Finite element formulation and algorithms for unsaturated soils. Part II: Verification and application

The finite‐element formulation and integration algorithms developed in Part I are used to analyse a number of practical problems involving unsaturated and saturated soils. The formulation and algorithms perform well for all the cases analysed, with the robustness of the latter being largely insensitive to user‐defined parameters such as the number of coarse time steps and error control tolerances. The efficiency of the algorithms, as measured by the CPU time consumed, does not depend on the number of coarse time steps, but may be influenced by the error control tolerances. Based on the analyses presented here, typical values for the error control tolerances are suggested. It is also shown that the constitutive modelling framework presented in Part I can, by adjusting one constitutive equation and one or two material parameters, be used to simulate soils that expand or collapse upon wetting. Treating the suction as a strain variable instead of a stress variable proves to be an efficient and robust way of solving suction‐dependent plastic yielding. Moreover, the concept of the constitutive stress is a particularly convenient way of handling the transition between saturation and unsaturation. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of spatial variation characteristics on contouring of design storm depth

The ordinary kriging method, a geostatistical interpolation technique, was applied for developing contour maps of design storm depth in northern Taiwan using intensity–duration–frequency (IDF) data. Results of variogram modelling on design storm depths indicate that the design storms can be categorized into two distinct storm types: (i) storms of short duration and high spatial variation and (ii) storms of long duration and less spatial variation. For storms of the first category, the influence range of rainfall depth decreases when the recurrence interval increases, owing to the increasing degree of their spatial independence. However, for storms of the second category, the influence range of rainfall depth does not change significantly and has an average of approximately 72 km. For very extreme events, such as events of short duration and long recurrence interval, we do not recommend usage of the established design storm contours, because most of the interstation distances exceed the influence ranges. Our study concludes that the influence range of the design storm depth is dependent on the design duration and recurrence interval and is a key factor in developing design storm contours. Copyright © 2003 John Wiley & Sons, Ltd.     

Exposure dating and reinterpretation of coarse debris accumulations (‘rock glaciers’) in the Cairngorm Mountains,Scotland

Relict rock glaciers have considerable potential for contributing to palaeoclimatic reconstruction, but this potential is often undermined by lack of dating control and problems of interpretation. Here we reinvestigate and date four proposed ‘rock glaciers’ in the Cairngorm Mountains and show that the morphology of only one of these appears consistent with that of a true rock glacier produced by creep of underlying ice or ice‐rich sediment. All four features comprise rockslide or rock avalanche runout debris, and the possibility that all four represent unmodified runout accumulations cannot be discounted. Surface exposure dating of the four debris accumulations using cosmogenic ¹⁰Be produced uncertainty‐weighted mean ages of 15.4 ± 0.8 ka, 16.2 ± 1.0 ka, 12.1 ± 0.6 ka and 12.7 ± 0.8 ka. All four ages imply emplacement under cold stadial conditions, two prior to the Windermere Interstade of ca. 14.5–12.9 cal. ka BP and two during the Loch Lomond Stade of ca. 12.9–11.5 cal. ka BP. The above ages indicate that paraglacial rock‐slope failure on granite rockwalls occurred within a few millennia after deglaciation. The mean exposure ages obtained for runout debris at two sites – Strath Nethy (16.2 ± 1.0 ka) and Lairig Ghru (15.4 ± 0.8 ka) – are consistent with basal radiocarbon ages from Loch Etteridge, 22 km to the southwest (mean = 15.6 ± 0.3 cal. ka BP) and imply widespread deglaciation of the Cairngorms and adjacent valleys before 15 ka and possibly 16 ka. Copyright © 2008 John Wiley & Sons, Ltd.     

Uncoupling of coupled flows in soil—a finite element method

Coupled flow of water, chemicals, heat and electrical potential in soil are of significance in a variety of circumstances. The problem is characterized by the coupling between different flows, i.e. a flow of one type driven by gradients of other types, and by the dual nature of certain flows, i.e. combined convection and conduction. Effective numerical solutions to the problem are challenged due to the coupling and the dual nature. In this paper, we first present a general expression that can be used to represent various types of coupled flows in soil. A finite element method is then proposed to solve the generalized coupled flows of convection-conduction pattern. The unknown vector is first decomposed into two parts, a convective part forming a hyperbolic system and a conductive part forming a parabolic system. At each time step, the hyperbolic system is solved analytically to give an initial solution. To solve the multi-dimensional hyperbolic system, we assume that a common eigenspace exists for the coefficient matrices, so that the system can be uncoupled by transforming the unknown vector to the common eigenspace. The uncoupled system is solved by the method of characteristics. Using the solution of the hyperbolic system as the initial condition, we then solve the parabolic system by a Galerkin finite element method for space discretization and a finite difference scheme for time stepping. The proposed technique can be used for solving multi-dimensional, transient, coupled or simultaneous flows of convection-conduction type. Application to a flow example shows that the technique indeed exhibits optimality in convergence and in stability.     

藏北南羌塘盆地毕洛错地区下侏罗统曲色组石膏岩层

对西藏自治区北部南羌塘盆地毕洛错地区下侏罗统曲色组石膏岩层进行了研究。根据岩石地层和生物地层资料,确认毕洛错地区的石膏岩层和油页岩为曲色组的一部分,地质时代为早侏罗世,并确认下侏罗统曲色组在区域上可能是寻找油气、油页岩资源的重要层位之一。     

等温微量热法在土壤微生物研究方面的进展

土壤微生物是陆地生态系统中分解者亚系统的主要组成部分, 参与了包括有机质降解、营养转化、 植物生长的促进或抑制以及各种土壤物理过程在内的一系列反应活动. 土壤微生物则是土壤质量重要的生物指标, 可以用来监控土壤质量的变化. 等温微量热法是一种简便、快速地测量微生物活性的方法, 在土壤微生物代谢热效应的研究领域中广泛应用. 就等温微量热法在土壤微生物活性中的研究进展进行综述: 等温微量热法的简介, 微量热方法与传统方法的比较, 等温微量热法在各种外界环境和土壤条件影响下的土壤微生物活性研究中的应用, 并对等温微量热法在土壤微生物和其它方面的研究进行了展望.     

AN ECOLOGICAL STUDY OF FOULING ORGANISMS IN XISHA ISLANDS

Monthly and seasonal panel experiments were carried out in the Yongxing Island from September 1979 to August 1981. Altogether 119 species of fouling organisms are collected, of which, Hydroides elegans, Serpula vermicular is, Scrupocellaria longispinosa, Amathia distant, Enteromorpha spp. and Ostrea spp. are dominant species. Fouling of organisms may occur all the year round with evident seasonal variations, Species succession in the process of community formation is very evident and the climax has arrived after two years. Great variation exists between fouling organisms in different years and at different stations.     

海上矿石运输最优船队的组建

针对海上矿石运输，介绍了一种完成定量任务并能使投资费用最少为目标的最优船队组建方法，同时对易变参数进行了灵敏度分析，使决策更加科学化     

雪宝顶碱性花岗岩岩石地球化学与成矿控制

对雪宝顶碱性花岗岩具有高丰度的W、Sn、Be含量和W、Sn矿化花岗岩的微量元素组合特征进行了分析，结果显示：稀土元素具有∑REE含量与LREE／HREE比值偏低和负Eu异常的特点；元素比值K／Rb，U／Th，Nb／Ta的规律性变化以及矿脉产状特征等表明W-(Sn)-Be脉状矿床形成于岩浆演化晚期，与岩浆期后的热液活动有关。     

培养基对海藻真菌PT2菌株的生长及活性代谢产物合成的影响

本文采用PD、GPY、YES、SYE、GPM5种不同培养基培养海藻真菌菌株PT2，并对其在不同培养基中的生长情况、代谢产物的形成及抗肿瘤活性进行分析，旨在了解不同培养基对菌株生长和活性物质合成的影响．结果显示，PT2菌株在不同培养基上的培养特征及生长速率有所不同，液体培养基发酵液抽提物的抗肿瘤活性也有较大差别，其中SYE发酵液抽提物活性最强，对KB、Raji和Hela 3种肿瘤细胞的IC50分别为7．6μg／cm^3、2．4μg／cm^3和3．3μg／cm^3．采用HPLC法对不同抽提物进行分析，发现它们之间的组成成分有显著差异．本文的实验结果表明，不同培养基对该菌株的生长及活性代谢产物的合成具有显著的影响。