排序方式： 共有22条查询结果，搜索用时 171 毫秒
1.
基于1∶1的大型水槽试验结果,分析了波浪溢流过程中位于海堤内坡的高性能加筋草皮护面的侵蚀特征。试验观察表明试验期间有一定土壤的损失,但护坡无明显的破坏;土面高度测量表明,当土壤流失发展到一定深度后,如果水动力强度变化不大,侵蚀趋于逐渐停止,这种现象称为侵蚀上限;结合试验现象对侵蚀上限进行了初步解释,并讨论了侵蚀上限达到前的侵蚀速率特征;植株密度监测表明,试验期间的草茎密度基本不变,草叶密度在开始几次试验期间持续减小,而后达到一个稳定值,这对于海堤的可持续防护有重要意义。研究成果能够为波浪溢流期间海堤内坡防御的相关研究和工程措施提供参考依据。 相似文献
2.
The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morphodynamic features in the area. A semi-enclosed rectangular basin with and without a coastal barrier was schematized from the topography of the Bohai Sea and Yellow Sea. The 2D tidal current field in this basin was simulated using the DELFT3D-FLOW model. The concept of tidal wave refraction, which highlights the effect of the sloped or stepped submarine topography on the propagation of the tidal waves, was introduced to explain the formation of the radial tidal current field. Under the effect of tidal wave refraction, co-phase lines of the counterclockwise rotating tidal wave and incident tidal wave are transformed into clockwise and counterclockwise deflections, respectively, leading to the convergence and divergence of the flow field. Regardless of whether a coastal barrier exists or not, the outer radial tidal current field might emerge over certain topography. The responses of the radial tidal current field in this basin to the environmental variations such as coastline changes and bottom erosions were discussed. Results show that local protrusion near the focal point of the radial tidal current field will have limited effects on the location of the tidal system. However, a remarkable shift of the amphidromic point toward the entrance and central axis of this basin and a movement of the focal point of the radial tidal current field toward the entrance could be caused by the significant seaward coastline advance and submarine slope erosion. 相似文献
3.
4.
通过遥感、水文和水化学、综合物探、地质取样、钻探以及静力触探等多种调查手段与方法,首次在我国重点经济区——珠江三角洲的近岸开展了1∶10万比例尺海洋地质环境与地质灾害综合调查,对调查区水域的海水化学要素、环境质量、水动力、地形地貌、沉积物、浅地层结构、潜在地质灾害以及海底工程地质条件进行了综合分析与研究,对海洋地质环境进行了综合评价与预警,并对该区海洋开发和工程建设提出了建议。 相似文献
5.
根据广西北海近岸表层沉积物取样测试结果,通过统计方法分析了研究区表层沉积物粒度特征、重金属Cr分布及其相互关系。结果表明,Cr含量为5.2×10~(-6)~66.7×10~(-6),在不同沉积物显示出不同统计特征;由于波浪淘选作用,表层沉积物砂分布最为广泛,粒级主要在~0.5mm到~0.25mm之间;砂由于颗粒较粗,其粒级与Cr关系较为分散,但总体上仍然存在着线性关系,且随着粒级变细相关性提高。黏土质砂的粒级与Cr线性关系明显改善,吸附粒级拐点在~0.125mm至~0.063mm之间;Cr含量与分选和平均粒径为线性关系,与偏态、峰态为聚类关系,并划分出五类聚类类型;有机质随沉积物颗粒变细而升高,变化范围为0.02%~1.29%,在黏土质砂中与Cr为显著线性正相关,且高、低值分段拟合关系稳定。Cr/Org比值变化很大,在(43~419)×10~(-6)/%之间,高、低值段Cr与有机质关系均表现稳定。长石/石英比值为0.03~0.08表明化学风化尚在初级阶段,Cr与该比值的关系尚不明显;以最小二乘法线性拟合参数|k|·R~2来综合表示沉积物组分、成分和粒级对Cr之影响性,砂沉积物中以砂组分影响力最大,砂质黏土中,砂组分含量大为降低,有机质权重最高。 相似文献
6.
GPS在高空气象探测中的应用 总被引：1，自引：0，他引：1
1 GPS概述全球定位卫星系统简称GPS,由GPS卫星星座、地面站和用户接收机组成.共有21颗工作星和3颗备用星,卫星轨道倾角55度,卫星离地面约2万米.地面站包括主控站、监测站和注入站.用户接收机分大地测量型,导航型和授时型.无论是大地测量,还是导航或授时都涉及时间基准.GPS有精度很高的时基系统,这是GPS的核心.每个GPS卫星上都带有精度很高的原子钟,30万年误差不超过1秒.GPS采用了扩频通信技术,利用直接序列扩频可测无线电信号传播的时间延迟的特性,测量GPS卫星到用户接收机的伪距,建立GPS卫星到用户接收机的球面三角方程式.由于空中至少有四颗GPS卫 相似文献
7.
The phenomenon of wastewater discharged into coastal waters can be simplified as a turbulent jet under the effect of waves and currents. Previous studies have been carried out to investigate the jet behaviors under the current only or the wave only environment. To gain obtain better understanding of the jet behaviors in a realistic situation, a series of physical experiments on the initial dilution of a vertical round jet in the wavy cross-flow environment are conducted. The diluted processes of the jet are recorded by a high-resolution camcorder and the concentration fields of the jet are measured with a peristaltic suction pumping system. When the jet is discharged into the wavy cross-flow environment, a distinctive phenomenon, namely “effluent clouds”, is observed. According to the quantitative measurements, the jet width in the wavy cross-flow environment increases more significantly than that does in the cross-flow only environment, indicating that the waves impose a positive effect on the enhancement of jet initial dilution. In order to generalize the experimental findings, a comprehensive velocity scale ua and a characteristic length scale l are introduced. Through dimensional analysis, it is found that the dimensionless centerline concentration trajectories is in proportional to 1/3 power of the dimensionless downstream distance , and the dimensionless centerline dilution is proportional to the square of the dimensionless centerline trajectory . Several empirical equations are then derived by using the Froude number of cross-flow Frc as a reference coefficient. This paper provides a better understanding and new estimations of the jet initial dilution under the combined effect of waves and cross-flow current. 相似文献
8.
雷州半岛东岸地下水化学要素变化以及海水入侵特征 总被引：2，自引：0，他引：2
对位于雷州半岛东岸的测井进行小潮、大潮期取样测试,对数据进行整理分析。结果显示,化学要素含量及变化特征随潮期、测井位置而变化,J1测井具有离子含量高,变化幅度小,J2测井则具有含量相对要低,但变化剧烈的特征,与测井所处地质环境有关;Na+、Cl-为主导成分,要素平均含量序列遵循良好的指数率,J2测井HCO3-含量比J1测井要高,要素之间的相关性也明显要好;J1测井潮周期氯化物水质均为V类,J2测井为III～V类,Cl-、Br-、溶解性固体总量海水入侵等级均为IV等级,J2测井为I～IV等级,结合其它指标均表明地下水海水入侵明显。 相似文献
9.
基于"我国重点海岸带滨海环境地质调查与评价"项目,分析了广西典型岸段20 m以浅的海域表层沉积物和地貌类型及其分布特征,并在此基础上探讨了碎屑矿物含量和种类的分布、变化以及组合。研究结果表明:研究区水动力较强,作用方式多样,有近30种碎屑矿物,其中主要有石英、长石、钛铁矿、云母、锆石、黄铁矿以及海绿石等,重矿物较为丰富;自全新世早期海侵以来,研究区先后进入了浅海海湾相沉积环境,但碎屑矿物种类与之前基本相似,其含量变化是由于气候和海平面的波动而致;研究区碎屑矿物在以沉积物和地貌类型为单位的各类地质单元中,其含量和种类均有所不同,尤以重矿物的变异性最为突出;各研究区重矿物组合可分为2~3个亚分区,均反映出与沉积环境关系密切。结果表明,研究区碎屑物质主要源于周缘陆区风化剥蚀、海岸侵蚀和河流输入,碎屑物质具有陆源性。 相似文献
10.