The influence of roughness geometry and Shields parameter on flow resistance in gravel-bed channels

The spatial variability of bed particles of a gravel-bed channel is analysed and treated experimentally in order to simulate the effects of the arrangement of coarse bed elements on the flow resistance law. For the studied bed patterns, characterized by the concentration Γ of coarser elements arranged on the bed layer, a particle arrangement parameter α is proposed. The α parameter is useful for estimating the intercept b₀ of the semi-logarithmic flow resistance law deduced by flume measurements carried out for the hydraulic condition of large-scale and transition roughness. The differences between the experimental friction factor parameter values and the ones calculated by the proposed semi-logarithmic relationship are explained by the ratio between the Shields parameter and its critical value. The analysis shows that estimates of the friction factor parameter are not improved by introducing the Froude number into the flow resistance law. © 1997 by John Wiley & Sons, Ltd.     

工程软岩表面形态及其摩擦特性研究

在自然状态和接触面掺泥两种情况下,进行了砂岩、泥岩破裂面及其互层接触的摩擦试验。结果表明:在接触面掺泥时,抗剪强度的粘聚力和内摩擦角都有不同程度的降低,其中粘聚力下降明显,并且摩擦位移与剪应力关系曲线有明显不同,而且粘滑现象明显减弱。结合摩擦试验,研究了砂岩、泥岩在摩擦前后破裂面表面形态的变化,分析了它们的粗糙度及其起伏特性在摩擦前后的变化规律,以及表面特性和摩擦强度的关系。      

Laboratory and numerical studies of wave damping by emergent and near-emergent wetland vegetation

Wetlands protect mainland areas from erosion and damage by damping waves. Yet, this critical role of wetland is not fully understood at present, and a means for reliably determining wave damping by vegetation in engineering practice is not yet available. Laboratory experiments were conducted to measure wave attenuation resulting from synthetic emergent and nearly emergent wetland vegetation under a range of wave conditions and plant stem densities. The laboratory data were analyzed using linear wave theory to quantify bulk drag coefficients and with a nonlinear Boussinesq model to determine numerical friction factors to better represent wetland vegetation in engineering analysis.     

Accurate ocean tide modeling in southeast Alaska and large tidal dissipation around Glacier Bay

An accurate prediction of ocean tides in southeast Alaska is developed using a regional, barotropic ocean model with a finite difference scheme. The model skill is verified by the observational tidal harmonics in southeast Alaska including Glacier Bay. The result is particularly improved in Glacier Bay compared to the previous model described by Foreman et al. (2000). The model bathymetry dominates the model skill. We re-estimate tidal energy dissipation in the Alaska Panhandle and suggest a value for tidal energy dissipation of 3.4 GW associated with the M₂ constituent which is 1.5 times the estimation of Foreman et al. (2000). A large portion of the M₂ energy budget entering through Chatham Strait is dissipated in the vicinity of Glacier Bay. Moreover, it is shown that the developed model has the potential to correct the ocean tide loading effect in geodetic data more efficiently than the model of Foreman et al. (2000), especially around Glacier Bay.     

测边控制网的精度分析及应用

通过对测边控制网精度严密的估算和实例分析,从理论和实践上皆证明,经过精心的设计和施测前的仪器、设备细致而周密的检校,测边控制网的精度能够满足平均边长较短的精密控制网的要求,并且相对于其他网型的控制网有其显著的效率优势和灵活的布网优势。     

侧扫声纳和多波束测深系统组合探测海底目标

介绍了侧扫声纳和多波束测深系统的特点,通过实例说明了侧扫声纳和多波束测深系统在海洋目标探测中的综合应用。综合利用多波束测深系统测量数据和侧扫声纳声像图,可有效增强不同观测数据的互补性,提高工程质量。     

Comparison of existing poroelastic models for wave damping in a porous seabed

Mechanism of wave–seabed interaction has been extensively studied by coastal geotechnical engineers in recent years. Numerous poro-elastic models have been proposed to investigate the mechanism of wave propagation on a seabed in the past. The existing poro-elastic models include drained model, consolidation model, Coulomb-damping model, and full dynamic model. However, to date, the difference between the existing models is unclear. In this paper, the fully dynamic poro-elastic model for the wave–seabed interaction will be derived first. Then, the existing models will be reduced from the proposed fully dynamic model. Based on the numerical comparisons, the applicable range of each model is also clarified for the engineering practice.     

海洋调查中水下目标位置的确定

介绍了海洋调查中测量设备拖曳体(拖鱼)的三种定位方法：舷挂式、LAYBACK方式和超短基线方式;分析了不同定位方法确定水下目标位置的差异,并进行了精度估计。     

Introduction of a new friction routine into the SWAN model that evaluates roughness due to bedform and sediment size changes

The significant loss of wave energy due to seabed interaction in finite depths is a known effect and bottom friction terms are used in the wave models to account for this dissipation. In this paper, a new bottom-interaction function is tested by means of the SWAN model, based on measurements at two field sites, Lake George and Lakes Entrance, both in Australia. The function accounts for dependence of the friction on the formation process of bottom ripples and on the grain size of the sediment. The overall improvement of the model prediction both for the wave height and wave period is demonstrated.     

海洋地球物理探测技术及其在近海工程中的应用

介绍了多波束测深、侧扫声纳测深、浅地层剖面测量、高分辨率地震测量和海洋磁力测量等五项海洋地球物理探测技术的最新进展和简单工作原理,给出了目前国内外广泛使用的主要技术产品型号以及主要参数和性能和展示了这些技术近年来在近海工程,例如海缆（海底光缆、电缆和管线等）路由调查、跨海大桥和海底隧道工程地质环境评价、工程灾害因素分析、海底目标物寻找和水下考古等方面的应用实例。