Probabilistic assessment of soil liquefaction considering spatial variability of CPT measurements     

Gökhan Saygili 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(2):197-207

The conventional liquefaction potential assessment methods (also known as simplified methods) profoundly rely on empirical correlations based on observations from case histories. A probabilistic framework is developed to incorporate uncertainties in the earthquake ground motion prediction, the cyclic resistance prediction, and the cyclic demand prediction. The results of a probabilistic seismic hazard assessment, site response analyses, and liquefaction potential analyses are convolved to derive a relationship for the annual probability and return period of liquefaction. The random field spatial model is employed to quantify the spatial uncertainty associated with the in-situ measurements of geotechnical material.  相似文献   

The need for judgement in geotechnical reliability studies     

J. Michael Duncan 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(1):70-74

ABSTRACT

A core principle of geotechnical engineering practice is the need to exercise judgement in evaluating soil and site conditions and in performing analyses. The requirement for considering judgement applies equally to performing deterministic or probabilistic analyses. In addition, for probabilistic analyses, choices must be made among the possible methods of analysis and the method of characterising variables. Consequently, geotechnical reliability studies inevitably involve significant uncertainties, and judgement is needed to perform reliability analyses and to evaluate the results. Two case histories, briefly described here, show that judgement and experience are essential prerequisites for meaningful assessment of geotechnical reliability.  相似文献   

固定式海洋平台结构风险设计方法综述     

李晓冬  唐文勇 《海洋工程》2017,35(1):147-156

海洋平台的结构设计中主要考虑海洋环境和工作荷载作用,但近年来事故荷载的影响日益引起设计者关注。在此背景下,以固定式导管架平台结构为目标,综述当前针对事故荷载的风险设计方法的应用现状。首先论述在事故极限状态设计中应用风险分析的必要性;随后综述通用规范,如NORSOK、DNV、API等规范系列中对风险分析方法的使用现状,包括风险决策的不同层次、安全标准的各类形式,重在分析各类规范相关规定的异同,探讨各类方法的适用性;最后结合我国现状,论述若针对事故荷载编制基于风险方法的设计规范,目前尚存的问题,以及解决途径。  相似文献   

琼州海峡海口站近岸风暴增水概率风险分析     

陈玲舫  韩树宗  车志伟  罗耀  谢强 《海洋工程》2017,35(2):115-122

基于海口站1976~1997年逐时潮位和逐日最大风速资料,利用阿基米德Copula函数构建海口年最大增水与相应日期最大风速的联合概率分布模型。结果表明:1)广义极值分布可作为海口站年最大增水和相应日期最大风速的边缘分布。两个序列之间存在强正相关关系,G-H Copula函数更适用于作为海口站年最大增水和相应日期的最大风速联合概率分布的连接函数。2)两变量联合作用的同频率增水高度设计值与增水的单变量边缘分布设计值之间的相对差值约为7.5%。3)条件概率1(P(Y≥y|X≥x))中同频率的年最大增水和相应风速的遭遇概率介于78.2%~80.9%,条件概率2(P(Y≥y|X≤x))中同频率的年最大增水和相应风速两者的遭遇概率小于4.8%。  相似文献   

Recognition of geochemical footprints of mineral systems in the regolith at regional to continental scales     

P. de Caritat  P. T. Main  E. C. Grunsky  A. W. Mann 《Australian Journal of Earth Sciences》2017,64(8):1033-1043

Understanding the character of Australia's extensive regolith cover is crucial to the continuing success of mineral exploration. We hypothesise that the regolith contains geochemical fingerprints of processes related to the development and preservation of mineral systems at a range of scales. We test this hypothesis by analysing the composition of surface sediments within greenfield regional-scale (southern Thomson Orogen) and continental-scale (Australia) study areas. In the southern Thomson Orogen area, the first principal component (PC1) derived in our study [Ca, Sr, Cu, Mg, Au and Mo at one end; rare earth elements (REEs) and Th at the other] is very similar to the empirical vector used by a local company (enrichment in Sr, Ca and Au concomitant with depletion in REEs) to successfully site exploration drill holes for Cu–Au mineralisation. Mapping of the spatial distribution of PC1 in the region reveals several areas of elevated values and possible mineralisation potential. One of the strongest targets in the PC1 map is located between Brewarrina and Bourke in northern New South Wales. Here, exploration drilling has intersected porphyry Cu–Au mineralisation with up to 1 wt% Cu, 0.1 g/t Au, and 717 ppm Zn. The analysis of a comparable geochemical dataset at the continental scale yields a compositionally similar PC1 (Ca, Sr, Mg, Cu, Au and Mo at one end; REEs and Th at the other) to that of the regional study. Mapping PC1 at the continental scale shows patterns that (1) are spatially compatible with the regional study and (2) reveal several geological regions of elevated values, possibly suggesting an enhanced potential for porphyry Cu–Au mineralisation. These include well-endowed mineral provinces such as the Curnamona and Capricorn regions, but also some greenfield regions such as the Albany-Fraser/western Eucla, western Murray and Eromanga geological regions. We conclude that the geochemical composition of Australia's regolith may hold critical information pertaining to mineralisation within/beneath it.  相似文献   

气候变化下珠江三角洲网河区洪潮耦合高水位的集中期特征及变异规律   总被引：1，自引：0，他引：1       下载免费PDF全文

唐亦汉  陈晓宏  邓攀攀 《水文》2017,37(3):42-47

气候变化环境下三角洲感潮河段洪潮耦合条件改变。除高水位量级外,其集中期特征与变化规律也是体现三角洲洪水情势变异的重要因素。采用圆形分布法计算得到珠江三角洲16站的高水位集中日、集中度、高峰期的起止时间等集中期特征,并分析其多年变化规律。结果发现:(1)是否考虑水位量级对于由圆形分布法计算得到的水位集中性没有显著影响;(2)珠三角入口与口门站点的高水位集中期比网河站长;(3)入口与网河站的集中日相近,口门站集中日最迟;珠三角大部分站点的高水位集中日有延后倾向,而发生时间趋于集中稳定;(4)入口及口门站点的集中日波动性都高于网河区站,且珠三角集中日波动性有随时间推进而减小的趋势。研究结果为三角洲洪水情势变异分析提供了新角度,为珠江三角洲的高水位采样、频率分析及重现期设计值计算提供数据基础,并为区域防洪减灾政策制定提供理论支持。  相似文献   

鲁西南聊考断裂带地震危险性评价与活动性分布     

刘方斌  曲均浩  田兆阳  刘承雨 《大地测量与地球动力学》2017,37(8):802-807

利用1970年以来沿聊考断裂带及周边50 km范围内的地震数据,结合历史强震与现今地震活动背景,分别运用最大似然法和最小二乘法对研究区进行b值计算,圈出高应力累积区,并借助时间相依的地震潜势概率评估方法以及地震活动性分布,得出以下结论：1）南段的范县、清丰、濮阳以及鄄城地区的b值维持在0.6～07之间,属于高应力积累区;2）未来50 a内南段危险性较高,100 a内整条断裂发生M5.0～6.0地震的可能性较大;3）地震活动主要集中在115.2°～115.6°E、34.9°～36°N区域内,且自2000年后地震活动性变强。  相似文献   

基于Bootstrap方法的岩土体参数联合分布模型识别     

唐小松  李典庆  周创兵  方国光 《岩土力学》2015,36(4):913-922

小样本容量岩土体参数最优联合概率分布模型的识别是一个富有挑战性的问题。基于Bootstrap提出了小样本容量岩土体参数最优边缘分布函数和最优Copula函数识别方法。简要介绍了岩土体参数联合概率分布函数构造的Copula方法,采用AIC准则识别最优的边缘分布函数和Copula函数。将识别结果表示为不同备选边缘分布函数和Copula函数为最优边缘分布和最优Copula的权重系数集合,以基桩荷载-位移双曲线参数试验数据为例证明了所提方法的有效性。结果表明：基于小样本容量岩土体参数试验数据估计的样本均值、标准差和相关系数具有较大的离散性,这种离散性进一步导致了统计量AIC值存在较大变异性。提出的基于Bootstrap的最优边缘分布函数和最优Copula函数识别方法不仅可以有效地考虑统计量AIC值的变异性,而且能够综合地反映不同备选边缘分布函数和Copula函数为最优边缘分布和最优Copula函数的概率,为小样本容量岩土体参数最优边缘分布函数和最优Copula函数的识别提供了一条有效的途径。  相似文献   

基于综合变异系数的地基承载力可靠性分析   总被引：2，自引：0，他引：2  

曹宇春  刘富玲 《岩土力学》2014,35(7):1950-1956

采用一次二阶矩法,考虑岩土参量变异系数的试验及历史数据,提出了基于综合变异系数的地基承载力简化可靠性与风险分析方法。利用提出的简化可靠性与风险分析方法,可在传统确定性分析的基础上,采用合理的变异系数,分别得到与地基承载力有关的可靠度、破坏概率和平均期望损失的最可能值及其变化范围,为提出优化的地基基础设计方案和工程决策奠定基础;相对于土重度和黏聚力,地基承载力可靠度对于内摩擦角的变化更加敏感;设计时可以综合考虑所需的安全系数、可靠度和破坏概率,确定合适的基础宽度或基底面积。当地基土的场地勘察统计结果的变异系数权重逐渐增加时,综合变异系数不断减小,其相应的地基承载力的可靠度逐渐增加,而相应的破坏概率逐渐减少。  相似文献   

基于模糊分类的UBGM(1,1)-Markov模型在露天矿边坡沉降预测中的应用     

马占武  何兵  鲁明星  徐振洋 《大地测量与地球动力学》2020,40(12):1259-1262

针对UBGM(1,1)-Markov模型中存在2个邻近值可能被归属到不同状态,导致预测值产生偏差的问题,结合模糊分类理论,构建基于模糊分类的无偏灰色-马尔科夫模型(unbiased gray-Markov model based on fuzzy classification, FC-UBGM(1,1)-Markov)。首先对UBGM(1,1)模型进行残差修正,然后将修正后拟合值的相对残差序列作为Markov链进行区间划分,再结合模糊分类的隶属度函数,计算相对残差的模糊向量,根据隶属度确定其所属的状态。实际算例表明,该模型比传统UBGM(1,1)-Markov模型的预测效果更好。  相似文献