巴东长江公路大桥桥位边坡稳定可靠性研究

以巴东长江公路大桥桥位边坡为例，在前人稳定性评价的基础上，建立了基于剩余推力法和Sarma法的边坡稳定可靠性分析模型，分析表明边坡系统可靠性指标(β，Pf)能更准确地表达边坡稳定性、安全性和工程风险水平。     

A TEM and EELS study of carbon in a melt fragment from the Gardnos impact structure

A carbon‐rich melt fragment from the Gardnos impact structure has been studied for a better understanding of the preservation and structural form(s) of carbon that have been processed by impact melting. The carbon was analyzed in situ in its original petrographic context within the melt fragment, using high‐resolution techniques including focused ion beam‐transmission electron microscopy and electron energy loss spectroscopy. Results show that the carbon is largely uniform and has a nanocrystalline grain size. The Gardnos carbon has a graphitic structure but with a large c/a ratio indicating disorder. The disorder could be a result of rapid heating to high temperatures during impact, followed by rapid cooling, with not enough time to crystallize into highly ordered graphite. However, temperature distribution during impact is extremely heterogenous, and the disordered Gardnos carbon could also represent material that avoided extreme temperatures, and thus, it was preserved. Understanding the structure of carbon during terrestrial impacts is important to help determine if the history of carbon within extraterrestrial samples is impact related. Furthermore, the degree of preservation of carbon during impact is key for locating and detecting organic compounds in extraterrestrial samples. This example from Gardnos, together with previous studies, shows that not all carbon is lost to oxidation during impact but that impact melting can encapsulate and preserve carbon where it is available.     

Study on General Performance of Jack-up Under Elevated Condition

Method of checking for jack-up elevated performance including leg structure strength, fixation system or jacking system bearing capacity, pre-load requirements, spud can bearing capacity and overturning stability is suggested in this paper. As an example, a jack-up with truss legs is analyzed by finite element analysis method. This paper may be helpful to the rig owners, operators and designers.     

地震预报实验场:科学问题与科学目标

本文简要回顾了以往地震预报实验场的经验教训,讨论了新一代地震预报实验场的实施策略。汲取汶川地震的经验启示,本文提出"地震博弈"策略,即考虑中长期地震预测的可用性与不确定性,在监测与实验系统设计中考虑地震活动和地震构造相依的区域模型。对于特定的活动断裂或活动地块边界带的潜在强震段落,设置适应多种孕震模型的"想定地震破裂",针对地震孕育的"想定模式"设计观测项目和监测系统。这一系统以地震成因和孕震模型的有效约束、"预期"前兆的有效监测、预测/预报效能的有效检验为导向。从技术角度,本文提出将地震预报实验场作为一个"大科学工程",强调复杂的多层次、多组分技术系统性能的稳健性,以及为确保与地震有效的"近距离接触"的系统可持续性。     

苏北溱潼凹陷戴南组二段成岩作用与次生孔隙预测

成岩作用研究表明,戴南组二段成岩作用类型主要有机械压实、胶结、交代、溶解、粘土矿物充填等,并进行了各成岩作用对孔隙改造规模的统计。成岩作用阶段的划分,采纳了中华人民共和国石油天然气行业标准,将戴南组二段划分为早成岩Ｂ期和晚成岩Ａ期两个阶段。次生孔隙的发育、分布与泥岩压实曲线的紧密压实、大量脱水阶段或有机质的成熟阶段、生油门限以及混层粘土的第一迅速转化带有着密切联系,从而成为次生孔隙预测的着眼点。     

Analytic Solution of Elasto-Plastic Stress in Infinite Slope under Uniform Load

-According to the Mohr-Coulomb yield criterion,the stress field of the infinite slope is derivedunder a vertical uniform load q on the top of the slope.It is indicated that elastic and elasto-plastic stateswould occur in the slope.When q is smaller than the critical load,q_p,the slope is in the elastic state.Ifq equals q_p,the slope is in the critical state,and the plastic deformation would occur along the critical an-gle.With the increase of q,the plastic zone would extend,and the slope is in the elasto-plastic state.Ifq equals limit load,the slope is in the limit equilibrium state.The slope may be divided into three zones.Some charts of the critical angle,the critical and limit load coefficients are presented in this paper.     

Northern Eurasia earth science partnership initiative (NEESPI), science plan overview

Northern Eurasia Earth System Partnership Initiative, NEESPI, was established to address the global change processes associated with and/or originated within Northern Eurasia as well as to study the major socially-important processes within the region. NEESPI began as a US–Russian initiative but has quickly broadened into a fully international program. Scientists from 11 countries participated in preparing the NEESPI Science Plan. Current version of the Science Plan was released for public review on the World Wide Web in summer 2004 and finalized in December 2004. This paper provides an Overview of the Plan and is based, mainly, on its Executive Summary. The Overview describes the Plan's science themes and key science questions, provides a justification of the urgency studying Northern Eurasia from the global change prospective, and outlines research strategy and tools to address NEESPI science questions, as well as projected deliverables of the Initiative.     

Karst morphology and groundwater vulnerability of high alpine karst plateaus

High alpine karst plateaus are recharge areas for major drinking water resources in the Alps and many other regions. Well-established methods for the vulnerability mapping of groundwater to contamination have not been applied to such areas yet. The paper characterises this karst type and shows that two common vulnerability assessment methods (COP and PI) classify most of the areas with high vulnerability classes. In the test site on the Hochschwab plateau (Northern Calcareous Alps, Austria), overlying layers are mostly absent, not protective or even enhance point recharge, where they have aquiclude character. The COP method classifies 82% of the area as highly or extremely vulnerable. The resulting maps are reasonable, but do not differentiate vulnerabilities to the extent that the results can be used for protective measures. An extension for the upper end of the vulnerability scale is presented that allows identifying ultra vulnerable areas. The proposed enhancement of the conventional approach points out that infiltration conditions are of key importance for vulnerability. The method accounts for karst genetical and hydrologic processes using qualitative and quantitative properties of karst depressions and sinking streams including parameters calculated from digital elevations models. The method is tested on the Hochschwab plateau where 1.7% of the area is delineated as ultra vulnerable. This differentiation could not be reached by the COP and PI methods. The resulting vulnerability map highlights spots of maximum vulnerability and the combination with a hazard map enables protective measures for a manageable area and number of sites.     

REMOTE SENSING OF THE SEASONAL VARIATION IN COLUMN ABUNDANCE OF ATMOSPHERIC CH_4

Infrared solar spectra on clear days were measured automatically by an infrared solarspectrometer(ISS)with 0.4 cm~(-1) resolution developed by us.A line-by line(LBL)computationmethod was used to calculate theoretical atmospheric absorption.In the wavelength range of 3.410—3.438 μm.the absorption is mainly due to atmospheric methane and water vapor.Columnatmospheric methane was retrieved from the recorded infrared solar spectra.The seasonal variationof column atmospheric methane in Hefei has been obtained from the measuremental data of nearly18 months since the April of 1997.and found that it is similar to that of background data.Theinstruments.principles of measurement and some of results were introduced,and the results arealso discussed briefly in the paper.     

Factors controlling carbonate dissolution rates quantified in a field test in the Austrian alps

Carbonate dissolution rates were investigated by measuring the mass difference of carbonate tablets exposed to natural dissolution for 1 year. 70 tablets were distributed over 13 test sites on the north slope of the Hochschwab Massif in the Austrian Alps. The influences of altitude, subsoil vs. sub-aerial exposure, vegetation, karst morphology, soil humidity, sample lithology, and sample surface morphology were investigated. The observed dissolution rates varied between 13 and 40 μm/a for subcutaneous samples and about 11 μm/a for sub-aerial exposure. Outstandingly high rates of 48 μm/a were observed in a doline and nearly zero rates were measured at a site influenced by seeping spring water.A mass balance, using high-resolution hydrological data, was calculated for the Kläffer Spring, which has an average outflow of 4.8 m³/s. It indicated a loss of 21×10⁶ kg of carbonate rock per year which gives an average dissolution rate of 95 μm/a for the catchment area of 83 km². The dissolution rates of 10 μm/a from the sub-aerially exposed samples are comparable to values from limestone pedestals, which were protected from dissolution by glacial erratics for the past 15 ka.