Behavior of a Semi-Infinite Ice Cover under a Uniformly Moving Load

2018 ◽  
Keyword(s):  
Moving Load ◽  
Ice Cover

scholarly journals Увеличение ледоразрушающей способности изгибно-гравитационных волн при их приближении к берегу

2020 ◽  
Vol 44 (3) ◽  
pp. 37-45
Author(s):  
V. Kozin
Keyword(s):  
Gravitational Waves ◽  
Moving Load ◽  
Experimental Studies ◽  
Resonance Method ◽  
Free Edge ◽  
Ice Cover ◽  
General Information ◽  
Hydroelectric Power ◽  
Inland Waterways ◽  
Bending Stresses

Рассматривается возможность повышения эффективности резонансного метода разрушения ледяного покрова, т.е. путем возбуждения во льду резонансных изгибно-гравитационных волн амфибийными судами на воздушной подушке, при решении таких важных народнохозяйственных задач, как борьба с ледовыми осложнениями в виде заторов и зажоров на реках, текущих с юга на север; продление навигации на внутренних водных путях; раннее вскрытие ото льда водохранилищ на нижнем бьефе гидроэлектростанций с целью повышения их выработки электроэнергии и других задач за счет использования соответствующего маневрирования судов вблизи берега. Ввиду сложности процесса разрушения ледяного покрова из-за влияния на него близости берега в работе приведены только общие сведения по разрушению льда натурными судами на воздушной подушке в полевых условиях и результаты исследований, выполненных в опытовом бассейне на моделирующих ледяной покров упругих пленках. Показано, что использование такого маневра, как выход судна на берег во время выполнения ледокольных работ, может существенно повысить эффективность резонансного метода разрушения ледяного покрова, т.е. снизить энергозатраты на разрушение льда по сравнению с его реализацией в условиях бесконечного ледяного поля. Таким образом, было установлено, что в случаях, когда ледяной покров не удавалось разрушить при движении судов с резонансной скоростью (вес судна и давление в его воздушной подушке были недостаточными для разрушения льда данной толщины), то удавалось разрушить кромку льда при движении судна под углом к береговой линии с последующим выходом на берег. После чего, как показали результаты исследований, деформации ледяного покрова при последующем движении судов вдоль образовавшейся свободной кромки, а значит и изгибные напряжения во льду, существенно возрастали. В работе представлены результаты экспериментальных модельных исследований зависимости высоты изгибно-гравитационных волн, возбуждаемых в ледяном покрове движущейся нагрузкой, при выходе их на берег от угла наклона дна бассейна. Также приведены рекомендации по использованию угла наклона дна для повышения эффективности разрушения ледяного покрова (увеличения толщины разрушаемого льда) резонансным методом. Ключевые слова: ледяной покров, изгибно-гравитационные волны, движущаяся нагрузка, суда на воздушной подушке, резонансный метод, наклон дна. The paper considers the possibility of increasing the efficiency of the resonance method of ice cover destruction (RRL), i.e. by exciting resonant bending-gravitational waves (IGW) of an amphibious hovercraft (SVP) in solving such important economic problems as: clearance of ice complications in the form of congestion and blocking on rivers flowing from south to north; extension of navigation on inland waterways; early opening of ice reservoirs on the lower tail of hydroelectric power stations in order to increase their power generation, etc. through the use of appropriate maneuvering of vessels near the shore. Due to the complexity of the process of ice cover destruction due to the influence of the proximity of the coast on it, only general information on the destruction of ice from full-scale SVPs in the field and the results of studies carried out in an experimental pool on elastic films simulating ice cover are presented. As a result of research, deformation of the ice cover during the subsequent movement of vessels along the formed free edge, and hence the bending stresses in the ice, increased significantly. The paper presents the results of experimental studies of the dependence of the height of the IGW, excited in the ice cover by a moving load, when it comes ashore from the angle of inclination of the bottom of the pool. The recommendations on the use of the bottom angle to increase the efficiency of the destruction of the ice cover (increase the thickness of the destroyed ice) by the resonance method are also given. Keywords: ice cover, flexural-gravitational waves, wave height, hovercraft, destruction, resonance method, bottom tilt, modeling.

Unsteady deflection of ice cover in a frozen channel under a moving load

2019 ◽  
pp. 111-128
Author(s):  
Константин Александрович Шишмарев ◽  
Татьяна Ивановна Хабахпашева
Keyword(s):  
External Load ◽  
Rectangular Cross Section ◽  
Moving Load ◽  
Normal Modes ◽  
Viscoelastic Plate ◽  
Ice Cover ◽  
Stationary Problem ◽  
Local Pressure ◽  
Critical Speeds ◽  
Fluid Load

Рассмотрена нестационарная задача об изгибно-гравитационных волнах на поверхности замороженного ледового канала, вызванных движением внешней нагрузки. Задача решается методом преобразования Фурье вдоль канала и разложением прогибов льда по модам бегущих изгибно-гравитационных волн в канале. Предложен алгоритм, позволяющий привести решение, полученное с помощью обратного преобразования Фурье, к аналитическим формулам в виде суммы стационарных и нестационарных прогибов при конечных временах в системе координат, движущейся вместе с нагрузкой. Исследована эволюция прогибов во времени для разных скоростей движения нагрузки. Показано, что при увеличении времени решение для нестационарных прогибов ледовой пластины выходит на установившийся режим в системе координат, связанной с нагрузкой. Исследовано влияние коэффициента затухания на образование волн. The non-stationary problem of a moving external load along the surface of a frozen channel is studied in this paper. The channel has a rectangular cross section and is filled with an ideal fluid. The ice cover on the surface of the liquid is modelled by a thin elastic or viscoelastic plate (Kelvin-Voigt model), which is frozen to the channel walls. The external load is modelled by a local pressure moving at a constant speed along the channel. The ice-fluid-load system initially is at rest. The flow caused by both the moving load and the ice deflection is supposed to be potential. The problem is solved using the Fourier transform along the channel and by the method of normal modes. The presence of the channel walls and boundary conditions on them lead to an infinite (countable) number of dispersion relations and critical speeds for the hydroelastic waves propagating in the channel. Depending on the speed of the load, the form of the ice cover oscillations has one of two main cases. When the load moves at a speed lower than the first critical speed, the ice deflection is localised in the vicinity of the load. When the load is moving at supercritical speed, a system of hydroelastic waves propagating from the load is formed. The number of these wave systems is finite and depends on the relation of the speed of the load with the critical speeds for the channel. It is shown that as time increases, the solution for the ice deflection converge to a steady state in the coordinate system moving with the load. The influence of the retardation time on the formation of the ice deflections is investigated.

Seasonal variations in the properties and structural composition of sea ice and snow cover in the Bellingshausen and Amundsen Seas, Antarctica

1997 ◽  
Vol 43 (143) ◽  
pp. 138-151 ◽  
Author(s):  
M. O. Jeffries ◽  
K. Morris ◽  
W.F. Weeks ◽  
A. P. Worby
Keyword(s):  
Sea Ice ◽  
Isotopic Composition ◽  
Snow Cover ◽  
Sea Water ◽  
Ice Cores ◽  
Ice Cover ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Frazil Ice ◽  
Core Sets

AbstractSixty-three ice cores were collected in the Bellingshausen and Amundsen Seas in August and September 1993 during a cruise of the R.V. Nathaniel B. Palmer. The structure and stable-isotopic composition (18O/16O) of the cores were investigated in order to understand the growth conditions and to identify the key growth processes, particularly the contribution of snow to sea-ice formation. The structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the Bellingshausen Sea in March 1992 are reassessed. Frazil ice and congelation ice contribute 44% and 26%, respectively, to the composition of both the winter and summer ice-core sets, evidence that the relatively calm conditions that favour congelation-ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil-ice growth and pancake-ice formation. Both frazil- and congelation-ice layers have an av erage thickness of 0.12 m in winter, evidence that congelation ice and pancake ice thicken primarily by dynamic processes. The thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover. Snow-ice layers have a mean thickness of 0.20 and 0.28 m in the winter and summer cores, respectively, and the contribution of snow ice to the winter (24%) and summer (16%) core sets exceeds most quantities that have been reported previously in other Antarctic pack-ice zones. The thickness and quantity of snow ice may be due to a combination of high snow-accumulation rates and snow loads, environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow/ice interface, and bottom melting losses being compensated by snow-ice formation. Layers of superimposed ice at the top of each of the summer cores make up 4.6% of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice. The accumulation of superimposed ice is evidence that melting in the snow cover on Antarctic sea-ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass.

MODELING OF THE STRESS-STRAIN STATE OF A TRANSPORT TUNNEL UNDER LOAD AS A MEASURE TO REDUCE OPERATIONAL RISKS TO TRANSPORTATION FACILITIES

2020 ◽  
Vol 3 (8) ◽  
pp. 28-34
Author(s):  
N. V. IVANITSKAYA ◽  
◽  
A. K. BAYBULOV ◽  
M. V. SAFRONCHUK ◽  
◽  
...  
Keyword(s):  
Strain State ◽  
Moving Load ◽  
Element Model ◽  
Transport Infrastructure ◽  
Design Stage ◽  
Surface Load ◽  
Stress Strain ◽  
Stress Strain State ◽  
Operational Risks ◽  
Von Mises

In many countries economic policy has been paying increasing attention to the modernization and development of transport infrastructure as a measure of macroeconomic stimulation. Tunnels as an important component of transport infrastructure save a lot of logistical costs. It stimulates increasing freight and passenger traffic as well as the risks of the consequences of unforeseen overloads. The objective of the paper is to suggest the way to reduce operational risks of unforeseen moving load by modeling of the stress-strain state of a transport tunnel under growing load for different conditions and geophysical parameters. The article presents the results of a study of the stress-strain state (SSS) of a transport tunnel exposed to a mobile surface load. Numerical experiments carried out in the ANSYS software package made it possible to obtain diagrams showing the distribution of equivalent stresses (von Mises – stresses) according to the finite element model of the tunnel. The research results give grounds to assert that from external factors the stress state of the tunnel is mainly influenced by the distance to the moving load. The results obtained make it possible to predict in advance the parameters of the stress-strain state in the near-contour area of the tunnel and use the results in the subsequent design of underground facilities, as well as to increase their reliability and operational safety. This investigation gives an opportunity not only to reduce operational risks at the design stage, but to choose an optimal balance between investigation costs and benefits of safety usage period prolongation.

Beaufort Ambient Seismo-Acoustics Beneath Ice Cover (BASIC)

1993 ◽  
Author(s):  
Adam Schultz ◽  
Brian Lewis ◽  
Spahr Webb
Keyword(s):  
Ice Cover
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