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Research Papers

Qualitative Description of a Shoulder Ice Barrier-Ice Interaction During Model Tests

[+] Author and Article Information
Ada H. V. Repetto-Llamazares, Knut V. Høyland

Norwegian University of Technology
and Science,
NTNU, Trondheim, Norway

Arne Gürtner

Statoil,
Trondheim, Norway

Ove Tobias Gudmestad

University of Stavanger,
Stavanger, Norway

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received November 15, 2010; final manuscript received February 7, 2013; published online May 24, 2013. Assoc. Editor: Walter L. Kuehnlein.

J. Offshore Mech. Arct. Eng 135(3), 031501 (May 24, 2013) (7 pages) Paper No: OMAE-10-1108; doi: 10.1115/1.4023792 History: Received November 15, 2010; Revised February 07, 2013

This paper describes, qualitatively and through visual observations, the ice-sheet interaction with a shoulder ice barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters which are varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where the ice failure mode and shoulder performance are given special attention. The second part describes the phenomena observed in each particular experiment in more detail. The former analysis allows for the visual identification of three phases (as mentioned in previous publications) and gives a deeper insight into the characteristics of each phase. The latter analysis on the contrary, allows us to achieve interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the literature of full scale vertical and sloped structures, ice interaction with rubble accumulation, is performed. The similarities found in the study between the model and full scale observations lead us to assume that the observed model test behavior may be expected during ice-SIB interaction in full scale conditions. However, some events that could be associated with the problems of the model, such as ice scaling, are highlighted. As a conclusion regarding the SIB performance, it is shown that the shoulder section, which is the principal innovation of the concept, satisfactorily accomplishes its task and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding.

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Copyright © 2013 by ASME
Topics: Ice , Failure
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References

Figures

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Fig. 5

Accumulated rubble on the SIB and on the ice sheet

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Fig. 6

Underwater image showing the downward bending of the ice sheet due to failure of the ice by the weight of the rubble

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Fig. 7

Sequence of an ice block failing on the structure by passing through the accumulated rubble. The sequence shows the block falling towards the ice sheet.

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Fig. 4

Breaking of the ice pieces on the second slope (shoulder section)

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Fig. 3

Crack propagating from a side of the structure towards its center

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Fig. 2

(a) SIB placed on the underwater carriage and with the shallow water installed. (b) Side view of the SIB. The incoming ice and the process of the ice-SIB interaction are depicted model.

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Fig. 1

SIB placed in the large tank along with its basic dimensions in model scale

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Fig. 8

Top view of the SIB after finishing run 1100. It can be seen that the amount of ice that reached the shoulder section is small.

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Fig. 9

Grounding of the rubble in front of the central part of the SIB after finishing run 1200

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Fig. 10

(a) Top view of the SIB after finishing run 1300. (b) Grounding of the rubble in front of the central part of the SIB after finishing run 1300.

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Fig. 11

Side view of the SIB after runs. (a) 1400 and (b) 1300.

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Fig. 12

Longitudinal cracks during run 2100

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Fig. 13

Run 3100. (a) Initial stage in failure. (b) Side view of the rubble accumulation before. (c) After the “continuous-bending” started. (d) “Hull-shaped” ice rubble accumulation in front of the SIB. (e) Ice overriding the barrier as a “continuous-bended” ice sheet.

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Fig. 14

Example of the one-hinge mechanism with the secondary crack

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