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471.
Shen Yang Xue Shen Hanlong Liu Huayang Ge Xiaoxi Rui 《Marine Georesources & Geotechnology》2020,38(6):706-715
AbstractConstruction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content. 相似文献
472.
Young-Ok Kim Eun Jin Yang Jung-Hoon Kang Kyoungsoon Shin Man Chang Cheol Soo Myung 《Ocean Science Journal》2007,42(1):9-17
The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and
heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake
Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semienclosed, inner
area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. 0.4 mg L1) and high concentrations of inorganic nutrients (nitrogenous nutrients >36 μM, phosphate <4 μM) in the bottom layer. Higher
densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while
microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed
into more than 106 cells L1 at the surface layer of the inner area, while its abundance was much lower (103-104 cells L1) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p <
0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to theT. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing
of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates. 相似文献
473.
The responses of a spar constrained by slack mooring lines to steep ocean waves and tensions in the mooring lines are simulated using two different numerical schemes: a quasi-static approach (SMACOS) and a coupled dynamic approach (COUPLE). The two approaches are the same in computing wave loads on the structure. Their difference is in modeling dynamic forces of mooring lines; that is the dynamic forces are included in the computation of COUPLE but neglected in SMACOS. The numerical simulation is examined against the laboratory measurements of the JIP Spar in a water depth of 318 m. The dynamic coupling effects between the JIP Spar and its mooring lines in different water depths (318, 618 and 1018 m) are investigated by the comparison of numerical simulations obtained using the quasi-static and coupled dynamic approaches. It is found that the damping of mooring lines reduces the slow-drift surge and pitch of the Spar, especially in deep water. The reduction in the amplitude of slow-drift surge can reach about 10% in a water depth of 1018 m. The tension in mooring lines may greatly increase in the wave frequency range when dynamic forces in mooring lines are considered. The mooring-line tension in the wave frequency range predicted by the coupled dynamic approach can be eight times as great as the corresponding prediction by the quasi-static approach in a water depth of 1018 m. This finding may have important implications for the estimation of the fatigue strength and life span of the mooring lines deployed in deep water oceans. 相似文献
474.
475.
根据我们实测的水深、重力连续剖面资料,计算了自东海至北斐济盆地的地壳厚度。本文旨在对冲绳海槽至马里亚纳海沟的重力异常和地壳结构进行初步的研究。该地段位于太平洋板块俯冲带以西,构造活动十分复杂、剧烈,并含有多种类型的地壳结构。 相似文献
476.
477.
N,N-二烷基酰胺类物质的膜状态及其在水面溢油集油剂中的应用研究 总被引:1,自引:0,他引:1
合成了 5种 N,N-二烷基酰胺型表面活性剂 ,并对其所成膜的状态进行了测定。表明当N,N-二烷基酰胺类物质单独成膜时获得的集油膜为多层膜 ,而当选用合适的溶剂与其配制成溶液以后 ,所成的集油膜则为转变膜或液态凝聚膜。在 5种 N,N-二烷基酰胺类物质中 ,酰基碳链越长、氮烷基碳链越短则其集油能力越强。应用 N,N-二烷基酰胺类物质配制了 4个配方 ,均具备良好的集油能力 ,并且对原油的集油能力大于对柴油的集油能力 相似文献
478.
采用长期概率预报提供波浪要素设计值是海洋工程中不可缺少的内容之一,文中介绍了一种基於贝叶斯原理的新计算方法,它较传统统计方法有明显的优越性,不仅可以通过补充新信息不断修正原有的估算结果,而且可以避免传统方法带来诸多不确定性,文中以北海中部百年一遇设计波高为例进行了计算。 相似文献
479.
480.
晚中生代─新生代南海周缘地块运动与南海演化 总被引:1,自引:0,他引:1
报道了由华南几个盆地的古地磁数据综合而得的反映该区白垩纪以来古纬度变化曲线,结合Schmidtke等(1990)发表的加里曼丹150Ma以来的古地磁数据,表明华南与加里曼丹在40Ma前具有大致相同的古纬度变化史,差异仅出现在距今30Ma前后和10Ma以来。若此趋势可靠,则可作出下列推断:(1)南海的扩张只能发生在距今30Ma附近或10Ma以后华南与加里曼丹反向运动时期;距今30Ma的扩张已被广为接受;(2)华南与加里曼丹之向可能存在的古南海只能在91Ma之前存在;(3)南海演化可能存在两期扩张。南海的拟合可通过沿3500m等深线的先道时针旋转、后北向平移两个步骤完成。这与Hayashida等(1991)提出的日本海张开与扩张模式很相似,提示东亚边缘海的形成和演化可能具有同样的机制。华南距今50Ma以来的古纬度变化与Tapponnier(1982)的传播挤出构造模式所预期的基本吻合,表明距今50Ma以来华南古纬度变化的运动学机制可用Tapponnier模式作解释。 相似文献