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Offshore pipelines are critical infrastructures and any possible damage may have devastating financial and environmental consequences. Earthquake-related geohazards (such as strong ground motion, active seismic faults, submarine landslides and debris flows) consist crucial threats that an offshore pipeline has to overcome. The main aim of the current study is to examine analytically a seabed-laid offshore pipeline subjected to a lateral kinematic distress due to a submarine landslide or a debris flow. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response, by the realistic representation of the soil resistance via a tri-linear model. Firstly, the proposed analytical model is validated with a numerical model utilizing the finite-element method. Subsequently, various combinations of soil parameters and loading conditions that affect the examined problem are investigated with realistic input data taken from the offshore section of the high-pressure natural-gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and the efficiency of the proposed approach. 相似文献
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The majority of coalbed methane(CBM) in coal reservoirs is in adsorption states in coal matrix pores. To reveal the adsorption behavior of bituminous coal under high-temperature and high-pressure conditions and to discuss the microscopic control mechanism affecting the adsorption characteristics, isothermal adsorption experiments under hightemperature and high-pressure conditions, low-temperature liquid nitrogen adsorption-desorption experiments and CO2 adsorption experiments were performed on coal samples. Results show that the adsorption capacity of coal is comprehensively controlled by the maximum vitrinite reflectance(Ro, max), as well as temperature and pressure conditions. As the vitrinite reflectance increases, the adsorption capacity of coal increases. At low pressures, the pressure has a significant effect on the positive effect of adsorption, but the effect of temperature is relatively weak. As the pressure increases, the effect of temperature on the negative effect of adsorption gradually becomes apparent, and the influence of pressure gradually decreases. Considering pore volumes of pores with diameters of 1.7-100 nm, the peak volume of pores with diameters 10-100 nm is higher than that from pores with diameters 1.7-10 nm, especially for pores with diameters of 40-60 nm, indicating that pores with diameters of 10-100 nm are the main contributors to the pore volume. The pore specific surface area shows multiple peaks, and the peak value appears for pore diameters of 2-3 nm, indicating that this pore diameter is the main contributor to the specific surface area. For pore diameters of 0.489-1.083 nm, the pore size distribution is bimodal, with peak values at 0.56-0.62 nm and 0.82-0.88 nm. The adsorption capability of the coal reservoir depends on the development degree of the supermicroporous specific surface area, because the supermicroporous pores are the main contributors to the specific pore area. Additionally, the adsorption space increases as the adsorption equilibrium pressure increases. Under the same pressure, as the maximum vitrinite reflectance increases, the adsorption space increases. In addition, the cumulative reduction in the surface free energy increases as the maximum vitrinite reflectance increases. Furthermore, as the pressure increases, the surface free energy of each pressure point gradually decreases, indicating that as the pressure increases, it is increasingly difficult to adsorb methane molecules. 相似文献
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A unique type of Nb–Zr–REE–Ga-enriched alkali tonstein of pyroclastic origin occurs exclusively within the late Permian coal measures of southwest China. The alkali tonsteins are located within the lowest Xuanwei or Longtan formations of Wuchiapingian age, indicating that their age is later than the main episode of Emeishan Large Igneous Province (ELIP) magmatism. The alkali tonsteins have intermediate–felsic Al2O3/TiO2 values (12.6–34.2, mean 22.0), light rare earth element-enriched chondrite-normalised patterns, negative δEu and incompatible element ratios similar to those of ELIP alkaline Nb–Ta-enriched syenites. All available evidence shows that the alkali tonsteins from southwest China originated from coeval ELIP alkaline magmatism. The enrichment of Nb–Zr–REE–Ga in alkali tonsteins is derived from the ELIP alkaline Nb–Ta-enriched volcanic ashes and may represent the last stage of mineralisation associated with the Emeishan mantle plume activity. 相似文献
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The sediments of the Port Camargue marina (South of France) are highly polluted by Cu and As (Briant et al., 2013). The dynamics of these pollutants in pore waters was investigated using redox tracers (sulfides, Fe, Mn, U, Mo) to better constrain the redox conditions.In summer, pore water profiles showed a steep redox gradient in the top 24 cm with the reduction of Fe and Mn oxy-hydroxides at the sediment water interface (SWI) and of sulfate immediately below. Below a depth of 24 cm, the Fe, Mn, Mo and U profiles in pore waters reflected Fe and Mn reducing conditions and, unlike in the overlying levels, sulfidic conditions were not observed. This unusual redox zonation was attributed to the occurrence of two distinct sediment layers: an upper layer comprising muddy organic-rich sediments underlain by a layer of relatively sandy and organic-poor sediments. The sandy sediments were in place before the building of the marina, whereas the muddy layer was deposited later. In the muddy layer, large quantities of Fe and Mo were removed in summer linked to the formation of insoluble sulfide phases. Mn, which can adsorb on Fe-sulfides or precipitate with carbonates, was also removed from pore waters. Uranium was removed probably through reduction and adsorption onto particles. In winter, in the absence of detectable pore water sulfides, removal of Mo was moderate compared to summer.Cu was released into solution at the sediment water interface but was efficiently trapped by the muddy layer, probably by precipitation with sulfides. Due to efficient trapping, today the Cu sediment profile reflects the increase in its use as a biocide in antifouling paints over the last 40 years.In the sandy layer, Fe, Mn, Mo and As were released into solution and diffused toward the top of the profile. They precipitated at the boundary between the muddy and sandy layers. This precipitation accounts for the high (75 μg g−1) As concentrations measured in the sediments at a depth of 24 cm. 相似文献
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早白垩世泥炭地净初级生产力及其控制因素--来自二连盆地吉尔嘎郎图凹陷6号煤的证据 总被引：2，自引：0，他引：2
现代泥炭地中蕴藏着巨量的碳,泥炭地生产力的高低会影响全球碳循环及全球气候变化。前人对全新世以来泥炭地生产力做了大量研究,但对前第四纪的“深时”阶段的泥炭地生产力则极少涉及,其主要原因是缺少精确的定年方法。以二连盆地吉尔嘎郎图凹陷早白垩世6号煤为例,利用地球物理测井信号进行频谱分析并获得煤层中米兰科维奇旋回周期参数（123 ka（偏心率）:38.1 ka（斜率）:22.1 ka（岁差））,将米兰科维奇旋回作为“深时”地层时间的“度量”工具,计算出6号煤层碳的聚集速率为35.1~38.9 g C/（m2·a）,进一步推算出其所代表的泥炭地的碳聚集速率为46.2~51.2 g C/（m2·a）,净初级生产力（NPP）为231~256 g C/（m2·a）。将该计算结果与全新世同一纬度带泥炭地生产力水平比较,并结合前人研究成果综合分析影响因素,得出早白垩世泥炭地生产力水平主要受温度和大气中二氧化碳含量控制,而这两种因素又与气候相关联,则泥炭地生产力的研究可能对进一步了解古气候提供帮助。 相似文献
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通过有机碳测定、岩石热解分析、显微组分定量分析、饱和烃色谱、色谱-质谱等实验分析,对莺琼盆地中新统海相烃源岩的地球化学特征进行了研究,探讨了不同层位烃源岩的生烃潜力。结果表明：莺琼盆地中新统海相烃源岩有机质丰度总体较低,大部分烃源岩为中等烃源岩,有机质类型以Ⅱ2型和Ⅲ型为主,有机质热演化主要处于成熟阶段。烃源岩显微组分组成具有富含镜质组、壳质组+腐泥组次之、贫含惰性组的特征。烃源岩沉积环境主要为弱氧化-弱还原环境,具有陆生高等植物和低等水生生物生源混合输入的特征。莺歌海盆地梅山组烃源岩综合评价为中等烃源岩,生烃潜力相对较好,三亚组烃源岩综合评价为较差—中等烃源岩,具有一定的生烃潜力。琼东南盆地梅山组和三亚组烃源岩综合评价为中等烃源岩,具有相当的生烃潜力。 相似文献
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空间推理是地球空间信息、人工智能、自然语言处理等相关领域的热点研究内容。主方向关系的表达与推理是空间推理的重要组成部分。针对空间方向关系矩阵对凹边形对象方向关系表达、推理的不足,研究依据目标对象与凹边形地标方向关系表达的不确定性,提出了凹边形地标参照的外部性主方向关系与内部性主方向关系推理方法。利用凹边形三等分仿射变换矩阵、自适应分割算法实现凹边形地标外部性、内部性参照对象表达;基于向量三角形法则与方向关系谓词,以方向关系的逻辑和、逻辑差合成代数运算推理2个地标、1个地标参照下目标对象与参照对象之间的主方向关系。通过实验与算例验证,证明凹边形地标参照下目标对象与参照对象的主方向关系推理可行性。 相似文献
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结合机载LiDAR数据,提出了一种改进的GLAS光斑点冠层高度地形校正模型,以校正后的GLAS光斑点作为输入样本,结合MODIS遥感影像,利用支持向量回归（SVR）的方法对研究区森林冠层高度进行分生态区估测,并利用野外调查数据和机载LiDAR冠层高度结果对估测结果进行验证。结果显示:研究区的坡度等级直接影响GLAS光斑点森林冠层高度估测精度,改进的地形校正模型可以较好的减小坡度对GLAS光斑点森林冠层高度估测的影响,模型精度RMSE稳定在3.25~3.48 m;不同生态分区的SVR模型估测精度较为稳定,其RMSE=6.41~7.56 m;与算数平均高相比,样地的Lorey's高与制图结果拟合最好,不同生态分区平均估测精度为80.3%。机载LiDAR冠层高度结果的验证平均精度为79.5%,和Lorey's高验证结果呈现较好的一致性。 相似文献
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《Journal of Applied Geophysics》2007,61(1):56-81
Due to the character of seismic energy generation and propagation, shallow high-resolution seismic-reflection surveys often fail in the identification of the shallowest horizons and, due to the limited offsets, accuracy of velocity analyses is often not very high.In recent years, Rayleigh wave dispersion analysis have proved to have good potential also for near-surface applications but dispersion curve inversion and related uncertainty evaluation pose serious problems to a completely stand-alone application.In order to overcome these problems a joint inversion scheme is proposed, which is based on the identification of the Pareto front, performed in the framework of a Multi-Objective Evolutionary Algorithm (MOEA). Seismic data considered to design the two objectives are the Rayleigh wave dispersion curve and reflection travel times.We initially analyse a set of synthetic cases and evaluate the obtained results. A significant improvement of the retrieved models is observed as long as reflection travel times are added to the dispersion curve alone.Furthermore, the proposed methodology also provides relevant indications about the consistency of the overall inversion process. In fact, the distribution of the models in the objective space, the trend of the objectives over the passing generations and the evolution of the Pareto front can provide useful information to evaluate the provisional tentative interpretation (number of strata and reflector identification) inherently adopted for the data inversion.On the basis of the results obtained from the tests on the synthetic datasets, the analyses of a field dataset are interpreted as possible evidence of lateral heterogeneities. 相似文献