Study on Failure Mechanism and Bearing Capacity of Three-Dimensional Rectangular Footing Subjected to Combined Loading

This paper presents two kinematic failure mechanisms of threc-dimensional rectangular footing resting on homogeneous undrained clay foundation under uniaxial vertical loading and uniaxial moment loading. The failure mechanism under vertical loading comprises a plane strain Prandti-type mechanism over the central part of the longer side, and the size of the mechanism gradually reduces at the ends of the longer side and over the shorter side as the corner of rectangular footing is being approached where the direction of soil motion remains normal to each corresponding side respectively. The failure mechanism under moment loading comprises a plane strain scoop sliding mechanism over the central part of the longer side, and the radius of scoop sliding mechanism increases linearly at the ends of the longer side. On the basis of the kinematic failure mechanisms mentioned above, the vertical ultimate bearing capacity and the ultimate bearing capacity against moment or moment ultimate bearing capacity are obtained by use of upper bound limit analysis theory. At the same time, numerical analysis results, Skempton＇ s results and Salgado et al. ＇s results are compared with this upper bound solution. It shows that the presented failure mechanisms and plastic limit analysis predictions are validated. In order to investigate the behaviors of undrained clay foundation beneath the rectangular footing subjected to the combined loadings, numerical analysis is adopted by virtue of the general-purpose FEM software ABAQUS, where the clay is assumed to obey the Mohr-Coulomb yielding criterion. The failure envelope and the ultimate bearing capacity are achieved by the numerical analysis results with the varying aspect ratios from length L to breadth B of the rectangular footing. The failure mechanisms of rectangular footing which are subjected to the combined vertical loading V and horizontal loading H （Vertical loading V and moment loading M, and horizontal loading H and moment loading M respectively are observed in the finite e     

山东翟镇井田煤层风氧化特征及影响因素

该文通过对翟镇井田上组煤风氧化特征及发育规律的分析，找出了影响煤层风氧化为煤层上覆煤系地层厚度、煤层顶板岩性和煤层顶板岩石的裂隙发育程度等多方面因素，依此为翟镇井田上组煤的风氧化范围的预测提供了依据。     

顾及观测质量的多系统融合PPP三维凸包选星算法

从卫星空间构型出发，构建多系统融合PPP的三维凸包选星算法；为进一步改善多系统融合PPP的定位性能，提出顾及观测质量的三维凸包选星思路；最后结合实测数据验证并分析各自的选星效果和定位性能。     

Influence of partial confinement and Holocene river formation on groundwater flow and dissolution in the Florida carbonate platform

Much of what is known about groundwater circulation and geochemical evolution in carbonate platforms is based on platforms that are fully confined or unconfined. Much less is known about groundwater flow paths and geochemical evolution in partially confined platforms, particularly those supporting surface water. In north‐central Florida, sea level rise and a transition to a wetter climate during the Holocene formed rivers in unconfined portions of the Florida carbonate platform. Focusing on data from the Santa Fe River basin, we show river formation has led to important differences in the hydrological and geochemical evolution of the Santa Fe River basin relative to fully confined or unconfined platforms. Runoff from the siliciclastic confining layer drove river incision and created topographic relief, reorienting the termination of local and regional groundwater flow paths from the coast to the rivers in unconfined portions of the platform. The most chemically evolved groundwater occurs at the end of the longest and deepest flow paths, which discharge near the center of the platform because of incision of the Santa Fe River at the edge of the confining unit. This pattern of discharge of mineralized water differs from fully confined or unconfined platforms where discharge of the most mineralized water occurs at the coast. Mineralized water flowing into the Santa Fe River is diluted by less evolved water derived from shorter, shallower flow paths that discharge to the river downstream. Formation of rivers shortens flow path lengths, thereby decreasing groundwater residence times and allowing freshwater to discharge more quickly to the oceans in the newly formed rivers than in platforms that lack rivers. Similar dynamic changes to groundwater systems should be expected to occur in the future as climate change and sea level rise develop surface water on other carbonate platforms and low lying coastal aquifer systems. Copyright © 2012 John Wiley & Sons, Ltd.     

不确定性对象表达及其时空拓扑研究

不确定性对象时空拓扑关系研究的滞后,严重制约了时空推理与分析的进展。文中分析了时空对象空间信息与时间信息不确定性,并引入Rough集理论的上、下近似集概念对不确定性对象进行表达。另外,根据时空对象空间与时间信息的确定性与否,把时空对象归纳为4种类型,时空对象间的时空拓扑描述框架归纳为10种。再是,基于点集理论、Egenhofer的空间拓扑与舒红的时态拓扑关系研究成果,给出4-交扩展模型的时空拓扑描述框架,并得出类型I对象间的时空拓扑是最基本的拓扑关系,类型IV对象间的拓扑关系是最复杂的拓扑关系,其他类型对象间的时空拓扑都可通过类型对象I间的和类型对象IV间的时空拓扑演绎而得。最后,鉴于不确定性对象时空拓扑的复杂性,给出不确定性拓扑描述表达的流程体系。     

地球引力位球谐级数展开的收敛性研究(英文)

Given a continuous boundary value on the boundary of a "simply closed surface"S that encloses the whole Earth, a regular harmonic fictitious field V*(P) in the domain outside an inner sphere K i that lies inside the Earth could be determined, and it is proved that V*(P) coincides with the Earth’s real field V(P) in the whole domain outside the Earth. Since in the domain outside the inner sphere Ki and the fictitious regular harmonic function V*(P) could be expressed as a uniformly convergent spherical harm...     

Environmental Process and Convergence Belt of Atmospheric NO2 Pollution in North China

Both surface environmental monitoring and satellite remote sensing show that North China is one of the regions that are heavily polluted by NO2. Using the NO2 monitoring data from 18 major cities in the region, the tropospheric NO2 column density data from the Ozone Monitoring Instrument (OMI) on the Aura satellite, and the observations from the China Meteorological Administration network, this paper analyzes a regional NO2 pollution event in February 2007 over North China, examines the convergence of the pollutant, and identifies its correlation with the atmospheric background conditions. The results show that daily mean NO2 concentrations derived from surface observations are consistent with the mean values of the OMI measurements, with their correlation coefficient reaching 0.81. The correlations of NO2 concentration with general weather patterns and sequential changes of temperature structure from 925 hPa down to the surface indicate that the weather fronts, high pressure and low pressure systems in the atmosphere play a role in changing the temporal and spatial evolutions of NO2 through removing, accumulating or converging of the pollutant, respectively. It is also found that the eastern Taihang Mountains is most heavily polluted by NO2 in North China. Based on a model that correlates NO2 column density with surface wind vector, the relation of the NO2 concentrations in six major cities in North China to the surrounding wind field is analyzed. The results show that the maximum wind field is associated with the highest frequency of pollution events, and under certain large-scale atmospheric conditions together with the topographic effect, small- and meso-scale wind fields often act to transport and converge pollutants, and become a major factor in forming the heaviest NO2 pollution event in North China. Analysis of the causes for the severe NO2 pollution event in this study may shed light on understanding, forecasting, and mitigating occurrences of heavy NO2 pollution.     

山东济宁何岗煤矿下组煤水文地质条件研究

对济宁何岗煤矿16上、17煤水文地质条件进行补充勘探。研究认为济宁何岗煤矿井田内主要含水层有第四纪砂砾层,山西组3上、3下煤层顶底板砂岩、太原组三灰、十下灰、十三灰及奥陶纪灰岩。16上、17煤的主要水害是太原组下部灰岩水和奥灰水,16上、17煤水文地质条件属中等局部复杂类型,开采时的矿井最大涌水量为816m3／h。断层和裂隙是诱发突水的主要因素,生产中必须采取有效的安全防水措施。     

北羌塘盆地索瓦组上段的时代、古气候及石油地质特征

索瓦组上段是羌塘盆地演化晚期的一套潮坪—潟湖相沉积,分布于北羌塘盆地中部。通过对索瓦组上段区域地层对比,发现索瓦组上段在盆地东部、西部和南部的岩性变化较大,海相油页岩的出露地仅分布于北羌塘坳陷南部胜利河—长蛇山—托纳木一线的局限海湾—潟湖的边缘带,其形成明显受到了古地理条件的控制。根据索瓦组上段以及其下伏地层产出的生物化石组合,并结合油页岩的Re-Os同位素年龄,认为索瓦组上段的时代可能为早白垩世。对该组产出的孢粉化石组合和硅化木分析表明,索瓦组上段在沉积早期和晚期的古气候条件发生了明显的变化,早期为温暖和湿润气候,而晚期为半干旱—干旱气候,这种垂向上的古气候变化特征不仅仅局限于胜利河地区,可能在整个北羌塘盆地都普遍存在。索瓦组上段发育的油页岩及其上部膏岩沉积组合的发现,对于评价羌塘盆地演化晚期的石油地质条件具有重要的意义。