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81.
Adnan A. Basma Samer A. Barakat Maher T. Omar 《Geotechnical and Geological Engineering》2003,21(3):225-242
The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and
the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This
is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this
case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing
design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order
Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length,
are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance
are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions
along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing
what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient
of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities
of the soil properties, the classical design technique produced a relatively high failure probability.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
82.
鄂豫皖交界地区地震地质背景与中强地震复发特征的研究 总被引:1,自引:2,他引:1
鄂豫皖交界地区位于东大别山西部,历史中强地震(M≥43/4)主要发生在土地岭-落儿岭及商城-麻城断裂带上,且“互动”和“连动”的特征较为显著。根据这一特征,在研究东大别山区域地质、地壳结构、断裂活动及地震构造应力场特征的基础上,可将鄂豫皖交界地区的中强地震作为秦岭-大别山活动地块中的次级地块的整体活动来看待。该区历史地震活动整体表现为丛集特征,而主要发震断层(土地岭-落儿岭断裂)的历史地震活动则具有相对较好的准周期性。地震复发周期研究提示,该地块近期发生M≥5.0左右地震的危险性较大,而霍山-六安地区为未来发生中强地震的主要危险区。 相似文献
83.
AnalysisandstudyofthelargeearthquakeriskinYanqingHuailaibasinCHANGQUANLIU(刘昌铨)SHIXUJIA(嘉世旭)MINGJUNLIU(刘明军)CHANGFALI(李长发... 相似文献
84.
85.
强震危险区预测是当前地震预报中的重要课题之一。笔者以预警活断层、预警活断层分段研究解决断层活动的时间和空间尺度为主线,配合地震活动动态分析、地震波介质特征早期信息、近场趋势性前兆异常和危险性概率预测,确定了判别几年尺度强震危险区的指标。在“八五”地震科技课题研究过程中,圈这了范围不超过10000km^2的5个强震危险区,已成功地对1993年10月2日若羌6.6级地震、1995年5月2日乌苏5.8级 相似文献
86.
叙述了浅层地下水资源评价中几个常用参数(给水度、降雨入渗补给系数和潜水蒸发系数)的测定和估计方法,并结合实例进行剖析.通过分析,得到几点新的认识:(1)给水度值同注水的方式有关,在实际情况中,由于农田表层土壤疏松,且有作物影响,因而其最大值会出现在地表附近;(2)用抽水试验法测定给水度,其值因孔而异;(3)降雨入渗补给系数与土壤结构和给水度的关系密切,一般随着埋深的增加,该系数随之减小;(4)不同季节和不同作物,潜水蒸发系数不同,表现在计算公式上的参数也不相同. 相似文献
87.
This paper examines historical and spatial trends in hazardous materials transportation spills from 1971 to 1991. While the number of spills Inc.reased steadily during the 1970s, peaking in 1978–1979, there has been a decline in frequency sInc.e then largely due to modifications in reporting. Monetary damages have the opposite temporal pattern, with major Inc.reases recorded from 1982 onward. Death and injury statistics are more variable. Spatially, accidents are more prevalent in the Rust Belt extending from the Northeast corridor westward to the Great Lakes states, as well as in the Southeast. The greatest potential risk to the public is found in smaller, more densely populated industrial states such as New Jersey, Delaware, and Maryland. The spatial distribution, however, has not changed. Potential risk sources (e.g., chemical industry, number of hazardous waste facilities, number of railroad miles) are the best predictors of hazmat Inc.ident frequency. Mitigation efforts (statewide regulatory and/or management policies) also help explain the variability in hazmat Inc.idents. 相似文献
88.
Hugo A. Loiciga 《The Professional geographer》1997,49(3):356-364
Runoff and precipitation scaling with respect to drainage area is analyzed for large river basins of the world, those with mean annual runoff in excess of 10 k3/yr. The usefulness of the specific runoff (runoff per unit drainage area, m/yr) to categorize runoff scaling laws across the complete spectrum of climatic and hydrologic conditions is evaluated. It is found that (1) runoff scales with drainage are in those river basins with specific runoff in excess of 0.15 m/yr (r2 = 0.88); (2) runoff scaling with drainage area shows remarkably high statistical correlation (r2= 0.97) in river basins with specific runoff equal to or larger than 1.0 m/yr; (3) runoff does not Inc.rease with Inc.reasing drainage area in river basins with specific runoff below 0.15 m/yr, where no discernible statistical association was found between runoff and drainage area; and (4) precipitation depth (m/yr) is inversely proportional to drainage area raised to a fractional exponent in river basins with specific runoff in excess of 0.15 m/yr. 相似文献
89.
LISA NAUGHTON-TREVES 《Geographical review》1997,87(1):27-46
ABSTRACT. Subsistence farmers near Kibale National Park, Uganda, fear and resent many wildlife species. In this article I compare records of crop damage by wildlife and livestock with local complaints about the worst animals and the most vulnerable crops. I discuss the concordance and discrepancies in complaints versus actual damage in light of physical parameters of risk and of social factors that shape perceptions and vulnerabilities. Crop losses were greatest at the edge of the forest, where immigrants are disproportionately represented. State proprietorship of wildlife amplifies local vulnerability and constrains traditional coping strategies, such as hunting. 相似文献
90.
Nuclear power plant siting provided the first significant public opportunity to examine nuclear safety and to affect nuclear policy. These discussions were prompted and fueled by perceptions of nuclear risk. Now, as we begin the process of nuclear decommissioning, we are finding that power plant removal—unsiting–is also likely to attract public interest. This paper presents a preliminary survey of how we are likely to react to this emerging theme, applying these findings within a land use context to see if it is likely to produce issues salient to the public. In so doing it also examines how these issues could affect decommissioning timing and type. It suggests that the most likely prospect is that power plants will remain on the landscape long after they are closed. 相似文献