Direct determination of tidal levels for engineering applications based on biological observations     

S.C. Stiros  P.A. Pirazzoli 《Coastal Engineering》2008

The scarcity of tide gauges in a global scale and the variability of the tidal levels along contiguous coasts mainly due to changing hydrographic conditions make the determination of tidal levels, especially of the Mean Sea Level, not an easy task. Determination of such levels with a precision of about 10 cm, necessary for most coastal engineering works, is usually based on records of temporary tide gauges or on geomorphological techniques. In this paper we present an alternative approach permitting to accurately identify tidal levels with a precision suitable for civil engineering applications based on biological observations on rocky shores, including breakwaters and quays. More specifically, we present evidence that the biological zonation, i.e. the distribution of coastal species in well-defined sub-horizontal belts, is practically insensitive to seasonal and other small-scale fluctuations of the sea level and is clearly related to certain levels, mostly the Mean Low Water (MLW). This approach, somewhat similar to what has been used in the past (for instance for the determination of the geodetic vertical datum in the Republic of Venice, Italy, till approximately AD 1800), permits direct determination of the Mean Sea Level or of other tidal levels on the basis of biological observations without statistical analyses of tide-gauge records with an accuracy of 5–10 cm, especially in microtidal, low-energy coasts.  相似文献   

Effects of installation on the cyclic axial behaviour of suction buckets in sandy soils     

《Applied Ocean Research》2019

Suction buckets differ with their easy and cost-efficient installation technique from other foundation types for offshore wind turbines. For successful completion of their installation process, suction is essential, but the imposed seepage leads to the changes in states of the soil in and around the bucket. Especially, a loosening of soil inside the bucket affects the load carrying behaviour of bucket subjected to repetitive loading resulting from environmental conditions. In this study, the behaviour of buckets under cyclic axial compressive loads with considering a possible loosening and related changes in permeability of soil inside the bucket is investigated numerically. In the framework of finite element analysis, a fully coupled two-phase model and a hypoplastic constitutive model are used to describe the saturated sandy soil behaviour under repetitive loading. The porosity-permeability variation is taken into account by Kozeny–Carman relationship. Special attention is dedicated to load carrying behaviour of bucket top plate, inner and outer skirt as well as base and their changes resulting from a loosening of soil inside the bucket with variable aspect ratio. For this purpose, cyclic axial compressive loads which cause an attenuation and progressive failure of soil-bucket system response are considered. The main findings on the changes in load carrying behaviour of bucket are presented and discussed.  相似文献   

Wave energy conversion under constrained wave-by-wave impedance matching with amplitude and phase-match limits     

《Applied Ocean Research》2019

This paper investigates an approach to limit the fullness of ‘tuning’ provided by wave-by-wave impedance matching control of wave energy devices in irregular waves. A single analytical formulation based on the Lagrange multiplier approach of Evans [1] is used to limit the velocity amplitude while also limiting the closeness of the phase match between velocity and exciting force. The paper studies the effect of the present technique in concurrently limiting the device velocity and the required control/actuation force. Time domain application requires wave-profile prediction, which here is based on a deterministic propagation model. Also examined in the time domain is the effect of possible violation of the displacement constraint, which for many designs implies impacts at hard stops within the power take-off mechanism. Time domain simulations are carried out for a 2-body axisymmetric converter (with physical end-stops) in sea states reported for a site off the US east coast. It is found that the approach leads to effective power conversion in the less energetic sea states, while as desired, considerable muting of the optimal response is found in the larger sea states. Under the assumptions of this work, the end-stop collisions are found to have a minor effect on the power conversion. The present approach could be used to guide the design of power take-off systems so that their displacement stroke, maximum force, and resistive and reactive power limits are well-matched to the achievable performance of a given controlled primary energy converter.  相似文献   

Observation on height changes of chinese tide gauges by GPS     

LIU Genyou ZHU Yaozhong XU Houze ZHANG Weimin 《地球空间信息科学学报》2006,9(4):244-249

IntroductionBecause of global temperature rising and glacierthawing,the sea level has risen about 10-25 cmin the past century[1]. The sea level change isone of the main ai ms in global change monito-ring. Presently the basic tool used in sea levelmonitori…  相似文献   

利用GPS拖体在万山区域测量平均海面技术研究     

翟万林  朱建华  马超飞  樊小慧  闫龙浩  王贺  陈春涛 《海洋学报(英文版)》2020,42(5):123-132

Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val) the HY-2 altimeter and its follow-on satellites. In March 2018, an experiment has been conducted to determine the sea surface height(SSH) under the HY-2 A ground track(Pass No. 203). A GPS towing-body(GPS-TB) was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2 A altimeter satellite ground track. Three GPS reference stations, one tide gauge and a GPS buoy were placed in the research area, in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively. All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module. The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island. Then the sea surface of this area was interpolated by Arc GIS10.2 with ordinary Kriging method. The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby, which has an equivalent precision with the GPS buoy. The interpolated sea surface has a bias of –1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line. The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface(MSS). In the Cal/Val of satellites, the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.  相似文献   

类软土滑坡滑动带的确定   总被引：2，自引：1，他引：1  

朱宝龙  胡厚田  张玉芳  陈强  张胜文 《工程地质学报》2006,14(1):28-34

类软土是一种特殊意义上的软土,它与一般沉积软土比较,在形成原因、分布范围、物质组成等其他特性上有区别;由其构成的类软土滑坡则具有普通滑坡不具有的特征。以京珠高速粤南段K108类滑坡为例,介绍了滑坡的地层岩性、构造特征、水文地质特征;应用位移监测方法查明滑坡有五层滑动带,滑面成近于圆弧形的勺形,并对滑坡的产生原因及滑动过程进行了分析,得出降雨和边坡的开挖是导致滑坡的直接诱因。  相似文献   

潮汐测量与验潮技术的发展   总被引：10，自引：0，他引：10  

阮锐 《海洋技术学报》2001,20(3):68-71

潮汐是由各天体作用于地球上的引潮力所产生，不仅海洋中有潮汐，大气圈和地球固体部分也同样存在着潮汐。海道测量中的潮汐测量仅指海洋潮汐测量仅指海洋潮汐测量，潮汐测量的手段很多，主要包括采用水尺；浮子式、引压钟式、声学式、压力式验潮仪验潮。而GPS验潮及潮汐遥感测量等技术研究国内外正在开展。所有这些验潮技术各有自己的特点。  相似文献   

山东荣成湾月湖口门落潮干道的推移质输运   总被引：6，自引：2，他引：6  

薛允传  高抒  贾建军 《海洋与湖沼》2002,33(4):356-363

改进了Gao等 ( 1 994)方法 ,并用以计算潮汐汊道口门落潮干道的垂线平均流速。利用月湖潮汐汊道系统冬、夏季各一个月的潮位资料 ,计算落潮干道的潮流流速和推移质输运率。结果表明 ,流速的计算值和实测值呈良好的相关性 ,落潮干道内落潮流的输沙能力高于涨潮流输沙能力  相似文献   

近40年来珠江口的海平面变化   总被引：6，自引：0，他引：6  

时小军  陈特固  余克服 《海洋地质与第四纪地质》2008,28(1):127-134

利用大万山附近1°×1°经纬度网格的卫星高度计资料(1993—2006),计算出珠江口绝对海平面的上升速率为0·30±0·05cm/a,与由卫星高度计得出的全球平均海平面的上升速率一致。珠江口各验潮站近40年的潮位变化趋势分析表明,珠江口海平面正加速上升,为全球气候变暖所致;珠江口海平面与全球温度变化和ENSO活动密切相关,一般在ENSO年海平面相对较低。以IPCC有关全球温度上升幅度的预报值和海平面与全球温度变化的关系为依据,预计到2030和2050年珠江口绝对海平面将分别上升6～14和9～21cm,若考虑地面沉降以及波动值,珠江口部分岸段相对海平面将可能分别上升30和50cm。  相似文献   

2008年中国沿岸冬季寒潮激发陆架波的小波分析   总被引：1，自引：0，他引：1  

李君益  郑全安  胡建宇  范振华  朱佳  陈涛  朱本璐  徐莹 《海洋学报(英文版)》2015,34(11):22-31

This study applies the wavelet analysis to the tidal gauge records, alongshore winds, atmospheric temperature and pressure along the China coast in winter 2008. The analysis results show three events of sea level oscillations(SLOs) on the shelf induced by winter storms. The first event occurred from January 9 to 21. The SLO periods were double-peaked at 1.6–5.3 and 7.0–16.0 d with the power densities of 0.04–0.05 and 0.10–0.15 m2·d, respectively.The second event occurred from February 5 to 18. The SLO period was single-peaked at 2.3–3.5 d with power density of 0.03–0.04 m2·d. The third event occurred from February 20 to March 8. The SLO periods were doublepeaked at 1.5–4.3 and 6.1–8.2 d with the power densities of 0.08–0.11 and 0.02–0.08 m2·d, respectively. The SLOs propagated along the coast from Zhejiang in north to Guangdong in south. The phase speeds ranged about 9–29m/s from Kanmen to Pingtan, 5–11 m/s from Xiamen to Huizhou and 11–22 m/s from Huizhou to Shuidong. The dispersion relation of the SLOs shows their nature of coastal-trapped wave.  相似文献