, Typhoon No. 0418 (Typhoon Songda) moved north along the western coast of Hokkaido, bringing high winds to wide areas in the storm zone. Omori Bridge, a 429-m-long I-girder bridge on National Highway 229, suffered the collapse of a 159-m-long section. The bridge spanned a reef that is surrounded by wavedissipating blocks on the seaward side and precipices on the landward side. On the day of the collapse, waves were extremely high and winds were strong, and abnormal tide levels were attributed to the effect of the local topography. In this research, hydraulic model tests were performed to study the damage mechanism of the bridge and the wave forces that acted on it, in order to assess the safety of the truss bridge that will be erected for temporary restoration. The splash patterns were also examined to determine the conditions under which vehicles can safely run after the restoration.
In recent years, coastal erosion has emerged as a nationwide problem. Toward comprehensive sediment management that promotes coastal conservation, the mechanism of wide-area sediment transport needs to be understood. Research on sea sand drift has thus far targeted relatively shallow sea areas, such as the breaker zone. For wide-area sediment management, however, study should be extended to include the role of grain size in sand drift and to include sand drift in deep-sea areas. As part of this research, an field survey was conducted in the Ishikari coastal wide-area in winter, when significant wide-area topographical changes occur. As a result of the field survey in the outer breaker zone, a large sediment transport was found.
The HIROI formula, which estimates the wave forces, has been used in breakwater design for many years. As far as the authors know, significant wave height has been used for the HIROI formula in the past. The time when the formula was presented, however, was long before emergence of the concept of significant wave height. We verified the process of derivation of the formula by tracing back to the paper in which Dr. HIROI first presented the formula, studied the changes in wave height used for the formula and investigated the history of changes in the shape of breakwaters. As a result, we found that the highest wave height must be used for the HIROI formula , and that changes in breakwater structure existed behind the use of significant wave height in the formula .
Experimental study on soil deformation and stress within seabed during ice scour event Shinji KIOKA, Ryo Ishikawa, Atsushi KUBOUCHI and Hiroshi SAEKI.Ice-Scour Event is a phenomenon that occurs when deformed ice such as an ice ridge comes into contact with seabed. Ice-Scour has been reported to cause damage to communication cables and water intake pipelines. Although most of technical issues against the ice-scour have been focused on estimating the scour depth/burial depth, it will be also important to consider a sub-scour deformation, which means stress transmission or soil deformation within the seabed below the sea ice. I n this study, we carried out basic model experiments related to the sub-scour deformation by setting up some test conditions. We found that the stress within the seabed during ice-scouring does not depend on a drift speed of a model ice but an attack angle, and that the model ice with the smaller attack angle is though to cause the soil deformation of larger areas because of restriction/compression of a large amount of soil in front of inclined surface of an ice.
Ice-Scour Event is a phenomenon that occurs when deformed ice such as an ice ridge comes into contact with seabed.Ice-Scour has been reported to cause damage to communication cables and water intake pipelines. Our final goal is to develop the method for estimation of scour depth, or optimal depth of a buried structure such as a pipeline in order not to contact an ice keel.This paper reports on the application of the mechanical model that we had developed to field site. As a result of calculations using the model, orders similar to those in the field observation data-the scour length of several tens of meters to several kilometers and the scour depth of several tens of centimeters to several meters-were found. We also found that the interactions of pack ice/level ice surrounding an ice ridge as a driving force would greatly affect the performance of scour events.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.