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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

Proposal on a new simple method for reproducing deformation processes of rubble mound profiles
Daiki Sakai
TOYO CONSTRUCTION CO.,LTD. TECHNICAL RESEARCH INSTITUTE
Naruohama, Nishinomiya, Hyogo, Japan

Gozo Tsujimoto
KUMAMOTO UNIVERSITY FACULTY OF ADVANCED SCIENCE AND TECHNOLOGY
Kurokami, Chuo-ku, KumamotoCity, Kumamoto, Japanand wave dissipating blocks are installed (Process b. in Figure 2). The
rubble mound is left bare between the two processes a and b. In thissituation, it is a problem that the rubble mound are damaged by highwaves caused by typhoons during construction. The restoration of therubble mound is a large backtracking and costly in terms of construction
cost and time. Therefore, it is necessary to take countermeasures toreduce damage to rubble mound, but these countermeasures cannot betaken unless the extent of damage is clarified. Therefore, it is important
to know the deformation characteristics of rubble mound during
construction. Hydraulic model experiments and numerical analysis are
considered as methods to study the damage of rubble mound. Sakai et al.
conducted hydraulic model tests on the damage process of rubble moundand clarified the damage mechanism as shown in Figure 3 (Sakai, 2019;Sakai, 2020). The damage to the top of the rubble mound by high waves
was mainly divided into offshore and onshore-side. The offshore damage
was caused by back wash, while the onshore-side damage was caused byswash. The damage to the shore side was especially pronounced, andmany stones on the top were carried to the shore with the passage of time.
Van der Meer et al.(Meer, 1994)carried out hydraulic model tests when
the top of the rubble mound was below the water surface, as did Sakai etal.(Sakai, 2019; Sakai, 2020), and found that the cross-sectional shape
was similar to that obtained by Sakai et al.(Sakai, 2019; Sakai, 2020). ToABSTRACT
In the construction of rubble mound, damages of the rubble moundcaused by high waves are the important issues. At construction sites, itis necessary to predict the extent of damage as soon as possible.
Therefore, the authors have been developing a numerical analysis
method with a small computational load. The authors focused on the factthat the failure process of rubble embankments was similar to theadvection-diffusion phenomenon. And then a one-dimensional
advection-diffusion equation is applied to reproduce the damage process
on the rubble mound. As a result, it was found that the diffusion
coefficient had the effect to changes of the top height and the advection
velocity the deformation toward the shore side.

KEY WORDS: Rubble mound; disaster process; hydraulic modelexperiments; simple numerical analysis; advection-diffusion equation;
moving and deformed form of rubble mound

INTRODUCTION
In reclamation to create a large area of land on the sea, such as a marine
airport, the out boundary is first enclosed by a rubble revetment, and thenthe inside of the rubble revetment is filled in. Figure 1 shows theconfiguration and construction procedure of the rubble mound. The firststep is to fill the area with sand and build a rubble mound on top of it.
After that, the superstructure is constructed on the rubble mound, and theoffshore slope of the rubble mound is covered with armor stones or armor
blocks. In some cases, wave dissipating blocks are installed. At the end,
the inside of the rubble mound is reclaimed to form the final shape. The
problem in this construction procedure is during or after the constructionof the rubble mound. The construction procedure of the reclamation isshown in Figure 2. In large-scale land reclamation , the construction ofsand cover and rubble mound is carried out first to enclose the outerboundary of the reclaimed land (Process a. in Figure 2). This is toprioritize the arrangement of construction vessels and the procurementof construction goods so that the entire process can proceed smoothly.
After the sand covering works and rubble mound is completed, the wave
dissipating blocks is constructed, armor stones or blocks are installed,

3. Coping

6. Reclamation

2. Rubble Mound
1. Sand covering
Fig. 1 Rubble mound configuration and construction procedure

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