条形基础极限承载力数值分析

根据塑性力学滑移线理论,推导了条形地基在极限平衡状态下的平衡微分方程,然后利用有限差分法推出地基土在极限状态时的有限差分公式,结合边界条件编制出地基承载力计算程序,该程序求解条形地基极限状态下的滑移线区域及相应的地基极限承载力值时可以考虑基础埋深、地基土重度、土的内摩擦角、基础与地基摩擦等参数。利用程序,得到了土的内摩擦角与地基承载力系数N? 的对应表,并全面讨论了基础埋深、地基土重度、内摩擦角及基础与地基摩擦角等参数对地基承载力和滑移线形状的影响,得到了一些有意义的结论。     

统一强度理论在地基承载力确定中的应用研究

基于统一强度理论,考虑中间主应力对地基承载力的影响,给出了静止侧压力系数 条件下的地基临塑与临界荷载公式。结合实例,对基于统一强度理论和Mohr-Coulomb准则的地基承载力计算结果进行了对比分析。新的理论公式更为确切地反映了地基承载力的实质,有利于地基土体强度的充分发挥。基于河北境内177组不同土质地基的土性指标及载荷试验资料的统计分析,对中间主应力系数b的取值进行了深入细致的探讨,研究表明,对于粉土及黏性土地基,b的取值范围在0～0.5之间变化,理论计算所得地基承载力特征值与载荷试验实测值间的相对误差一般不超过5%     

地基弹塑性承载力安全性研究

随着对地基承载力理论研究的深入及大量工程实践的开展,暴露出弹性理论的诸多缺陷。基于弹-塑性理论,对以前学者的地基分类进行改进,推导出地基的临塑承载力、弹-塑性承载力以及极限承载力的公式,并且为了更好地进行地基土处于非线性变形阶段弹-塑性承载力的计算,提出了弹-塑性承载力利用率的概念;针对以前学者提出的危险度的概念,由于其不能在工程实际工程中很好地推广应用的缺点,给出了具有工程意义的弹-塑性承载力安全度Kep这一参数。结合工程实际说明只要Kep满足要求,地基土可用到非线性变形阶段,由此理论设计地基基础,造价将大大降低。     

方形和圆形基础地基极限承载力分析

通过对方形和圆形基础地基极限承载力的经验公式、理论解、静载荷试验结果进行对比分析,得到下列结论：对于砂性土,经验公式和理论解的计算结果明显偏小;对于粘性土,Vesic经验公式的计算结果更接近静载荷试验结果;李伟理论解适合于软粘性土,而周中理论解适合于高强度的粘性土。     

基于迈耶霍夫和汉纳冲剪理论计算地基极限承载力的研究

对迈耶霍夫和汉纳公式计算成层土地基承载力的步骤细化,推导出计算承载力的一般计算模式;运用现场载荷试验结果对计算成层土地基承载力的迈耶霍夫和汉纳公式进行验证,同时对迈耶霍夫和汉纳公式进行适当的修正。计算结果表明,成层土的迈耶霍夫和汉纳计算公式计算步骤的关键在于确定破坏面的极限深度,极限深度的判断对其计算的结果有重要影响。根据大型荷载板现场试验的结果,当土层超过两层时的成层土地基的极限承载力按迈耶霍夫和汉纳理论公式进行计算,其计算结果与实测值基本吻合。     

成层地基中单桩竖向承载力鲁棒性设计

城市建设中桩基应用广泛,单桩竖向承载力的计算方法及可靠性越来越受到设计人员重视。针对桩基设计中岩土参数的不确定性及桩基穿越成层地基对桩身承载力的影响问题,提出基于可靠度理论的鲁棒性设计方法。利用岩土参数变异性的平均值及标准差充分考虑岩土参数的不确定性,并通过扩大考虑地基土的不确定因素将单桩竖向承载力鲁棒性设计由砂土推广到黏土等一般性土壤;提出采用分层计算桩侧摩阻力作为不确定因素考虑地基土成层分布问题,按照承载力极限状态与正常使用极限状态作为目标函数进行桩基竖向承载力设计。单桩承载力鲁棒性设计将鲁棒性作为安全性评价标准,来评估桩基设计方案的可行性,以鲁棒性与经济性为优化目标对桩基设计进行多目标优化,设计方案在满足桩基承载力要求的同时,保证了桩基设计方案的鲁棒性与经济性。     

基于上限法的地基极限承载力计算模式探讨

当前地基极限承载力理论研究及实践应用的基本框架,仍采用的是Terzaghi所建议的三项叠加法,即分别考虑土体粘聚力、超载和地基土重对承载力的贡献,然后将三项进行叠加,由于土体并非线弹性材料,应用叠加原理在理论上是欠妥的。从理论上讲,采用整体考虑影响承载力的各种因素直接进行极限承载力计算更为恰当。为探讨采用三项叠加法与整体考虑各种影响因素直接计算的差别,基于多块体上限方法,分别采用两种计算方法对中心荷载作用下粗糙及光滑基础地基极限承载力问题进行了计算,探讨两种计算方法的差异,并从地基破坏面所反映出的信息揭示了两种计算存在差异的内在原因。     

港口工程中非均质层状地基承载力计算方法

在深水码头、防浪堤等大型港口工程建设中常常会遇到构筑物下覆地基由非均质的层状土构成的情况。对于这类非均质层状地基,我国港口工程地基规范推荐采用Hansen 61公式、Hansen 69公式和Sokolovskii数值解法3种方法计算地基的极限承载能力。然而,工程实践中由这3种方法计算得出的地基极限承载力数值往往有较大的差别。考虑到规范的继承性,基于牛顿迭代法,针对3个理论计算公式编制了计算程序,根据长江口深水治理二期工程地质实测资料,运用该计算程序对该地区地基的极限承载能力进行了计算比较。计算结果表明,对于非均质层状地基,在相同地质条件、相同荷载条件下Sokolovskii数值解法得到的承载力数值最大,Hansen 69公式得到的承载力数值最小。     

圆形基础地基极限承载力计算

利用临界滑动场法计算了浅埋圆形基础的地基承载力,并提供了系数N、Nq和Nc的计算表格和曲线,同时分析了侧面土压力对N、Nq的影响。通过建立土体条块极限平衡方程,推导了计算地基承载力的递推关系式。首先,设定土体计算范围,并划分条块和设置状态点; 其次,根据递推公式和推力极值原理计算各个状态点的参数,并搜索临界滑面; 最后,根据搜索出的临界滑面计算地基承载力。通过与已有系数计算值或模型试验的比较,验证了该方法的合理性。研究结果表明:N、Nq和Nc与其他学者的计算值相近; 相同情况下侧面土压力越大系数N、Nq越小。该方法是临界滑动场法在地基承载力研究中的推广应用,原理简单、易于编程,可为深入研究圆形基础地基承载力的计算提供参考。     

基于统一强度理论的地基极限承载力公式

现有的地基临塑荷载及极限承载力公式均以Mohr-Coulomb强度理论为基础建立的,没有考虑中间主应力的效应,其计算结果一般偏小,没有充分发挥土体强度潜能。基于统一强度理论考虑中间主应力的影响,以Terzaghi公式的假设与原理为基础,导出地基极限承载力公式的一般形式,太沙基地基极限承载力公式是其特例。由于考虑中间主应力的影响,计算的地基承载力比太沙基地基极限承载力要大,可发挥土体的强度潜能,得到一系列的解答。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Late Wuchiapingian (Late Dzhulfian,early Late Permian) limestone olistolites within the Tertiary flysch of Glypia Unit (Mount Parnon,central–eastern Peloponnesus,Greece)

Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931.     

PALEONTOLOGY

正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)     

GEOCHEMICAL EXPLORATION

正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.)     

MICROPALAEONTOLOGY

正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.)     

PETROLOGY

正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus.,     

ENVIRONMENTAL GEOLOGY

正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an     

PROSPECTING EXPLORATION

正20141266Fan Chaoyan(Guangdong Provincial Key Laboratory of Mineral Resources and Geological Processes,Guangzhou 510275,China);Wang Zhenghai On Error Analysis and Correction Method of Measured Strata Section with Wire Projection Method(Journal of