A model study of the summer Southeast Vietnam Offshore Current in the southern South China Sea

The western boundary current in the southern South China Sea (SCS) in summer does not always flow northward along the Indo-China Peninsula, it leaves the southeast coast of peninsula around 10–14°N, forming a strong eastward jet called “Vietnam Coastal Current” or “Southeast Vietnam Offshore Current” (SVOC). It is known that the wind stress curl is the major driving factor responsible for this current. In this paper, we carry on the study of the separation position, strength and forming time of this current. A connected single-layer/two-layer model is employed here to study these problems. According to the numerical experiments and analyses of the vorticity dynamics, it is found that, the local wind stress curl (including the northern cyclonic and the southern anticyclonic wind forcing curl), the nonlinear term, the topographic effect, the planetary vorticity advection and the water exchange between the SCS and Java Sea via the Sunda Shelf have an important effect on both the position where this current leaves the coast and its strength; when there is an inflow via the Sunda Shelf, the current is stronger and the separation position is more northward; whereas the water stratification, the coastline and the inflow of Kuroshio have little effect on its separation. In fact, two opposite flowing currents, the northward SVOC and the southward western branch of the cyclonic eddy to its north near the Indo-China Peninsula, collide with each other, and the strength of these two currents determine the separation position of the SVOC. Origin of the SVOC may be driven by the local negative wind stress curl in the middle SCS in mid-spring, this current flows along the coast of the Indo-China Peninsula and leaves the coast at high latitude, flowing northeastward; once the local positive wind stress curl near the northern Indo-China Peninsula or the negative one near the southern Indo-China Peninsula is large enough, this current will begin to leave the coast at low latitude.     

埋地管道在地震行波作用下反应综述

埋地管道是"生命线地震工程"的重要组成部分,关系到震区人民的生活和震后救灾活动的开展。在地震行波作用下,其受力和破坏情况比较复杂,因此针对埋地管道采用合理可靠的地震反应分析方法至关重要。梳理了埋地管道在地震行波作用下解析理论和数值模拟的研究成果,总结了相关试验研究情况,指出了存在的问题和需要进一步改进的地方。     

Use of offshore wind farms to increase seismic resilience of Nuclear Power Plants

One of the challenges faced by the engineering profession is to meet the energy requirement of an increasingly prosperous world. Nuclear power was considered as a reliable option until the Fukushima Daiichi Nuclear Power Plant (NPP) disaster which eroded the public confidence. This short paper shows that offshore wind turbines (due to its shape and form, i.e. heavy rotating mass resting at the top of a tall tower) have long natural vibration periods (>3.0 s) and are less susceptible to earthquake dynamics. The performance of near-shore wind turbines structures during the 2011 Tohoku earthquake is reviewed. It has been observed that they performed well. As NPPs are often sited close to the sea, it is proposed that a small wind farm capable of supplying emergency backup power along with a NPP can be a better safety system (robust and resilient system) in avoiding cascading failures and catastrophic consequences.     

渤海海域沙三段烃源灶演化特征研究

烃源灶是表征供烃中心的最合适的方法, 其迁移演化研究对油气勘探具有重要意义. 渤海海域为渤海湾盆地海域部分, 是中国主要富油气盆地之一. 沙河街组三段是古近系4套烃源岩中最重要的烃源岩. 本文在沉积、构造发育和热史研究成果的基础之上, 结合烃源岩地球化学参数模拟计算了沙三段烃源岩成熟生烃及生、排烃演化历史, 并以此研究渤海海域沙三段烃源灶的演化特征. 结果表明研究区具有早期的双灶共存和晚期单灶为主, 多灶并存的特征, 即早期(古近纪)为岐口和渤中凹陷烃源灶; 晚期(新近纪至今)以渤中凹陷烃源灶为主, 岐口、南堡、黄河口、辽中、辽西和秦南凹陷等烃源灶并存. 烃源灶为油气田的形成提供了物质基础, 渤海海域的大中型油气田分布在主要烃源灶周围的凸起区和斜坡带. 因而, 本文的研究可以为渤海海域油气的深入勘探决策提供基础.     

城市地下综合管线质检系统设计与实现

针对城市地下综合管线普查数据量大、内容多、质量要求高等特点,传统的检查手段难以满足高效准确地开展质量检验的问题,本文分析了地下综合管线数据特点,探讨了该类成果质量检查内容与方法。提出了一种内外业一体化地下管线质检系统的构建方案。系统由基于平板的外业快速巡查子系统和基于算子集群的内业全自动化质检子系统组成,采用数据库管理模式,两个子系统可以无缝对接。应用表明,利用该系统可以有效提高质检的信息化程度,提升质检工作效率,保障检查结果的准确可靠。     

GPR在地下管线探测中的应用

论述了GPR探测地下管线的原理以及工程介质中电磁波的传播规律,结合工程实例,分析了地下管线在GPR图像上的基本特征,总结了GPR方法探测地下管线的一些关键.     

基于Autodesk MAP的管线GIS空间分析功能的实现

针对管线的地理分布特征,阐述了管线空间数据的拓扑结构,介绍了基于AutodeskMap实现管线空间分析的过程与方法,具体分析了管线图元的数据结构,解决了如何提取图元数据表中的特征数据的问题,实现了管线GIS的空间查询与统计分析功能。     

Morphodynamic and experimental assessments of wave theories in intermediate water depths

Although the near-bed, wave induced currents predicted by the various wave theories are responsible for seabed sediment transport, it is presently unclear which theory should be included in coastal geomorphic models. The theoretical expressions for near-bed, shorenormal flows are re-examined and the predictions are tested with morphodynamic and laboratory data. Five wave theories (Airy, Stokes, Cnoidal, Solitary, and Gerstner) are summarized here and arranged to predict the maximum onshore and offshore near-bed flows and the flow asymmetry as functions of the wave period, the wave height, and the water depth. Morphodynamic argument suggests that only Stokes and Cnoidal wave theories predict the asymmetry required to generate prototype seabed profiles in intermediate water depths. Laboratory measurements of wave induced near-bed flows are then reported and analysed. The results suggest that Stokes wave theory over-predicts the observed peak flows. A correction is derived which is shown to be analogous to the pressure attenuation corrections which are routinely applied to wave recording, seabed mounted transducer measurements.     

基于频谱补偿和数值模拟技术的江苏近海大气边界层百米高度处极端风速研究

在平均风速基本满足近海风力发电需求的前提下,近海大气边界层百米高度处极端风速的合理估算成为中国海上风电开发领域的研究热点。与低纬度海域台风极端风速的广泛研究不同,由于缺乏有效的技术手段,对于台风影响相对较少的中纬度海域,极端风速的科学认识明显不足。研究以江苏近海为例,通过频谱分析技术,定量刻画了数值模拟风速能谱在高频波段的能量衰减和截断特征;进而利用风速能谱曲线在频率域的积分及其在高频波段的补偿,实现无观测区域年最大风速的估算。与台风风场数值模拟技术相结合,综合考虑了中国中纬度海域受寒潮大风和热带气旋大风影响的复杂、特有气候特征,建立了一套可推广应用的近海大气边界层百米高度处极端风速估算的新方法。据此推算了江苏近海100 m高度处50年一遇的极端风速。结果表明:受寒潮大风影响,江苏北部海域的50年一遇风速超过40 m/s;少量北上的热带气旋则造成响水和如东附近海域40 m/s,甚至44 m/s以上的50年一遇风速;中部盐城附近海域的50年一遇风速则普遍低于35 m/s。研究成果不仅为该海域近海海洋工程的开发设计及安全运行提供重要的科学支撑,同时也有助于加深对中国极端气候事件的科学认识和大气边界层科学理论的发展。      

Response of single piles and pipelines in liquefaction-induced lateral spreads using controlled blasting

Two full-scale experiments using controlled blasting were conducted in the Port of Tokachi on Hokkaido Island, Japan, to assess the behavior of piles and pipelines subjected to lateral spreading. Test specimens were extensively instrumented with strain gauges to measure the distribution of moment during lateral spreading. This allowed us to compute the loading condition, as well as to conduct damage and performance assessments on the piles and pipelines. This paper presents the test results and discussions on the response of single piles and pipelines observed from the full-scale experiments. Based on the test results, it can be concluded that using controlled blasting successfully liquefied the soil, and subsequently induced lateral spreading. The movements of the single pile, as well as the transverse pipelines, were approximately the same as the free field soil movement. Observed moment distribution of the single pile indicated that global translation of the liquefied soil layer provided insignificant force to the pile. In addition, the degree of fixity at the pile tip significantly affected the moment along the pile as well as the pile head displacement. The pile with a higher degree of fixity at the pile tip had smaller pile head displacement but larger maximum moment.