Modified Moving Particle Semi-implicit methods for the prediction of 2D wave impact pressure

As a gridless particle method, the MPS (Moving Particle Semi-implicit) method has proven useful in a wide variety of engineering applications including free-surface hydrodynamic flows. Despite its wide range of applicability, the MPS method suffers from some shortcomings such as non-conservation of momentum and spurious pressure fluctuation. By introducing new formulations for the pressure gradient and a new formulation of the source term of the Poisson Pressure Equation (PPE), and by allowing a slight compressibility, we have proposed modified MPS methods for the prediction of wave impact pressure on a coastal structure. The improved performance of the modified methods is shown through the simulation of numerous wave impact problems (including the impacts by a dam break flow, a flip-through and two cases of slightly-breaking waves) in comparison with the experimental data.     

渤黄海沿海2月份海平面异常偏高成因分析

使用1980—2010年的水位、气温、海温、气压和风场资料,对中国渤黄海沿海2月份的海平面变化特征以及异常偏高成因进行了探讨,分析结果表明:近30年,渤黄海沿海2月份海平面呈现明显的上升趋势,2009年和2010年2月份的海平面达到近30年的高值,冬季高海平面导致全年平均海平面偏高。近两年2月份海平面处于多个长周期振动的高位重合期,各振幅叠加的结果近100 mm,对海平面起了明显的抬升作用。高海平面使得辽宁、河北以及山东等沿岸地区的海水入侵距离和土壤盐渍化程度均有所增加,海岸侵蚀加重;上海在2009—2010年连续2年2月份发生了近年较严重的咸潮入侵。2009年和2010年2月份,气压较常年同期显著偏低,冬季季风显著偏弱,是海平面上升的主要原因之一。     

Seismic Stability of Gravity Retaining Structures by Pseudo-Dynamic Method

An analytical expression of a gravity retaining wall's seismic stability against sliding and overturning is proposed in this article. The derivation, aiming at the cohesionless soil with inclined backfill surface and nonvertical wall back, is based on limit equilibrium analysis and the pseudo-dynamic method. The variations of the sliding and overturning stability safe factors with the horizontal seismic acceleration are investigated for different seismic amplification factors, soil friction angles, wall friction angles, vertical seismic acceleration coefficients, wall back inclination angles, and backfill surface inclination angles. The results indicate that the soil friction and horizontal seismic action significantly impact the seismic stability. The increase of vertical earthquake action changes the curvature of stability factor curves. The wall friction and back inclination strengthen the gravity retaining wall's resistance to sliding and overturning failure while the backfill surface inclination plays a negative role in the seismic stability. We also found that the seismic stability safe factors calculated by the proposed method are larger but more reasonable than those by the Mononobe-Okabe method.     

Prediction of impact pressure induced by breaking waves on vertical cylinders in random seas

This paper presents a method to statistically predict the magnitude of impact pressure (including extreme values) produced by deep water waves breaking on a circular cylinder representing a column of an ocean structure. Breaking waves defined here are not those whose tops are blown off by the wind but those whose breaking is associated with steepness. The probability density function of wave period associated with breaking waves is derived for a specified wave spectrum, and then converted to the probability density function of impact pressure. Impacts caused by two different breaking conditions are considered; one is the impact associated with waves breaking in close proximity to the column, the other is an impact caused by waves approaching the column after they have broken. As an example of the application of the present method, numerical computations are carried out for a wave spectrum obtained from measured data in the North Atlantic.     

高精度CTD剖面仪研制过程中的专用设备

本文介绍了“油水分离压力罐”的主要理论依据及该设备采用的特殊的机械结构，实践证明，利用该设备实现了在实验室条件下，模拟深海重力场检测CTD剖面仪中的某些关键传感器的目的。     

Multi-stakeholder collaboration yields valuable data for cetacean conservation in Gamba,Gabon

Private industry, the Government of Gabon and two international NGOs collaborated to conduct marine surveys off the coast of Gabon, Central Africa. Surveys addressed multiple objectives of surveillance and monitoring, the documentation of the distribution of and threats to the marine megafauna, and capacity-building among government agents and local early-career scientists. During 22 days of survey effort over a two-year period, observers documented humpback whales Megaptera novaeangliae, bottlenose dolphins Tursiops truncatus, Atlantic humpback dolphins Sousa teuszii and common dolphins Delphinus delphis. Humpback whale presence was limited to the months of July to November. Bottlenose dolphins were present year-round and photo-identification of individuals indicated a closed, resident population, with an abundance estimate of 118 (CV = 21.6%, 95% CI 78–180). Small open-decked fishing vessels with gillnets were observed concentrated around river mouths within 2 km of shore, while commercial trawlers were at least 10 km offshore; all were confirmed to be registered and legal. Observations of marine turtles, flocks of marine birds, and floating logs and other debris were sparse. This multi-stakeholder collaboration to conduct a marine survey can serve as an effective model by which funding and logistic support from private industry paired with technical expertise from NGOs and academic institutions can benefit marine and coastal conservation.     

基于旁压试验土体弹塑性本构模型初探

在大量旁压试验数据分析的基础上,通过曲线拟合,建立了旁压试验弹塑性阶段曲线的椭圆方程,利用土体SMP屈服准则和Rowe流动法则,推导出土体塑性阶段应力增量与应变增量间关系矩阵。在弹性阶段,假设土体应力-应变服从广义虎克定律,建立了基于旁压试验的土体弹塑性本构模型。编制了相应的计算程序,将文中模型计算结果与实际旁压试验曲线进行对比,初步验证了模型的正确性。将本构模型编译为ABAQUS自定义材料子程序UMAT,通过有限元对比分析,文中模型计算变形较弹性模型小,较摩尔-库仑模型大,与模型建立的假设一致。基于旁压试验的土体弹塑性本构模型参数少,且易于获取,便于在实际工程中应用。     

考虑拱效应深基坑支护结构土压力分析

针对基坑支护结构土压力的研究以数值模拟为主,而解析理论应用需要完善研究现状,提出一种用于计算基坑支护结构土压力的解析方法。根据填土中土拱效应的作用以及土拱成形的基本理论,结合极限平衡分析方法,应用摩尔圆理论确定了基坑端壁间稳定土拱的轨迹方程,并且得到基于土拱形状所围滑裂土体的体积,确定出基坑支护结构土压力的解析表达式,最后进行了算例分析,研究结果表明土体的物理属性决定了有效滑裂土体的边界。提出的解析方法是深基坑计算土压力的一种新的解析方法。     

采动煤岩渗透率演化模型及数值模拟

为描述采动煤岩渗透率演化过程,引入强度退化指数,基于Hoek-Brown强度准则,建立了考虑围压影响的煤岩应变软化力学本构模型。给出了体积应变和渗透率的关系方程,结合应变软化模型建立了采动煤岩渗透率演化模型,并在FLAC下予以实现。通过数值模拟研究了不同围压下圆柱岩样的峰后应变软化力学行为和某煤矿工作面开采过程中煤岩的渗透率演化过程,结果表明：（1）该模型能较好地反映围压对煤岩峰后应变软化行为的影响;（2）随着工作面推进,越来越多的煤岩单元破坏,渗透率也不断增长,逐渐成为瓦斯等流体运移的主要通道。（3）模型能再现采动煤岩渗透率演化的动态过程,从而为煤与瓦斯共采、煤层瓦斯抽放和瓦斯灾害防治提供指导。     

涡阳花沟区28-5煤田孔粘钻事故的处理实践

介绍了涡阳花沟区28-5煤田孔粘钻事故的原因和处理方法,加强对泥浆比重、滤失性和流变性能的调整,对预防孔内发生粘钻事故有积极作用。