框格式地下连续墙非线性分析及稳定计算

根据地质及结构特点,建立了能反映框格式地下连续墙力学特性的典型子模型,即槽段有限元模型。基于ABAQUS有限元软件,采用经典的摩尔-库仑（Mohr-Coulomb）屈服准则、非关联流动法则,对框格式混凝土地连墙槽段进行了施工全过程模拟,详细分析了结构在最不利工况下混凝土连续墙的应力与变形,还用强度折减有限元方法分析了该最不利工况下结构的整体稳定性,论证了框格式连续墙这种地基处理方式的合理性与可行性,地下连续墙在应力变形及稳定方面能满足工程需要。     

非均质各向异性软基上管桩基础承载力分析

对于非均质各向异性软土地基上管桩基础的承载力,基于塑性极限分析理论考虑软土强度的非均质与各向异性效应,提出了一种改进的三维极限分析上限解法。利用有限元分析软件ABAQUS,采用Hill理想弹塑性模型,对软基上管桩水平承载力进行了数值模拟,由此所得到的破坏模式与极限分析方法中的假设失稳机制基本一致。通过变动参数对比分析,探讨了软黏土不排水抗剪强度的各向异性和非均质性对于管桩基础承载力的影响。     

样品处理与保存方法对表层沉积物中金属形态分析的影响

利用改进的Tessier连续萃取法研究了冷藏、冷冻、冻干、烘干和风干等样品处理与保存方法对表层沉积物中金属形态的影响。结果表明：各样品处理与保存过程对沉积物中Fe、Mn、Cu、Zn及Pb的形态均具有不同程度的影响,其中Fe的形态受其影响最小（<3.3%）,Mn的形态受其影响最大（最高可达10.2%）;冻干对各金属形态的影响最小（<4.6%）;烘干和风干对重金属Cu、Zn和Pb的可交换态（Ⅰ+Ⅱ）和非残渣态（Ⅰ-Ⅴ）分布影响较大,而冷藏、冷冻和冻干的影响相对较小。因此,综合考虑重金属的形态分布及其生物可利用性,冻干是较理想的沉积物样品处理与保存方法。     

贵州锦丰（烂泥沟）金矿床含砷黄铁矿和脉石英及其包裹体的微量元素特征

贵州锦丰（烂泥沟）金矿是滇黔桂“金三角”目前已探明最大的卡林型金矿床。含砷黄铁矿是该矿床最主要的载金矿物,硅化及石英脉是最显著的热液蚀变类型。本文采用高精度电感耦合等离子质谱（ICP-MS）对含砷黄铁矿和脉石英及其包裹体的微量元素进行了测试,结果表明含砷黄铁矿富亲硫元素,并相对于围岩和上部地壳均强烈富集;亏损V,Sr 及高场强元素。同生黄铁矿也具有类似的特征。脉石英除亲石元素含量高以外,还表现为亲硫元素以及Mo,Bi 含量较高。但与上部地壳相比,绝大部分元素贫化。相应包裹体的微量元素含量普遍低于单矿物,但变化特征一致。结合矿物和包裹体的稀土元素分析,发现脉石英和含砷黄铁矿及其包裹体均表现为HFSE明显亏损,Th/La,Nb/La 比值小于1,说明成矿流体为富Cl 的流体。含砷黄铁矿及其包裹体中Co/Ni 比值远小于1,反映成矿温度较低,推测成矿流体主要来源于以沉积建造水为主的盆地流体。     

A simplified model for lateral response of large diameter caisson foundations—Linear elastic formulation

The transient response of large embedded foundation elements of length-to-diameter aspect ratio D/B=2–6 is characterized by a complex stress distribution at the pier–soil interface that cannot be adequately represented by means of existing models for shallow foundations or flexible piles. On the other hand, while three-dimensional (3D) numerical solutions are feasible, they are infrequently employed in practice due to their associated cost and effort. Prompted by the scarcity of simplified models for design in current practice, we here develop an analytical model that accounts for the multitude of soil resistance mechanisms mobilized at their base and circumference, while retaining the advantages of simplified methodologies for the design of non-critical facilities. The characteristics of soil resistance mechanisms and corresponding complex spring functions are developed on the basis of finite element simulations, by equating the stiffness matrix terms and/or overall numerically computed response to the analytical expressions derived by means of the proposed Winkler model. Sensitivity analyses are performed for the optimization of the truncated numerical domain size, the optimal finite element size and the far-field dynamic boundary conditions to avoid spurious wave reflections. Numerical simulations of the transient system response to vertically propagating shear waves are next successfully compared to the analytically predicted response. Finally, the applicability of the method is assessed for soil profiles with depth-varying properties. The formulation of frequency-dependent complex spring functions including material damping is also described, while extension of the methodology to account for nonlinear soil behavior and soil–foundation interface separation is described in the conclusion and is being currently investigated.     

A positive definite continuous FEM model for advection

This work introduces a continuous and sign-preserving finite element model (FEM) for advection problems. The model is formulated by integrating flux corrected transport technique (FCT) with the characteristic based (CB) FEM. Low order solution for the FCT has the form of element contribution and derives from an upwind monotone scheme with the minimum necessary diffusion for positivity. Selected numerical experiments illustrate the efficacy of the method by comparing results with some successful models, by demonstrating an approximate conservation of the accuracy of original CB algorithm once the complete procedure is operating, and by testing the model for severe time dependent advective flows.     

Adaptation strategy of bivalve Modiolus modiolus from upwelling regions of the Kuril Islands shelf (Sea of Okhotsk) to heavy metal effects

Cd, Cu, Fe, Mn, Ni, Pb, Zn concentration in the organs (muscle, gonads, mantle, gills, digestive gland, kidney) of mussel Modiolus modiolus was studied. Mussels were collected from shelf upwelling sites of Kuril Is. Sea of Okhotsk (104 and 85 m) and, for comparison, coastal high contaminated and clean sites (Peter the Great Bay, Sea of Japan). It was found that mussels from shelf upwelling regions accumulated unusually high Cd concentration in studied organs, excepting digestive gland. Shelf mussels have evolved passive adaptation to elevated level of ambient heavy metals (distribution of heavy metal load between all organs, especially, muscle). In contrast, mussels from high contaminated sites have evolved active adaptation (strong regulation of metal concentration in the organs at the maximal permissible concentration due to increased kidney function). We supported that under natural condition, passive adaptation of aquatic organisms to increased ambient metal level have been evolved only under constant low-water temperature.     

Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China

The trace element and rare earth element (REE) variations across the Ordovician-Silurian succession are presented from two outcrop sections on the Yangtze Platform: the Nanbazi section, Guizhou Province, deposited in a shallow platform interior setting, and the Wangjiawan section, Hubei Province, deposited in a deeper basinal environment. Geochemical analysis of closely spaced samples through three intervals, the Wufeng, Guanyinqiao and Longmaxi, revealed vast palaeoceanographic changes. Some geochemical proxies, including Th/U, Ni/Co, V/Cr, and V/(V+Ni) ratios, together with sedimentary facies and biotic data, indicate that an anoxic condition on the most of the Yangtze Platform during the Wufeng and Longmaxi intervals, but an oxic condition during the Guanyinqiao time. The shift of the anoxic to the oxic environment during the Guanyinqiao time coincided with a global sea-level lowstand, in parallel with the global glaciation. The Longmaxian anoxic environment was a result of a global sea-level rise, which may be synchronized with a mainly catastrophic event in the latest Ordovician. Although the two sections generally show similar variation patterns of trace and REE concentrations and some element ratios, a minor difference occurs between the Wangjiawan and Nanbazi sections, likely reflecting a difference in depositional setting during the accumulation. Such an oceanic oxygen-level variation may add a useful constraint to the current arguments on the cause and consequence of the latest Ordovician mass extinction. Supported by National Basic Research Program of China (Grant No. 2005CB422101)     

Biosorption of Cd(II), Ni(II) and Pb(II) from Aqueous Solution by Dried Biomass of Aspergillus niger: Application of Response Surface Methodology to the Optimization of Process Parameters

In this study, the biosorption of Cd(II), Ni(II) and Pb(II) on Aspergillus niger in a batch system was investigated, and optimal condition determined by means of central composite design (CCD) under response surface methodology (RSM). Biomass inactivated by heat and pretreated by alkali solution was used in the determination of optimal conditions. The effect of initial solution pH, biomass dose and initial ion concentration on the removal efficiency of metal ions by A. niger was optimized using a design of experiment (DOE) method. Experimental results indicated that the optimal conditions for biosorption were 5.22 g/L, 89.93 mg/L and 6.01 for biomass dose, initial ion concentration and solution pH, respectively. Enhancement of metal biosorption capacity of the dried biomass by pretreatment with sodium hydroxide was observed. Maximal removal efficiencies for Cd(II), Ni(III) and Pb(II) ions of 98, 80 and 99% were achieved, respectively. The biosorption capacity of A. niger biomass obtained for Cd(II), Ni(II) and Pb(II) ions was 2.2, 1.6 and 4.7 mg/g, respectively. According to these observations the fungal biomass of A. niger is a suitable biosorbent for the removal of heavy metals from aqueous solutions. Multiple response optimization was applied to the experimental data to discover the optimal conditions for a set of responses, simultaneously, by using a desirability function.     

粉砂地基深基坑渗透破坏研究

在地下水丰富的砂土和粉土地区进行深基坑开挖,坑内降水施工或渗漏引起的渗透破坏问题是威胁基坑稳定性和周围环境的主要因素。通过模型试验结合数值模拟,研究了土体密实度、黏聚力、内摩擦角、桩土界面摩擦特性以及围护结构插入深度等因素对临界水力梯度以及渗透破坏模式的影响。研究表明,发生渗透破坏时的水力坡降不仅与土的密实度有关,还与土性、强度指标、桩表面粗糙度以及围护结构的插入深度等因素有关,这些结论为实际基坑工程分析提供了指导。