Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Calculation of Circumferential of Crack of Ice Blocks Based on YOLACTJinyan Cai1, Li Zhou1*, Shifeng Ding1, Vladimir G. Tsuprik2, Alexander Bekker2

1 School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology
Zhenjiang, Jiangsu, China
2 School of Engineering, Far Eastern Federal University, Vladivostok, Russiabased ice observation technologies (Wanget al., 2017; Wu &Xu.,2017) have been rapidly developed on the basis of bank-based
observation of river ice information (Bourgault, 2008). With the sea ice
image obtained, it is important to quickly and accurately make thecomputer automatically obtain the characteristic parameters of sea ice
crack. Many scholars focused on model ice detection algorithms, e.g.,
to accurately identify the target of model ice in the picture and toaccurately extract the position coordinates of each model ice pixel inthe picture for image processing. As for extracting model ice targets,there are threshold segmentation, image detection, and semanticsegmentation. Zhang et al. (2012) converted a grayscale image into abinary image based on the grayscale of the image and selected athreshold to divide the image into an "object area" and a "backgroundarea" to identify ice and calculate the area of ice crushing. Redmon et al.
(2016) used YOLO and other target detection network frameworks toautomatically identify the type and location information of ice throughthe training model. Bolya et al. (2020) used instance segmentation
network framework such as YOLACT, which can segment the target
accurately to the pixel level. However, these methods can only obtainthe type, location information, and shape characteristics of sea ice, theycannot obtain the circumferential crack parameters.

ABSTRACT
Usually, level ice breaks with occurrence of circumferential crack, inorder to calculate the resulting ice action on marine structures, crack
size in terms of radius and open angle should be considered incircumferential crack method. Traditionally, the crack size is evaluatedby using empirical formulas. However, there exist some uncertainties
when selecting empirical parameters. Therefore, how to determine ice
crack deserves further study. Based on the physical characteristic thatthe circumferential crack is always parallel to the boundary of thecontact surface, this paper proposes an algorithm for calculating thecircumferential crack parameters by using YOLACT network, which isa kind of computer vision method. Ice blocks shown in images are
identified through the YOLACT network to generate mask. ThenGaussian blur and Canny operator are applied to detect the edge of themask, which could obtain the edge information of the ice blocks. The
edges of the ice blocks are fitted by arc to derive radius and open angleof circumferential crack. The results show that the accuracy ofidentified radius and open angle is up to 96.12% and 96.58%
respectively when neglecting small and non-regular ice blocks. Thismethod could provide precise input of crack size into circumferential
crack method when calculating ice forces, which is helpful to initialdesign of polar ships and offshore structures in cold regions.

KEY WORDS:

Circumferential cracks will occur when level ice interacts with the hull,
because the ice suffers from the compression in the vertical direction
and tension in the horizontal direction. Then Zhou et al. (2019) foundthat there will be circumferential cracks parallel to the contact surface
and radial cracks perpendicular to the contact surface. Based on thephysical phenomena, Wang (2001) proposed an algorithm for theinteraction of moving sea ice and fixed conical structures, in which thegeometrical shape of the floating ice generated by flat crushing isassumed to be sector-shaped. The angle of ice breaking sector and theice-breaking radius are calculated according to the empirical formula inreference. Su et al. (2011) studied the ice load of the icebreaker in theprocess of ice breaking. Zhou et al. (2019) used the circumferential
crack method to simulate the form of sea ice breaking, predicted thebreaking load, and modified the illustration of Arctic Sea ice failuremode. The traditional calculation method of circumferential crack
parameters mainly uses the empirical formula with errors. Because of
the high cost and long period, the measurement on-site will cause themelting of ice and affect the measurement results.

model ice identification; image processing; arc

fitting

INTRODUCTION
With the global climate changing and the continuous melting of Arctic
Sea ice, the opening of the Arctic channel has once again become a
topic of human focus. A key to opening the Arctic channel is theacquisition of sea ice information. On-site ice observation is usuallyaffected by poor weather conditions, which make it challenge to obtainaccurate results. Satellite remote sensing has the advantage of largescale observation; however, it is unable to identify small-scale features(Wang et al., 2020).
With the help of photography technologies and hardware equipment,
the ship-based (LU et al., 2008) and unmanned aerial vehicle (UAV)-

1369