Dynamic response of flexible retaining walls     

A. H. Younan  A. S. Veletsos 《地震工程与结构动力学》2000,29(12):1815-1844

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Factors influencing the removal of fine non-cohesive sediment by vortex settling basin at small river abstraction works     

Kuria Kiringu  Gerrit Basson 《国际泥沙研究》2021,36(4):501-511

Diverted sediment causes a wide range of problems at small diversion works.The difference in water levels between low flows and floods,low investment capital and presence of cohesive sediment and fine non-cohesive sediment coupled with a requirement for a high level of supply assurance makes the design of such hydraulic structures complex.Vortex settling basins(VSBs)offer a promising alternative to conventional settling structures or hydro-cyclones.In the current study,parameters affecting the trapping of particles>75 mm were numerically investigated using ANSYS Fluent and were validated by physical modeling.It was established that the inlet velocity needs to be maintained at 0.26 m/s,the underflow to inflow ratio should be between 0.05 and 0.10,the cylinder height to cylinder diameter ratio should be greater than 0.5,and the positioning of the inlet pipe to cylinder height ratio should be greater than 0.7,with a cone of slope ratio of 2:1(V:H)and the cylinder diameter to inlet diameter ratio should be 8.2.These parameters form the basic design guidelines for VSB use at small diversion works(<100 L/s duty capacity).  相似文献   

Three-Phase Secondary Migration of Hydrocarbon   总被引：1，自引：0，他引：1  

Hans Martin Helset  Larry W. Lake 《Mathematical Geology》1998,30(6):637-660

The objective of this work is to study the migration of hydrocarbons from a source rock into possible reservoirs. In particular, we consider simultaneous migration of gas and oil through a water-filled carrier bed and how this flow might result in characteristics that could be interpreted by nontraditional exploration methods. In the modeling, one-dimensional, immiscible, isothermal flow is assumed, and capillary effects are excluded. The seal is modeled as a layer of very low permeability. Our analysis is based on the method of characteristics and simple wave theory. Waves are changes in saturation(s) that move through a reservoir or carrier bed at a characteristic velocity. The analysis does not require capillary forces to trap hydrocarbons, but relies on nonlinear wave phenomena to explain migration and entrapment. No doubt, capillary forces are important in secondary migration and entrapment. Our treatment can be viewed as being part of a more complete theory on secondary migration, considering hydrodynamic effects here. We demonstrate that capillary forces are not the only mechanism that can cause trapping of hydrocarbons. We focus on the role of gas in the trapping of oil. If the seal is slightly permeable, some oil will flow through it. With gas present, the efficiency of the seal can increase, and oil can be completely trapped by a structure that would otherwise be permeable. For example, gas, being much more mobile than oil, can form a bank at the interface between two layers that have a modest permeability contrast. This gas bank will have a relatively large gas saturation. This will decrease the relative permeability to oil and completely trap subsequently migrated oil. Oil can also be trapped even when no gas bank is formed at the permeable seal. Features of this problem that might affect a seismic signal are (1) the existence of gas above (caused by a stow leakage of gas) and below a modest seal, (2) the gas leakage itself, (3) modest saturations in the oil column, and (4) overpressuring in the gas column.  相似文献   

物相之间氧同位素分馏的高温高压实验研究     

郑永飞  李一良 《地学前缘》1998,5(2):261-274

应用理论计算、实验测定和经验估计三种方法均能获取含固体矿物体系的氧同位素分馏系数,其中高温高压实验研究不仅能够得到物相之间的同位素平衡分馏系数,而且能够提供与同位素交换动力学和机理有关的信息。同位素分馏系数的实验校准方法已经由原来的两相体系（矿物Ｈ２Ｏ、矿物ＣＯ２和矿物ＣａＣＯ３）交换发展为三相体系（ＣａＣＯ３矿物流体）交换,化学合成、重结晶和矿物反应技术得到了进一步应用。本文评述了近十年来这一领域的研究进展,着重介绍了Ｈ２Ｏ、ＣＯ２和ＣａＣＯ３作为交换介质进行氧同位素分馏系数校准的技术原理和结果,探讨了热液和碳酸盐交换实验结果不一致的原因。  相似文献   

The influence of air and scale on wave impact pressures     

G. N. Bullock  A. R. Crawford  P. J. Hewson  M. J. A. Walkden  P. A. D. Bird 《Coastal Engineering》2001,42(4):417

Both laboratory and field tests that are described provide new information on the characteristics of wave impacts. Laboratory drop tests conducted using seawater and freshwater demonstrate that maximum impact pressures and rise times are influenced by both the level of aeration and the violence of the impact. A relationship is derived which enables the reduction in impact pressure caused by aeration to be estimated. This relationship is shown to provide a better means of predicting impact pressures in laboratory seawater wave tests from freshwater tests than either the Froude or Cauchy laws. Measurements are presented which show that, due to the different properties of seawater and freshwater, aeration levels are higher in seawater breakers than in freshwater breakers, even at a 1:25 model scale. The ways in which this affects the temporal variation in pressure and the scale relationships are discussed in some detail. Aeration and pressure measurements are also presented for full-scale wave impacts on a breakwater exposed to Atlantic waves. Attention is drawn to the likely role of expelled air and data included which indicate that the equivalent of up to 55% of entrained air does not necessarily prevent the occurrence of high impact pressures with short rise times.  相似文献   

Uplift Pressure of Waves on A Horizontal Plate   总被引：4，自引：0，他引：4  

周益人  陈国平  黄海龙  王登婷 《中国海洋工程》2003,17(3)

1 .IntroductionOwingtotheneedfordevelopingoffshoreresources,moreandmorehollow trussedstructuresareconstructed ,suchasalongshorequays ,islandquays,artificialislands ,bollards ,maritimeplatforms ,etc .Thelargeentitypartofthosemaritimestructuresusuallyconsistsofahorizontalplateabovethestillwaterlevel,anditusuallysuffersfromwaveattacksandthuscaneasilybedestroyed .Toavoidsuchakindofaccidents ,themostimportantistoaccuratelyevaluatetheupliftpressuresofwavesontheplateundervariouswaveconditionsandbound…  相似文献   

Sub aerial random wave pressure and layer thickness on impermeable sea walls     

S Neelamani 《Ocean Engineering》2004,31(13):1601-1621

Investigations on sub aerial wave pressures and layer thickness on plane impermeable and non-overtopping seawallns were carried out by using physical model studies. Seawalls with slopes of 1:3, 1:4 and 1:6 were used. JONSWAP spectrum with significant wave height, H_s from 0.08 to 0.2 m and peak periods, T_p from 1.5 to 6.0 s and a constant water depth of 0.7 m is used. Based on extensive measurements, empirical formulas for practical applications are proposed to predict the maximum, significant and mean sub aerial random wave pressure and layer thickness (thickness of water layer perpendicular to the still water level on the run-up zone) by using the surf similarity parameter, significant wave height and elevation on the sub aerial region as inputs. It is found that the maximum layer thickness is 1.11 times the significant layer thickness and maximum sub Arial wave pressure is 1.06 times the significant wave pressures. The predictive equations based on extensive measurements can be used for the design of non-overtopping seawalls.  相似文献   

Experimental investigation of pressure distribution on a cylinder due to the wave diffraction in a finite water depth     

Hakan Akyildiz 《Ocean Engineering》2002,29(9):1119-1132

The experimental investigations on the pressure distribution around a large vertical cylinder fixed on a wave channel, piercing the free surface and subjected to regular waves have been carried out. Recently, considerable advances have been made in the development of analytical techniques for studying non-linear wave loading phenomena on large structures. However, there is a lack of high quality experimental data that may be used for validating the analytical and numerical solutions obtained. This paper describes the design and execution of an experiment conducted at the Hydraulics Laboratory in the Civil Engineering Department of the Istanbul Technical University. Experimental measurements of pressures at different locations are presented including comparisons with the computational results. This study showed that the experimental and computational results generally exhibited better correlation, however, the measured pressure values diverged from the computational results while approaching the free surface.  相似文献   

油藏中CO_2矿物捕获能力研究     

杨慧心  李春先  于淼  张曙光  李轩  张颖  刘立 《世界地质》2016,35(4):1169-1177

利用TOUGHREACT软件,根据示范工程实验区大情字井的地层条件,针对含油及非含油储层哪一条件更适宜CO_2地质储存,设置了盐水组与含油组两组方案进行对比模拟。结果显示,含油组地层水中主要离子浓度及总矿化度低于盐水组,主要固碳矿物片钠铝石的生成量和CO_2的封存量明显小于盐水组。残余油的存在降低了矿物与水溶液进行离子交换的比表面积和储层的含水饱和度,并且占据矿物沉淀空间。尽管水岩作用受限,但油藏仍然可完成CO_2地质封存,且诸多优点表明油藏仍是CO_2地质封存的有利场所。  相似文献   

A Simple Limit Equilibrium Approach for Calculation of Ultimate Bearing Capacity of Shallow Foundations on Two-Layered Granular Soils     

Mahmoud Ghazavi  Amir Hossein Eghbali 《Geotechnical and Geological Engineering》2008,26(5):535-542

The bearing capacity of shallow foundations in a non-homogeneous soil profile has been a challenging task in geotechnical engineering. In this paper, a limit equilibrium method is used for calculating bearing capacity factors of shallow foundations constructed on a two-layered granular soil profile. The main objective has been to determine the ultimate bearing capacity computed from equivalent bearing capacity factors N_q and N_γ and comparing that with numerical analysis using finite element methods. It will be shown that the data obtained form the developed method are well comparable with those obtained from FE approach, specially when the difference between shear strength parameters of layers is low which is a practical case for sedimentary soil profiles and also for artificially compacted soils. A computer program has been developed to investigate the influence of various parameters on bearing capacity factors.  相似文献