黄土边坡可靠度的随机有限元分析     

李萍  白健忠  GRIFFITHS D V  李同录  郑亚楠 《地球科学与环境学报》2019,(1):116-126

为了研究黄土边坡的可靠度,在对黄土强度参数进行变异性统计、概率分布检验及垂直向自相关距离计算的基础上,将黄土强度参数黏聚力和内摩擦角作为随机变量,将其在二维边坡剖面的空间变化作为随机场,用局部平均细分法将符合一定均值和标准差的强度参数按随机场分布在边坡剖面的有限元网格上,再采用弹-理想塑性有限元计算边坡稳定系数,用MonteCarlo法计算其失效概率。结果表明:黄土黏聚力的变异系数多在0.30以上,内摩擦角的变异系数多在0.20以下,且黄土高原从西向东两个参数的变异性都增大;黏聚力和内摩擦角的概率分布类型对边坡失效概率计算结果影响显著,统计检验发现黏聚力采用对数正态分布、内摩擦角采用正态分布为宜;黄土地层的垂直向自相关距离多在0.7m以内,与计算厚度的比值多小于0.2;在大部分黄土的变异系数与自相关距离水平下,采用确定场进行可靠度分析,多数情况将极大地高估了黄土边坡的失效概率,而在极端高变异系数水平下,采用确定场进行可靠度分析,又将极大地低估其失效概率。  相似文献   

Palaeodiet of Miocene Producers and Depositional Environments: Inferences from the First Evidence of Microcoprolites from India     

Vivesh V. KAPUR  Kamlesh KUMAR  P. MORTHEKAI  Amritpal Singh CHADDHA 《《地质学报》英文版》2020,94(5):1574-1590

This paper reviews research on coprolites from India, providing the first evidence of microcoprolites from the early Miocene (Aquitanian) Khari Nadi Formation sedimentary succession, exposed about 1.5 km northeast of the village of Kotada, Kachchh (Kutch) District, Gujarat State, western India. Morphometric and size comparisons (in a statistical framework) with known coprolites from the Mesozoic-Cenozoic successions of India (including those recorded herein) and globally suggest that fishes were the likely producers of the Kotada coprolites. Scanning electron microscopy confirms the presence of fish dental remains within the coprolites, while both Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) reveal the phosphatic nature of the microscopic coprolite specimens (recorded herein) hinting that the producer(s) were predominantly carnivorous (ichthyophagous) in their diet. Furthermore, X-Ray Fluorescence (XRF) analysis of the host and associated lithologies allows us to deduce that the Kotada coprolites were deposited in a shallow marine environment, with possible aerial exposure of the host lithology occurring at some point after deposition. To the best of our knowledge, the present report is the first record of microscopic fish coprolites from India, as well as being the first from the Aquitanian of India and the oldest Neogene record from India.  相似文献   

Assessment of sediment connectivity using modelling and field-based approaches in the Slaví? River catchment(Moravskoslezské Beskydy Mts,Czech Republic)     

MACUROVá Tereza  ?KARPICH Václav 《山地科学学报》2024,(3):734-753

Mountain streams act as conveyors of sediments within the river continuum, where the physical transport of sediments between river reaches through the catchment or between individual parts(e.g., between hillslopes and channels) of the catchment is assumed. This study focused on sediment connectivity analysis in the Slaví? River catchment in the Moravskoslezské Beskydy Mts in the eastern part of the Czech Republic. The connectivity index and connectivity index target modelling were combined with ...  相似文献   

Responses of a Northern Adriatic Ampelisca-Corbula community to seasonality and short-term hydrological changes in the Po river     

N'siala GM  Grandi V  Iotti M  Montanari G  Prevedelli D  Simonini R 《Marine environmental research》2008,66(4):466-476

During the 20th century, increased nutrient inflow has increased the frequency and intensity of eutrophication events in the North-western Adriatic Sea. More recently, evidence of a reduction in the Po river flow and a recovery of the benthic environment were reported. We examined the role played by Po river regime and seasonality in determining the temporal pattern of macrozoobenthos variation: samples were collected from a site located 10-12km off Cesenatico during two years from October 2004 to September 2006, when the mean Po discharge remained exceptionally low. 88 taxa were found, and the community was dominated by few species: Ampelisca diadema, Lumbrineris latreillii, Corbula gibba, Aricidea claudiae, Levinsenia gracilis and Nucula nucleus account for about 80% of total abundances. The density of these species exhibited a marked seasonal variability. Moreover, the total abundance and the density of the sensitive species, A. diadema, were negatively affected by several disturbance events (hypoxic conditions, frequent storms and an anomalous winter flood) that occurred between November 2005 and March 2006. The reduction of C. gibba and the increase of A. diadema densities observed in the investigated period, and verified recently by other authors could be related to the reduction in river inputs as a consequence of climatic changes.  相似文献   

Cloning and mRNA expression analysis of an ABCG2 (BCRP) efflux transporter in rainbow trout (Oncorhynchus mykiss) liver and primary hepatocytes     

Zaja R  Munić V  Smital T 《Marine environmental research》2008,66(1):77-79

  相似文献   

Palynoflora of Wulaga dinosaur site in Jiayin （ Zeya-Bureya Basin,China）     

V.S. Markevich  E.V. Bugdaeva 《东北亚地学研究》2009,(3):117-121

The palynological assemblage from Wulaga dinosaur site in Jiayin from southeastern Zeya-Bureya Basin was studied. The high content of pteridophytes spores is characteristic for this assemblage. The further characters are in decrease of abundance-tricolpate pollen, Ginkgocycadophytus, pollen of Taxodiaceae, Cupressaceae and Taxaceae （TCT） , bisaccate pollen of Pinaceae, and triporate pollen. The bone-bearing burials of Wulaga dinosaur site formed under conditions of vast swampy river valley covered by ferns and taxodialeans. Tricolpate pollen, produced by plants, close to those of Platanaceae, Fagaceae, Betulaceae, and Juglandaceae, counts in favor of valley river open canopy forests.  相似文献   

碎屑流动力学-环境流体的影响     

Hedda  Breien  Matteo  Pagliardi  Anders  Elverhoi  Fabio  V.  De  Blasio  杨丽娟 《海洋地质》2009,(1)

为阐明重力滑坡的基本原理,我们重点研究了环境流体是如何对碎屑流的特性加以影响的。为了达到这个目的,我们完成了一组不同的实验室测试,这组测试无论是从大气到水的外部环境还是从颗粒状到粘塑性物质的沉积物组分都是不同的。野外观察表明,水下重力流似乎比陆地上的重力流更易流动,例如,坡度小于1°的平缓陆坡上的水下滑坡向下滑动了非常远的距离。  相似文献   

基于岩石声发射实验结果探讨地震活动状态变化的预测意义   总被引：1，自引：0，他引：1  

李志雄  陶本藻  A.V.Ponomarev 《地震》2007,27(3):10-19

根据室内岩石破裂实验声发射结果, 论证了地震非均匀度参数(GL值)在识别声发射活动状态变化的有效性, 同时也考察了状态变化参量计算结果的稳定性。 在此基础上, 借用前苏联地震学家Mjachkin等提出的地震孕育至发生的雪崩不稳定裂隙形成模式, 探讨了部分强地震孕育过程中, 区域地震活动由无序到有序状态变化的可能形成机理。 利用地震状态参数, 即地震非均匀度(GL值)尝试开展了对我国未来一个时期地震大形势的定量分析预测。  相似文献   

Fluidizate-Explosive Occurrences in Ophiolites as Indicator of the Subduction Zone Activity: The Urals Example          下载免费PDF全文

V.R. SHMELEV 《《地质学报》英文版》2017,91(Z1):36-38

  相似文献   

A Giant Gold System, Geita Greenstone Belt, Tanzania          下载免费PDF全文

I. V. SANISLAV  P. H. G. M. DIRKS  Y. A. COOK  T. G. BLENKINSOP  S. L. KOLLING 《地质学报》2014,88(Z2):110-111

Please refer to the attachment(s) for more details.  相似文献