastable phase diagram of the Na+, K+-Cl?, CO32?, SO42?-H2O quinary system at 25°C, except for Na2CO3·7H2O which is replaced by trona and thermonatrite. In the 25°C experiment, zabuyelite (Li2CO3) was precipitated in the early stage because Li2CO3 is supersaturated in the brine at 25°C, in contrast with that at 15°C, it precipitated in the later stage. Potash was precipitated in the middle and late stages in both experiments, while boron was concentrated in the early and middle stages and precipitated in the late stage. 相似文献
99.
极震区岩体地震动力破坏是造成极震区严重的地震地质灾害和次生灾害的根本原因。汶川地震中因此而导致的交通工程结构损坏、中断和次生崩滑流、堰塞湖等地质灾害,不仅加剧了灾害损失,并给震后的灾区恢复重建和对外交通遗留了较多的安全隐患。从岩体稳定、山体稳定和区域稳定的层次,分别对有关极震区岩体地震动力破坏的主要研究成果进行了系统总结,分析了其现状和存在的问题。结合对研究思路和方法论的讨论,构建了极震区岩体地震动力破坏研究的体系框架,提出了极震区岩体地震动力破坏研究的主要内容和方向,以期明晰概念,理清思路,为有关问题的深入研究提供有益的参考。 相似文献
100.
库车坳陷以产天然气为主,同时产出少量原油和凝析油,油气充注不同步,普遍具有"油早气晚"的特点,晚期大量天然气的侵入,必然对早期聚集的油藏发生改造作用。对气藏中原油成分变化的定量计算和讨论,可为天然气的注入强度定量评价提供直接证据。未遭受气洗的原油,正构烷烃摩尔浓度的对数与相应的碳数呈线性关系,而气洗作用可使轻组分的正构烷烃最先溶解于干气中,并随着天然气继续向前运移,原始油藏中的轻组分正构烷烃大大减少。以此为理论基础,建立了正构烷烃损失的定量计算模型。结果表明克拉2构造原油正构烷烃损失程度最高,平均可达70%左右,大北构造带原油正构烷烃损失程度差异较大,与该地区断块发育有关。气洗作用导致原油正构烷烃减少,而金刚烷、多环芳烃等在天然气中溶解度较低的化合物得以浓缩富集,相对含量大大增加。轻芳烃含量也会随之而增加,原油芳香度增加,石蜡度降低。在模拟实验基础上对气洗程度进行了定量评价,初步估算表明,克拉2构造原油遭受的气洗作用最强,是其他构造带的2~5倍。 相似文献