海啸和海啸沉积

综述海啸沉积特征,认为岸上细粒海啸沉积物具有以下特点:（1）地层层序上向上变细、减薄;（2）水流方向的重复反向（即重复的双向水流）;（3）含有撕裂的碎屑;（4）较差的分选性;（5）向陆地延伸更远;但将以上任何单一特征看成是海啸沉积的特征性依据都是不恰当的,需要将以上特征结合起来判断,才能作为海啸沉积的依据。而有关岸上巨砾的海啸或是风暴来源,至今仍争论不清,但较一致认为巨砾堤坝复合体是风暴成因。浅水碎屑海啸岩通常为夹在低能稳定状态的背景沉积粉砂—黏土层内的一套独特砂层,可以根据海啸能量的增加到衰减分为Tna—Tnd四个不同单元;而地震海啸岩通常具有震积岩—海啸岩的沉积序列;碳酸盐海啸岩则显示了与海啸入射流和回流相关的冲刷—充填结构。深海的海啸沉积作用机制仍然不清。尽管海啸传播阶段可以产生地中海A型均质岩,但深海海啸岩可能主要与海啸回流有关,如目前讨论最多的K—T撞击海啸岩。尽管目前的研究促进了对海啸的认识,但存在诸如海啸沉积机制仍然不明确,海啸沉积识别依然困难等许多问题,海啸沉积学的进一步发展将为解决这些问题提供坚实基础。     

Reliability-Based Full-Life Cycle Optimum Design of Offshore Jacket Platform

Based on the consideration of operation environment and structural property, an optimnm design model of offshore jacket platform is developed in this paper, namely, the reliability-based full-life cycle optimum design model. In this model, the time-dependent reliability assessment method for structural members is established by combination of the decrease, of sectional size and performance deterioration of material. The initial investment, maintenance cost and failure loss cost are assembled into the model. The total cost of the platform structure system in its full service period is chosen as the objective function, and the initial reliabilities of the layer elements partitioned in advance are taken as the design variables. Different models are obtained, depending on whether the system reliability eonstraint is considered or not. This optimum design model can result in the lowest full-life cost and the optimal initial layer reliability of an offshore jacket platform in the design of marine structures. The feasibility of this model is illustrated with an actual jacket platform in the Liaodong Gulf as an example.     

藏南地区海相白垩系富有机质沉积的影响因素浅析

藏南地区白垩纪时期广泛沉积了一套海相富有机质沉积物,而其中与C-T界线缺氧事件有关的黑色页岩引起了广泛关注。但是,其有机碳含量与西特提斯相比明显偏低。因此,有关该区对海相白垩纪富有机质沉积影响机制的认识显得尤为重要。文中选取前人研究程度较高的岗巴宗山Ⅱ剖面、定日贡扎剖面和江孜加不拉剖面、床得剖面,利用其相关数据,定量计算了这些剖面的沉积速率、堆积速率和古生产力值。结果表明,藏南地区沉积速率以C-T界线时期最高,而岗巴、定日地区与江孜地区的沉积速率表现出较大的差异,这主要与沉积环境有关;并且在沉积速率<4cm/ka时,随着沉积速率的增加,有机碳含量随之增加,而沉积速率较大时,则关系不明显。江孜地区初级生产力较低,其缺氧期黑色页岩的形成并不是高生产力的结果,可能与缺氧条件的保存作用相关;对于岗巴和定日地区而言,尽管计算的古生产力较低,但碳同位素正偏以及推测存在的沿岸上升洋流表明,该区白垩纪富有机质沉积拥有高的初级生产力和缺氧的保存条件,表明该区有良好的古海洋条件,富有机质沉积的形成是高生产力、缺氧的保存条件以及低的沉积速率(<4cm/ka)共同作用的结果。而产生有机碳偏低,从而使得计算的古生产力值偏低的原因,则可能与成岩后期强烈的风化作用,导致有机碳的损失有关;另外定日地区C-T期有机碳含量偏低则还与其沉积物粒度有关。     

基于混凝土细观结构的钢筋混凝土结构耐久性分析

根据观测水平的不同,混凝土的数值分析尺度通常分为宏观、细观和微观三个层次。由于混凝土各相组成材料孔隙结构的差异性,特别是荷载作用下裂缝和微裂缝的出现,进一步增加了混凝土材料的非均匀性,因此采用基于宏观均质假定的分析方法将无法模拟材料的内部结构。在细观层次上,混凝土看作由硬化水泥浆体、骨料及其界面黏结带组成的三相复合材料。基于混凝土的细观结构,本文提出了适用于物质扩散的细观格构网络模型。该模型运用Voronoi技术划分网格的随机性特点,在网络模型中随机产生裂缝的位置及方向,采用不同类型单元来描述混凝土各相组成材料的扩散性能。通过对开裂混凝土内氯离子扩散过程的数值分析表明,基于混凝土细观结构的数值分析方法是开展钢筋混凝土结构耐久性分析的有效手段。     

西藏措勤盆地下白垩统郎山组白云岩储层的发现 及其油气地质意义

措勤盆地面积约14×104km2,是青藏高原面积仅次于羌塘盆地的第二大海相含油气盆地.已有的研究成果[1-2]表明,措勤盆地自古生界至白垩系发育巨厚的海相碳酸盐岩和碎屑岩沉积,沉积厚度大于10557m,盆地生、储、盖层的时空分布规律显示,上古生界和下白垩统为盆地勘探的主要目的层系,其中下白垩统郎山组碳酸盐岩组成的自生自储型组合,以其沉积厚度大、分布广泛、生油条件较好,成为盆地最有利的成藏组合之一,下白垩统潜在的油气远景资源量达9.39×108t[1],具有良好的油气勘探前景.     

沉积盆地卤水来源的非传统同位素示踪研究进展

世界上大多数的沉积盆地内,在结晶基底或者沉积地层内都有矿化度较高的卤水,由于这些卤水通常携带或富含有钾、硼、锂、溴、碘、铷、铯、稀有气体及重金属元素,因此,它们是地学界的研究热点之一。随着测试技术的不断进步,非传统同位素的应用也日益广泛,但在沉积盆地卤水来源和演化方面的研究还十分薄弱,对卤水的来源和演化也还存在争议。文章回顾了硼、锂、碘和惰性气体氦、氩同位素在卤水来源研究方面的进展,并指出由于单一同位素在解释上的片面性,多种同位素相结合的示踪方法研究沉积盆地卤水的来源是国际趋势。     

Analytical Methods for Prediction of Water Absorption in Cement-Based Material?

The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the square root of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the present study, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to explain the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in this paper.