上海崇明岛表层土壤重金属元素分布特征与环境地球化学基线值研究   总被引：6，自引：0，他引：6  

刘久臣  刘晓端  徐清  汤奇峰 《岩矿测试》2010,29(3):245-249

对上海崇明岛地区表层土壤中重金属元素的分布特征进行了研究,结果表明崇明岛表层土壤未受人为污染。运用标准化方法计算了崇明岛地区表层土壤中重金属元素镉、铬、铜、铅、锌、砷的环境地球化学基线值,建立了元素镉、铬、铜、铅、锌、砷的环境地球化学基线模型,确定其环境地球化学基线值分别为0.19、71.97、31.32、24.79、86.43、8.34μg/g。与上海市土壤背景值进行了对比检验,结果显示,标准化方法能有效计算土壤中元素的环境地球化学基线,获得的基线符合其定义和实际意义,为区域经济发展规划和环境评价提供了实用的基础地球化学信息。  相似文献   

菲律宾迪纳加特岛红土型镍矿床地质特征及找矿勘查方法   总被引：1，自引：0，他引：1  

王志刚 《地质与勘探》2010,46(2)

通过对菲律宾迪纳加特岛风化壳氧化镍-硅酸镍矿床的成矿地质条件、矿床地质特征、成矿机制的分析和研究,认为矿床是由于超镁铁岩-橄榄岩在中生代、第三纪、第四纪的热带、亚热带气候条件下,经过风化作用,镍从含镍的硅酸盐矿物中淋滤出来,随地表水向下渗透到风化壳的下部,形成富含镍的次生矿物,具有典型的风化壳型硅酸镍矿床特点。找矿勘探工作要在找矿区域进行地质填图及工程取样扫面来确定矿化区。  相似文献   

我国火山灾害的主要类型及火山灾害区划图编制现状探讨   总被引：5，自引：0，他引：5  

许建东 《震灾防御技术》2006,1(3):266-272

通过对《核电厂厂址选择中的地震问题》(HAF0101(1))有关条款的详细剖析,发震构造包括两个方面的含义:一是曾经是地震震源的地质构造;二是未来可能发生破坏性地震的地质构造。地震重演原则和构造类比原则是判定发震构造的两条基本依据,但在实际工作中构造类比原则的应用往往存在较大难度,对中强地震发震构造的判定尤其如此。文中提出:对中强地震构造带地貌差异性和第四纪地层分布特征的研究有可能提供识别发生中强地震地质构造的标志。  相似文献   

山东省海岛资源的旅游再开发研究          下载免费PDF全文

周辉  牛亚菲 《海洋开发与管理》2021,38(5):9-13

山东省是我国北方海岛最多的省份,海岛作为体现城市海岸带风貌的重要海洋空间资源,是山东省开发海洋的重要基地。随着新时代人民美好生活需求的增长,海岛资源的旅游开发再一次成为政府和学界关注的热点,但与海岛建设日趋活跃相比,相关理论研究仍处于相对滞后的状态。文章从山东省海岛资源的特点认知入手,通过明晰政策目标与开发现状之间的差距,提出“一个调整”“三个整合”和“两个优化”的旅游再开发策略。“一个调整”即海岛旅游开发思路方向调整;“三个整合”即青岛、烟台、威海海岛旅游线路整合,重点海岛群旅游产品整合,海岛与陆域旅游要素整合;“两个优化”为已开发海岛的旅游品质优化,无人海岛的扶持政策优化。通过调整、整合和优化策略,逐步落实相关政策目标,为海岛的可持续、高质量发展提供支撑。  相似文献   

基于风暴水流能量分布对海南岛小东海珊瑚巨砾成因的分析*     

王媛琪  杨阳  周亮  汪亚平  高抒 《热带海洋学报》2021,40(4):110-121

波致水流的能量差异有助于风暴和海啸巨砾的区分。本文基于这一思路, 进行风暴波浪和波致水流的能量分析, 给出海岸珊瑚巨砾在风暴潮期间以推移质方式输运的动力学过程表达, 推算出风暴巨砾的理论输运距离。结合海南岛极端事件历史记录, 得出海南岛小东海风暴巨砾在礁坪的分布格局, 并与该海区的巨砾实际分布进行对比。结果表明, 小东海风暴巨砾分布与巨砾的质量、形状及风暴潮能量密切相关。研究区现场观测的大部分巨砾沉积分布符合风暴巨砾的理论空间分布格局, 因而判断其为风暴潮成因堆积。未来经过模拟假设条件的完善, 并构建相应海啸水流输运模式, 可形成用以区分风暴、海啸巨砾的完整判据。  相似文献   

Non‐coaxiality and stress–dilatancy rule in granular materials: FE investigation within micro‐polar hypoplasticity     

Jacek Tejchman  Wei Wu 《国际地质力学数值与分析法杂志》2009,33(1):117-142

This paper deals with FE investigations of shear localization in dilatant granular bodies. The calculations were carried out with a hypoplastic constitutive law enhanced by micro‐polar terms to properly model the shear zone evolution. The behaviour of an initially medium dense sand specimen with very smooth and very rough horizontal boundaries was analyzed during a plane strain compression test. A stochastic distribution of the initial void ratio was assumed to be spatially correlated. Attention was focused on the non‐coaxiality of the directions of the principal strain increments and principal stresses in the shear zone and on the stress–dilatancy rule. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Episodes of reef growth at Lord Howe Island, the southernmost reef in the southwest Pacific   总被引：2，自引：0，他引：2  

C.D. Woodroffe  M.E. Dickson  B.P. Brooke  D.M. Kennedy 《Global and Planetary Change》2005,49(3-4):222-237

Lord Howe Island lies at the present latitudinal limit to reef growth in the Pacific and preserves evidence of episodes of reef development over the Late Quaternary. A modern fringing reef flanks the western shore of Lord Howe Island, enclosing a Holocene lagoon, and Late Quaternary eolianites veneer the island. Coral-bearing beach and shallow-water calcarenites record a sea level around 2–3 m above present during the Last Interglacial. No reefs or subaerial carbonate deposits occur on, or around, Balls Pyramid, 25 km to the south. The results of chronostratigraphic studies of the modern Lord Howe Island reef and lagoon indicate prolific coral production during the mid-Holocene, but less extensive coral cover during the late Holocene. Whereas the prolific mid-Holocene reefs might appear to reflect warmer sea-surface temperatures, the pattern of dates and reef growth history are similar to those throughout the Great Barrier Reef and across much of the Indo-Pacific and are more likely correlated with availability of suitable substrate. Little direct evidence of a Last Interglacial reef is now preserved, and the only evidence for older periods of reef establishment comes from clasts of coral in a well-cemented limestone unit below a coral that has been dated to the Last Interglacial age in a core at the jetty. However, a massive reef structure occurs near the centre of the wide shelf around Lord Howe Island, veneered with Holocene coralline algae. Its base is 40–50 m deep and it rises to water depths of less than 30 m. This fossil reef is several times more extensive than either Holocene or Last Interglacial reefs appear to have been. Holocene give-up reef growth is inferred during the postglacial transgression, but an alternative interpretation is that this is a much older landform, indicating reefs that were much more extensive than modern reefs at this marginal site.  相似文献   

Liquefaction and cyclic mobility model for saturated granular media     

S. Lpez‐Querol  R. Blzquez 《国际地质力学数值与分析法杂志》2006,30(5):413-439

A new constitutive law for the behaviour of undrained sand subjected to dynamic loading is presented. The proposed model works for small and large strain ranges and incorporates contractive and dilative properties of the sand into the unified numerical scheme. These features allow to correctly predict liquefaction and cyclic mobility phenomena for different initial relative densities of the soil. The model has been calibrated as an element test, by using cyclic simple shear data reported in the literature. For the contractive sand behaviour a well‐known endochronic densification model has been used, whereas a plastic model with a new non‐associative flow rule is applied when the sand tends to dilate. Both dilatancy and flow rule are based on a new state parameter, associated to the stiffness degradation of the material as the shaking goes on. Also, the function that represents the rearrangement memory of the soil takes a zero value when the material dilates, in order to easily model the change in the internal structure. Proceeding along this kind of approach, liquefaction and cyclic mobility are modelled with the same constitutive law, within the framework of a bi‐dimensional FEM coupled algorithm developed in the paper. For calibration purposes, the behaviour of the soil in a cyclic simple shear test has been simulated, in order to estimate the influence of permeability, frequency of loading, and homogeneity of the shear stress field on the laboratory data. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Collinear Central Configuration in Four-Body Problem     

Tiancheng Ouyang  Zhifu Xie 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):147-166

In the n-body problem a central configuration is formed if the position vector of each particle with respect to the center of mass is a common scalar multiple of its acceleration vector. We consider the problem: given a collinear configuration of four bodies, under what conditions is it possible to choose positive masses which make it central. We know it is always possible to choose three positive masses such that the given three positions with the masses form a central configuration. However for an arbitrary configuration of four bodies, it is not always possible to find positive masses forming a central configuration. In this paper, we establish an expression of four masses depending on the position x and the center of mass u, which gives a central configuration in the collinear four body problem. Specifically we show that there is a compact region in which no central configuration is possible for positive masses. Conversely, for any configuration in the complement of the compact region, it is always possible to choose positive masses to make the configuration central.  相似文献   

Mohr–Coulomb MiniCLoE model Uniqueness and localization studies,links with normality rule     

R. Chambon  V. Roger 《国际地质力学数值与分析法杂志》2003,27(1):49-68

This paper is devoted to a parametric study of a plane Mohr–Coulomb CLoE model. As CLoE models are designed with a consistency condition, it is possible to define a normality condition and to study its consequences. The positiveness of the second order work which implies the uniqueness of the solution of a small strain boundary value problem is studied firstly. Then the localization criterion is also studied. It is proved that normality has consequences similar to those for classical elasto plastic models. However if induced anisotropy is introduced in the hypoplastic CLoE model, some conclusions are no longer true. Finally plane strain experimental data are used to identify the parameters of the model. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献