福建滨海沙滩保护和利用的建议

据调查,福建沿海分布有143处主要滨海沙滩,其中已开发利用28处,可合理利用81处,需加强生态保护修复的有21处,被严重破坏已不适宜做海滩资源的有13处。本文在介绍福建滨海沙滩分布及其资源特点基础上,阐述了沿海各地海滩资源的保护与利用现状,分析了主要的资源环境问题及成因,提出了制度建设、资源管控、优化岸滩工程、污染治理、公众宣传、资金保障等有针对性的对策措施。     

含水合物粉细砂的三轴试验及模拟

利用水饱和法制备含天然气水合物试样,进行等向压缩试验和不排水三轴试验.采用天然气水合物临界状态(M HCS)模型同时预测排水条件和不排水条件下的三轴试验,并进行变动参数分析.不排水条件下,密实纯砂发生应变硬化,而相近密实度的含水合物试样出现应变软化,峰值偏应力随水合物饱和度和围压增大.通过与排水和不排水三轴试验结果的对...     

Modelling the effect of wave overtopping on nearshore hydrodynamics and morphodynamics around shore-parallel breakwaters

Wave overtopping nearshore coastal structures, such as shore-parallel breakwaters, can significantly alter the current circulation and sediment transport patterns around the structures, which in turn affects the formation of tombolos and salients in the nearshore area. This paper describes the implementation of a wave overtopping module into an existing depth-averaged coastal morphological mode: COAST2D and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore-parallel breakwaters. The hydrodynamic aspects of the model were validated against a series of laboratory conditions. The model was then applied to a study site at Sea Palling, Norfolk, UK, where 9 shore-parallel segmented breakwaters including 4 surface-piercing and 5 low-crested breakwaters are present, for the storm conditions in Nov 2006. The model results were compared with laboratory data and field measurements, showing a good agreement on both hydrodynamics and morphological changes. Further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation, sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro-tide conditions. The results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures.     

西湖凹陷Y构造花港组气藏特征及成藏主控因素

以常规和非常规油气成藏理论为指导,结合储层、流体等测试分析结果,开展西湖凹陷Y构造花港组气藏特征及成藏主控因素研究。结果表明：① 花港组垂向上符合中下部致密砂岩气、上部常规天然气藏的分布序列;② 常规气藏气水关系正常,受断盖配置对沿断裂运移油气的封闭作用和断层侧向封堵能力影响,油气主要在区域盖层之下的断背斜顶部富集;③ 致密气藏具叠覆跨越源储组合关系,含气饱和度低,无明显气水界面,属先致密后成藏类型,不同部位含气性受构造幅度和储层物性共同控制。本次研究丰富和完善了西湖凹陷常规-非常规天然气序列成藏规律,并为致密砂岩气的勘探提供理论指导。     

A Lagrangian study of the near-surface intrusion of Pacific water into the South China Sea

Satellite-tracked Lagrangian drifters are used to investigate the transport pathways of near-surface water around the Luzon Strait. Particular attention is paid to the intrusion of Pacific water into the South China Sea(SCS).Results from drifter observations suggest that except for the Kuroshio water, other Pacific water that carried by zonal jets, Ekman currents or eddies, can also intrude into the SCS. Motivated by this origin problem of the intrusion water, numerous simulated trajectories are constructed by altimeter-based velocities. Quantitative estimates from simulated trajectories suggest that the contribution of other Pacific water to the total intrusion flux in the Luzon Strait is approximately 13% on average, much smaller than that of Kuroshio water. Even so, over multiple years and many individual intrusion events, the contribution from other Pacific water is quite considerable. The interannual signal in the intrusion flux of these Pacific water might be closely related to variations in a wintertime westward current and eddy activities east of the Luzon Strait. We also found that Ekman drift could significantly contribute to the intrusion of Pacific water and could affect the spreading of intrusion water in the SCS. A case study of an eddy-related intrusion is presented to show the detailed processes of the intrusion of Pacific water and the eddy-Kuroshio interaction.     

Hydrodynamic characteristics and sediment transport of a tidal river under influence of wading engineering groups

By taking the Yong River for example in this paper, based on the multiple measured data during 1957 to 2009, the change process of runoff, tide feature, tidal wave, tidal influx and sediment transport are analyzed. Then a mathematical model is used to reveal the influence mechanism on hydrodynamic characteristics and sediment transport of the wading engineering groups such as a tide gate, a breakwater, reservoirs, bridges and wharves, which were built in different periods. The results showed the hydrodynamic characteristics and sediment transport of the Yong River changed obviously due to the wading engineering groups. The tide gate induced deformation of the tidal wave, obvious reduction of the tidal influx and weakness of the tidal dynamic, decrease of the sediment yield of flood and ebb tide and channel deposition. The breakwater blocked estuarine entrances, resulting in the change of the tidal current and the reduction of the tidal influx in the estuarine area. The large-scale reservoirs gradually made the decrease of the Yong River runoff. The bridge and wharf groups took up cross-section areas, the cumulative affection of which caused the increase of tidal level in the tidal river.     

Behavior of soil plugs in open‐ended model piles driven into sands

Calibration chamber tests were conducted on open‐ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on load transfer mechanism in the soil plug. The model pile used in the test series was devised so that the bearing capacity of an open‐ended pile could be measured as three components: outside shaft resistance, plug resistance, and tip resistance. Under the assumption that the unit shaft resistance due to pile‐soil plug interaction varies linearly near the pile tip, the plug resistance was estimated. The plug capacity, which was defined as the plug resistance at ultimate condition, is mainly dependent on the ambient lateral pressure and relative density. The length of wedged plug that transfers the load decreases with the decrease of relative density, but it is independent of the ambient pressure and penetration depth. Under several assumptions, the value of earth pressure coefficient in the soil plug can be calculated. It gradually reduces with increase in the longitudinal distance from the pile tip. At the bottom of the soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. This may be attributed to (1) the decrease of friction angle as a result of increase in the effective vertical stress, (2) the difference in the dilation degree of the soil plug during driving with ambient pressures, and (3) the difference in compaction degree of soil plug during driving with relative densities. Based on the test results, an empirical equation was suggested to compute the earth pressure coefficient to be used in the calculation of plug capacity using one‐dimensional analysis, and it produces proper plug capacities for all soil conditions.     

Laboratory Investigation on the Effects of Overconsolidation and Saturation on Undrained Monotonic Shear Behavior of Granular Material

In order to study pore water response and static liquefaction characteristics of silty sand, which has previously experienced liquefaction, two series of monotonic triaxial tests were run on medium dense sand specimens (RD = 50%) at confining pressure of 100 kPa. In the first test series, the influence of the soil saturation under undrained static loading has been studied. It summarizes results of monotonic tests performed on Chlef sand at various values of the Skempton's pore pressure coefficient. Analysis of experimental results gives valuable insights on the effect of soil saturation on sand response to undrained monotonic paths. In the second series of tests, the overconsolidation influence on the resistance to the sands liquefaction has been realized on samples at various values of overconsolidation ratios (OCR). It was found that the increase of overconsolidation ratio (OCR) increases the resistance of sands to liquefaction.     

Evaluation of Liquefaction Potential Index Along Western Coast of South Korea Using SPT and CPT

For South Korea, liquefaction potential along the western coast has not been widely assessed because South Korea is considered to be a low seismic hazard. However, recent earthquake events and historical records indicate that the seismic hazard of South Korea should not be ignored. Moreover, as artificial fills are extensively used along the western coast for development, liquefaction evaluation of the soils in this area is necessary. In this paper, we present: (1) the seismic characteristics of the study area; (2) procedures for evaluating liquefaction potential, focusing on the liquefaction potential index (LPI) approach; and (3) LPI distributions at several representative locations along the western coast of South Korea under various seismic scenarios. The liquefaction potential index represents the liquefaction potential over the upper 20 m of a boring or sounding. Using cone penetration test (CPT) and standard penetration test (SPT) data from two coastal sites, we compare and discuss CPT-based and SPT-based LPI values, particularly values computed in nonplastic, silt-rich soils. In these soils, it appears that the CPT yields lower liquefaction resistance, resulting in large LPI values. Finally, discussion and suggestions are provided for CPT- and SPT-based liquefaction assessment of low plasticity and high fines content soils.     

大河影响下的边缘海沉积有机碳输运与埋藏及再矿化研究进展

大河影响下的边缘海是陆源输入物质的主要储库,也是有机碳埋藏和再矿化的主要场所,在全球碳的生物地球化学循环中有着重要作用。从有机碳的输运、埋藏和再矿化等方面综述了大河影响下的边缘海沉积有机碳生物地球化学研究的最新进展。研究表明,有机碳的来源、组成、粒径和密度分布等显著影响着有机碳的分布特征和归宿,大河影响下的边缘海中移动泥等特殊沉积环境在有机碳的输运、埋藏和再矿化分解等方面发挥了独特的作用;微生物分解作用则是边缘海沉积有机碳,特别是难降解陆源有机碳发生分解的重要因素。综合运用分子生物学、有机地球化学、生物地球化学等多学科研究手段,深入研究特定微生物、浮游生物功能类群等在大河影响下的边缘海沉积有机碳生物地球化学过程中的作用,将极大地丰富对河口和陆架边缘海生源要素生物地球化学循环的认识。