Nonlinear dynamic finite element simulation of Alibey earth dam

In this study, dynamic behavior and earthquake resistance of Alibey earth dam was investigated. The dam was modeled with four node plane-strain finite elements (FE) and displacement-pore pressure coupled FE analyses were performed. Nonlinear material models such as pressure dependent and independent multi yield materials were implemented during the analyses. Transient dynamic FE analyses were performed with Newmark method. The Newton-Raphson solution scheme was adopted to solve the equations. Liquefaction and/or cyclic mobility effects were considered during the analysis. For the FE analyses, OpenSees (Open System for Earthquake Engineering Simulation) framework was adopted.     

Evaluation of the Risk of Marine Slope Instability: A Pseudo-3D Approach for Application to Large Areas

This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.     

滑坡稳定性分析与安全系数取值研究

在地质灾害中,滑坡灾害分布最广、发生频率最高、危害最大,是我国地质灾害防治的主要对象。滑坡研究的主要任务之一是稳定性分析。论文针对三板溪水电站进水口滑坡和水布垭水电站大岩淌滑坡,分别采用刚体极限平衡法、块体单元法、有限单元法对稳定安全系数和条间推力分布曲线进行分析和比较,研究各种方法的差异和计算精度,以及各种方法稳定安全系数的取值标准,希望为水利水电工程边坡设计规范有关有限单元法、块体单元法条目的编写和相应的允许安全系数取值标准的制定提供一定的参考。研究结果表明:①块体单元法计算的安全系数与刚体极限平衡法计算的安全系数可以采用相同的取值标准,而有限单元法计算的安全系数取值标准可适当降低;②块体单元法计算的条间水平推力、条间剪切力与刚体极限平衡法(尤其是Sarma法)计算的条间水平推力、条间剪切力非常相近,有限单元法计算的条间水平推力、条间剪切力较小;③分析方法、力学模型与参数取值应与安全系数取值标准相匹配。     

中国大陆科学钻探工程主孔（734～933m）榴辉岩和片麻岩元素及Sr-Nd同位素地球化学研究

对中国大陆科学钻探工程主孔两段榴辉岩与片麻岩互层的岩芯样品(Ⅰ:734.21-737.16m和Ⅱ:929.67-932.86m)分别进行了主要元素和微量元素以及Sr-Nd同位素分析。结果表明:(1)榴辉岩具有较大的成分变化范围(SiO2含量为46.8%-59.8%),表现出平坦或轻稀土(LREE)富集的分布模式和大离子亲石元素(LILE)富集或亏损以及Nb、Ta负异常特征。部分榴辉岩样品具有明显低的活动性元素(Rb、Ba和K)含量,指示了板块俯冲过程中的脱水变质效应;(2)两段岩芯中的片麻岩具有明显不同的主量和微量元素组成,其中第Ⅰ段具有相对较低的SiO2含量(61.3%～66.2%)和高的重稀土(HREE)含量,而第Ⅱ段具有明显偏高的SiO2含量(73.8%～74.1%)和低的HREE含量。但两段均表现出LREE富集和Eu负异常以及LILE富集和高场强元素(Nb、Ta、Ti)负异常特征;(3)榴辉岩和第Ⅰ段岩芯中的片麻岩具有相近的且偏高的εNd(750Ma)值(-3.6- 0.5),而第Ⅱ段岩芯中的片麻岩具有明显偏低的εNd(750Ma)值(-8.7)。部分片麻岩样品表现出较高的87Sr/86Sr比值(0.7070)和非常低的Rb/Sr比值(0.008),指示岩石Rb-Sr同位素体系受到了变质扰动。非活动性元素如Zr、Hf、Nb、Ta、Ti、Y、REE和Ti在脱水变质过程中没有受到明显扰动,因此可用于恢复榴辉岩和片麻岩的原岩性质及其形成的大地构造背景。根据分析样品的元素和Nd同位素特点,推测榴辉岩原岩具有板内玄武岩性质,第Ⅰ段岩芯中的片麻岩原岩为玄武质岩浆上升过程中同化地壳物质形成的中性岩,而第Ⅱ段岩芯中的片麻岩原岩为地壳物质重熔形成的酸性岩。因此,深钻榴辉岩和片麻岩原岩为新元古代华南陆块北缘裂谷构造带双峰式岩浆活动的产物,在岩浆侵位过程中经历了高温大气降水热液蚀变。     

云南省癌死亡率与土壤环境中化学元素的关系

癌病严重危害人类生命。研究表明：土壤环境中微量元素与肿病发生发展以及治疗相关，个别地区的地方病与元素含量关系密切。对土壤中元素含量研究证实：云南癌死亡率低于全国平均水平。文章详细讨论云南9种频发、52种常见癌症与元素的关系。     

Surface analysis of pyrite in the No. 9 coal seam, Wuda Coalfield, Inner Mongolia, China, using high-resolution time-of-flight secondary ion mass-spectrometry

The chemical composition of pyrite in coal can be used to investigate its geological and mineralogical origin. In this paper, high-resolution time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the chemical composition of various pyrite forms in the No. 9 coal seam (S_t,d=3.46%) from the Wuda Coalfield, Inner Mongolia, northern China. These include bacteriogenic, framboidal, massive, cell-filling, fracture-filling, and nodular pyrites. In addition to Fe⁺ (⁵⁴Fe⁺, ⁵⁶Fe⁺, ⁵⁷Fe⁺), other fragment ions were detected in bacteriogenic pyrites, such as ²⁷Al⁺, Si⁺ (²⁸Si⁺, ²⁹Si⁺, ³⁰Si⁺), ⁴⁰Ca⁺, Cu⁺ (⁶³Cu⁺, ⁶⁵Cu⁺), Zn⁺ (⁶⁴Zn⁺, ⁶⁶Zn⁺, ⁶⁷Zn⁺, ⁶⁸Zn⁺), Ni⁺ (⁵⁸Ni⁺, ⁶⁰Ni⁺, ⁶²Ni⁺), and C₃H₇⁺. TOF-SIMS images show bacteriogenic pyrites are relatively rich in Cu, Zn, and Ni, suggesting that bacteria probably play an important role in the enrichment of Cu, Zn, and Ni during their formation. Intense positive secondary ion fragments from framboidal aggregates, such as ²⁷Al⁺, ²⁸Si⁺, ²⁹Si⁺, AlO⁺, CH₂⁺, C₃H₃⁺, C₃H₅⁺, and C₄H₇⁺, indicate that formation of the framboidal aggregates may have occurred together with clay mineral and organic matter, which probably serve as the binding substance. The intense ions of ²⁸Si⁺ and ²⁷Al⁺ from massive pyrites also suggest that their pores incorporated clay minerals during crystallization. Together with the lowest ²⁸Si⁺/²³Na⁺ value, the intense organic positive secondary ion peaks from cell-filling pyrites, such as C₃H₃⁺, C₃H₅⁺, C₃H₇⁺, and C₄H₇⁺, indicate that pyrite formation may have accompanied dissolution or disintegration of the cell. The intense P⁺ peak was observed only in the fracture-filling pyrite and the highest ²⁸Si⁺/²³Na⁺ value of fracture-filling pyrite reflects its epigenetic origin. Together with XRD and REEs data, the stronger ⁴⁰Ca⁺ in nodular pyrite than other pyrite forms shows seawater influence during its formation.     

煤层倾角与覆岩变形破裂分带

地下采煤中三带(冒落带、裂隙带、弯曲带)高度的判断是预测采空引起地表变形破坏程度的依据。在诸多的影响因素中, 煤层倾角是控制三带高度的最主要因素。建立在实测统计基础上的经验范围值用于三带高度的判断带有一定的人为性。急倾斜煤层中冒落带和裂隙带高度随煤层倾角变化的规律已被褐示[7].通过弹塑性岩石材料的非线性有限元模拟, 本文提出了利用应力重分布图判断中、缓倾角煤层采空区覆岩三带高度的方法, 并应用于实际工程。     

国家气象中心气象要素的客观预报——MOS系统

面向全国2000多个台站，应用数值预报产品释用MOS技术制作温度、降水、相对湿度、风、云量及能见度等要素预报，并实现了预报业务运行。通过建立MOS预报系统，表明预报因子和预报对象的处理，建方程前的参数选择以及预报因子的选取都会影响要素预报的质量，需要做大量的细致工作。预报检验结果显示，降水预报尚未达到可用程度，温度和相对湿度的短期预报在大多数情况下是可用的或是可参考的，但还有待进一步改进。降水预报尚需在预报因子和充分运用多种探测信息方面着手加以改进。     

Mechanism of arrested charnockite formation at Nemmara, Palghat region, southern India

The formation of arrested charnockite is an excellent example of structurally controlled channellised fluid flow along specific sites accompanied by selective elemental mobility and mineralogical changes. The present paper recognises and focuses study on three types of arrested charnockite formation from Palghat region, namely, shear-controlled, foliation parallel and boudin-neck types, and address their spatio-temporal relations to regional-scale charnoenderbite. The shear-controlled and foliation parallel types post-date deformation and migmatisation. The boudin-neck type, on the contrary, is coeval with partial melting and followed the path of cooling and decreasing water activity in the gneiss. K-feldspar veining around plagioclase and quartz, symplectitic intergrowth of biotite+quartz after orthopyroxene and K-feldspar, and fluid inclusion data suggests the presence of alkalic supercritical brine and low-density CO₂-rich fluid during charnockite formation. Charnockite domains developed following the breakdown of hornblende, biotite and quartz are characterised by a more or less pronounced depletion of Fe, Ca, Mg and Ti and trace elements Y and Zr, compared to their counterpart gneiss. REE spectra indicate a subtle depletion in the HREE near the centre of the charnockite domain. Although close-pair samples of gneiss–charnockite are isochemical, on a scale of a few millimetres, bi-directional element movement, related to the formation of new mineral was noted. It is postulated that arrested charnockite formation developed in situ on local scale within the granitic domains of the hornblende-biotite gneiss, in the presence of CO₂-rich fluids and alkalic supercritical saline brine. This process post-dated the time of regional granulite (charnoenderbite) and large regional scale retrogression and migmatisation.     

Element mobility during pyrite weathering: implications for acid and heavy metal pollution at mining-impacted sites

Based on back scattered electron images and electron micro-probe analysis results, four alteration layers, including a transition layer, a reticulated ferric oxide layer, a nubby ferric oxide layer and a cellular ferric oxide layer, were identified in the naturally weathering products of pyrite. These layers represent a progressive alteration sequence of pyrite under weathering conditions. The cellular ferric oxide layer correlates with the strongest weathering phase and results from the dissolution of nubby ferric oxide by acidic porewater. Leaching coefficient was introduced to better express the response of element mobility to the degree of pyrite weathering. Its variation shows that the mobility of S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite is oxidized to sulfuric acid and sulfate that are basically released into to porewater, and heavy metals Co and Bi are evidently released by acid dissolution. As, Cu and Zn are enriched in ferric oxide by adsorption and by co-precipitation, but they would re-release to the environment via desorption or dissolution when porewater pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may pose a substantial impact on water quality. Considering that metal mobility and its concentration in mine waste are two important factors influencing heavy metal pollution at mining-impacted sites, Bi and Co are more important pollutants in this case.