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海洋环境下粉煤灰混凝土的抗冻性与抗氯离子渗透性的耦合 总被引：1，自引：0，他引：1
针对海洋环境条件,重点研究了粉煤灰混凝土的抗冻性和氯离子渗透性能的相互关系.试验分别研究了水胶比、粉煤灰等量取代水泥掺量大小、引气剂掺量等因素对抗冻性和抗氯离子渗透性能的影响,并与普通混凝土进行了对比.结果表明,粉煤灰不增加混凝土的抗海水冻融耐久性;粉煤灰增加混凝土的抗氯离子渗透性能,但是掺量超过30%,抗氯离子渗透性能下降;粉煤灰对混凝土抗冻性和抗氯离子渗透性的耦合影响在30%左右存在一个最佳掺量.为评估混凝土的抗冻性和氯离子扩散性的耦合性能,提出了新的评价方法--冻渗比(R值方法),并进行了试验验证.SEM和MIP微观分析与R值方法评价的结果是吻合的. 相似文献
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海洋混凝土结构的表面氯离子浓度反映了海洋氯化物环境的腐蚀作用强度,是海洋混凝土结构耐久性分析和定量设计的重要参数。本文依据国内外不同地区的大量自然暴露试验数据,通过数理统计和回归分析,确定了各种海洋环境条件下表面氯离子浓度的统计特征值,分析了海洋潮汐浪溅区混凝土中氯离子的传输机理和积聚规律,揭示了水胶比对混凝土表面氯离子浓度的影响规律,进而综合考虑水胶比、胶凝材料种类和时变特性等因素的影响,建立了海洋潮汐浪溅区混凝土表面氯离子浓度的改进计算模型。结合国内外各种表面氯离子浓度经验模型的预测结果和海洋自然暴露试验的实测数据,对比验证了所建立表面氯离子浓度计算模型的有效性和适用性,为海洋氯化物环境下混凝土结构的耐久性设计和服役寿命分析提供了重要边界条件。 相似文献
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对服役12年的华南某跨海大桥典型构件开展碳化性能、氯离子扩散性能等指标的耐久性检测,评估了海水环境下掺粉煤灰的高性能混凝土长期耐久性。研究表明:随高程的增加混凝土碳化深度逐渐增大,其中大气区浪溅区水位变动区,碳化作用对粉煤灰混凝土结构耐久性的影响较小;粉煤灰可显著提升实体结构混凝土抗氯离子侵蚀性能,粉煤灰高性能混凝土的氯离子扩散系数不大于0.40×10-12m2/s,比普通混凝土氯离子扩散系数降低了约6倍;利用规范计算了引桥承台混凝土中氯离子含量计算值,其计算值与实测值吻合较好,可用于实体工程混凝土结构的耐久性评估,评估结果显示采用粉煤灰高性能的桥梁典型构件满足100年设计使用寿命的要求。 相似文献
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有氯盐侵蚀的钢筋腐蚀,是钢筋混凝土结构性能劣化的主要原因之一,混凝土构件使用寿命的关键是氯离子的传输速率和使钢筋产生锈蚀的时间。本文以人工鱼礁混凝土构件为研究对象,分析海水氯离子在C30、C35和钢渣复合材料人工鱼礁混凝土中的扩散系数,以混凝土中钢筋锈蚀的临界氯离子浓度为寿命预测的边界条件,利用氯离子扩散模型预测C30、C35和钢渣复合材料人工鱼礁在海水中的腐蚀寿命。研究结果表明,氯离子在混凝土人工鱼礁中的扩散规律基本满足Fick第二定律。通过模型计算得出C30、C35和钢渣复合材料混凝土人工鱼礁的腐蚀寿命分别为51.6,54.8和56.8年。 相似文献
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人工鱼礁在自然海水条件下的腐蚀寿命研究 总被引：1，自引：0，他引：1
有氯盐侵蚀的钢筋腐蚀,是钢筋混凝土结构性能劣化的主要原因之一,混凝土构件使用寿命的关键是氯离子的传输速率和使钢筋产生锈蚀的时间。本文以人工鱼礁混凝土构件为研究对象,分析海水氯离子在C30、C35和钢渣复合材料人工鱼礁混凝土中的扩散系数,以混凝土中钢筋锈蚀的临界氯离子浓度为寿命预测的边界条件,利用氯离子扩散模型预测C30、C35和钢渣复合材料人工鱼礁在海水中的腐蚀寿命。研究结果表明,氯离子在混凝土人工鱼礁中的扩散规律基本满足Fick第二定律。通过模型计算得出C30、C35和钢渣复合材料混凝土人工鱼礁的腐蚀寿命分别为51.6,54.8和56.8年。 相似文献
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钢筋混凝土耐久性海洋暴露试验 总被引：4，自引：0，他引：4
对不同技术条件的钢筋混凝土试件进行长期的海洋暴露腐蚀试验,以了解其服役特性,为钢筋混凝土结构的耐久性设计提供依据。近7年的暴露结果表明：在混凝土中掺加高炉矿渣等活性掺合料,能大大降低氯离子渗透速率,提高钢筋混凝土的耐久性。 相似文献
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表面氯离子含量(C_s)是研究海洋环境条件下混凝土结构耐久性和服役寿命的氯离子扩散方程的边界条件,是海洋混凝土结构耐久性分析和定量设计的重要参数。依据国内外大量自然暴露试验与工程实测数据,通过采用Excel、Origin等数据分析软件进行数据统计和回归分析,确定了海洋混凝土结构表面自由氯离子含量(C_(sf))与表面总氯离子含量(C_(st))之间的相互关系,探讨了海洋混凝土结构的C_(sf)时变规律,建立了C_(sf)与暴露时间之间的关系表达式及其取值范围,并运用可靠度理论和修正氯离子扩散理论分析了C_(sf)时变性对海洋混凝土结构寿命的影响。结果表明:C_(sf)与C_(st)线性相关,且C_(sf)随着暴露时间的延长呈指数或者幂函数的增长关系;采用不同的C_(sf)时变性规律,对海洋混凝土结构寿命具有重大的影响。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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《海洋学报(英文版)》2014,(8):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
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Nabil Sultan Pierre Cochonat Jean Fran ois Bourillet Florence Cayocca 《Marine Georesources & Geotechnology》2001,19(2):107-133
This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed. 相似文献