延安市宝塔区崩滑地质灾害发育特征与分布规律初探

宝塔区地质灾害发育特征是数量多、密度高、变形模数大,规模以中小型为主.滑坡平面形态典型、剪出口高,基本力学模式简单;崩塌规模小、危害大、变形模式多样;不稳定斜坡坡度跨度大、坡形以直线型为主,潜在危害严重;诱发因素清楚、宏观前兆相对明显、可预防性较强.地质灾害在空间上集中分布在四区和三带内,在时间上集中在雨季.     

泡沫塑料富集-石墨炉原子吸收光谱法测定地质样品中微量铊

采用HF-HClO4-HNO3-HCl溶解样品，泡沫塑料富集-石墨炉原子吸收光谱法测定岩石、土壤、水系沉积物等地质样品中微量铊。以抗坏血酸为基体改进剂，Fe^3＋加入量选择100mg，灰化温度为600℃，原子化温度为1600℃。方法用于测定国家一级标准物质，结果与标准值基本一致。方法精密度（RSD，n=8）为2．88％～6．27％，回收率为95．24％～101．3％，检出限可达0．058μg/g。     

Settlement behaviour of a concrete faced rock-fill dam

Settlement behaviour of a concrete faced rock-fill dam (CFRD), Kurtun dam, located in the East Black Sea Region, Turkey, is investigated. This is the first instrumented CRDF in the Country. Two dimensional plane strain finite element analyses were carried out to assess the total stresses and displacements in the dam both for construction and reservoir filling stages by using computer program PLAXIS. Predicted stresses and settlements are compared with those observed and overall the results are found to be in good agreement for the construction stage. Due to the relatively steep abutment slopes, cross-valley arching has a significant effect on stresses and displacements in the dam body. For the reservoir filling condition, it is seen that, predicted settlements are larger than the observed values, which indicates that during reservoir filling the rock-fill embankment responds more stiffly than it does during the construction stage. The hardening soil model is used to represent the non-linear, inelastic and stress dependent behaviour of rock-fill material. The model parameters are selected from the appropriate values in the literature investigating comparable cases.     

恢复力模型研究现状及存在问题

恢复力模型是根据大量从试验中获得的恢复力与变形的关系曲线经适当抽象和简化而得到的实用数学模型，是结构构件的抗震性能在结构弹塑性地震反应分析中的具体体现。对迄今为止国内外关于钢筋、混凝土和钢筋混凝土结构构件的恢复力模型的研究成果进行了汇总和简要评述，分析了现有恢复力模型存在的主要问题，在此基础上提出恢复力模型今后的研究建议。     

Evolution of the Variscan foreland-basin: modelling the interactions between tectonics and surface processes

The geology of Western and Central Europe is significantly influenced by the Variscan orogen that developed during Devonian and Carboniferous time. Numerical models are essential in understanding and quantifying the involved endogenous and exogenous processes and their interactions. These are mainly based on the large-scale mass redistribution caused by erosion and fluvial sedimentary transport. The sedimentary mass flux leads to changing loads on the lithosphere and affects therefore the evolution of the orogen and the foreland-basin. The complex feedback-mechanism of the surface and tectonic processes is studied by three-dimensional elastic–plastic numerical models. The calculated uplift rates are used to model the interaction between tectonic and surface processes such as erosion and sedimentation. An iterative application of the numerical models for the tectonic and surface processes yields a detailed view of the evolution of the foreland-basin. The tectonic model itself (excluding surface processes) already shows some of the palinspastically reconstructed important features of the lower Carboniferous like the London-Brabant Massif, and the northward propagation of the Variscan deformation front. The results obtained from the coupled analysis can be compared to studies of the sedimentary record (i.e. time, thickness, and sedimentation rates) and other geological concepts (i.e. stability of geological provinces). The results demonstrate that both processes are essential in understanding the complex structural evolution of the Variscides and their foreland. The numerical approach on the tectonic–surface process interaction can also be applied easily to other geological settings.     

Origin of honeycombs and related weathering forms in Oligocene Macigno Sandstone,Tuscan coast near Livorno,Italy

Two types of cavernous‐weathering features are exposed in the Oligocene Macigno Sandstone along 5 km of the Tuscan coast south of Livorno, Italy. Honeycomb cells (type 1 features) are typical closely spaced, more or less circular pits of centimetre scale that have been eroded 2 to 6 cm below the general surface of bedding planes or joints. ‘Aberrant honeycomb’ cells (type 2 features) are highly elongate, polygonal, or irregular ?at depressions of decimetre scale surrounded by walls rarely higher than 2 cm, some of which pass into long, free‐standing walls or tendrils. Thus, not all type 2 ‘honeycomb’ cells are fully enclosed. We measured the geometry of 551 honeycomb cells and examined various rock properties (microscopic texture and fabric, mineralogy, porosity, permeability, and chemical composition) to isolate factors that control the size, shape, distribution, and pattern of the honeycombs. Our goal was to narrow potential origins of the features and to understand their formation. The ubiquitous occurrence of sea salt in the honeycombs and scanning electron microscope evidence of physical weathering of silicates, especially micas, favours an origin for the honeycombs chie?y by salt weathering. Honeycombs do not form in siltstone, iron‐oxide‐impregnated sandstone, calcite‐cemented concretions, or in case‐hardened joints. Thus, salt weathering of type 1 and 2 honeycombs is not effective in very low permeability rocks. We propose for type 1 honeycombs that seawater is drawn into micropores of the sandstone and evolves into self‐organized diffusion cells (Turing patterns). Selective evaporation at the stationary nodes of diffusion cells, which form at the same site over time, leads to the precipitation of salt, then grains spall off, and pits are formed. The deepest pits (>40 mm) formed where Turing patterns consistently formed at the same sites. Although the walls are more porous and weathered than the host sandstone, they become selectively case hardened by an unidenti?ed component of low abundance. Initial honeycomb cell shape and gravity locally in?uenced type 1 honeycomb shapes. We suggest that type 2 honeycombs develop where diffusion‐controlled Turing patterns lead to case‐hardening along linear trends; gravity and rock fabric are important locally in in?uencing the orientation of the walls. Only type 2 cells are forming today, suggesting recent environmental changes. Gravity is not a fundamental control on honeycomb shape; in places it is a contributing factor. Pre‐existing depressions (quarry tool marks) have strongly in?uenced honeycomb shape locally. Copyright © 2004 John Wiley & Sons, Ltd.     

单体经济模型下市场均衡状态利润成本变动规律浅析

微观经济学研究单体经济模型中经济活动个体的经济行为 ,核心是价格决定理论。商品的价格是由市场中对这种商品的供给和需求决定的。供给和需求相反的作用力 ,使商品达到市场均衡状态。当商品的生产成本发生变化时 ,供给函数发生变化 ,达到新的市场均衡。但均衡利润呈现出与生产成本变动相反的变化趋势。本文试图对其变化规律做出探讨。     

东天山康古尔塔格金矿带地质特征及成矿规律

康古尔塔格金矿带位于塔里木和准噶尔两大板块的碰撞活动地带，EW长200km，有金矿床(点)二十多处。矿床主要产于下石炭统阿奇山组中酸性火山岩中，具层控性，各类岩石Au平均含量高出地壳克拉克值的3—11倍。华力西中晚期—印支早期中酸性浅成相侵入岩类与金成矿关系密切。沿康古尔塔格和苦水断裂发育一系列平行韧性剪切带，是金矿床产出的主要部位。金矿带具水平分带和垂直分带性，金矿脉呈带呈群分布，成矿具有阶段性，矿床类型主要为蚀变岩型和石英脉型，成因属中浅成中低温热液型矿床。     

Pore pressure tension cut off in two-phase finite element analyses

In the coupled finite element analysis of the two-phase, saturated soils the pore pressure could decrease below the atmospheric pressure in particular when the plastic dilation of the skeleton is accounted for. The consequent reduction of the bulk modulus of the liquid phase is here modelled in a simplified manner through a tension cut off on the pore pressure. Two alternative approaches are outlined in the framework of the finite element method. The first one introduces a unilateral constraint on the nodal pore pressures and involves manipulations on matrices of the assembled mesh, whilst the second approach requires calculations solely at the element level. The effects of the pore pressure tension cut off are illustrated through some undrained test examples in elastic–plastic regime.     

A Developed Algorithm of Apriori Based on Association Analysis

A method for mining frequent itemsets by evaluating their probability of supports based on association analysis is presented. This paper obtains the probability of every 1-itemset by scanning the database,then evaluates the probability of every 2-itemset, every 3-itemset, every k-itemset from the frequent 1-itemsets and gains all the candidate frequent itemsets. This paper also scans the database for verifying the support of the candidate frequent itemsets. Last, the frequent itemsets are mined. The method reduces a lot of time of scanning database and shortens the computation time of the algorithm.