Public Works Research Center

Tsukuba, Japan

Public Works Research Center

Tsukuba, Japan
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Miyata Y.,Japan National Defense Academy | Bathurst R.J.,Royal Military College of Canada | Konam T.,Okasan Livic Co. | Dobash K.,Public Works Research Center
Soils and Foundations | Year: 2010

The paper presents the results of three full-scale tests that were carried out to investigate the influence of transient flooding on the performance of multi-anchor reinforced soil walls (MAW). The walls were constructed to a height of 6 m and flooded from the front of the structures to about mid-height and then drained in two to four stages. The walls were constructed with three different sand soils varying with respect to permeability, fines content and shear strength. Earth pressures and anchor loads were monitored during the flooding and draining stages and in-situ anchor pullout tests were performed. The analysis of results showed that the wall facings were very permeable and thus prevented unbalanced hydrostatic or seepage forces from developing during drawdown that could increase anchor loads beyond drained condition values. The accuracy of the current PWRC (2002) analytical model to estimate anchor capacity of MAW systems was demonstrated to vary widely depending on soil type and whether the soil was flooded or drained. However, on the load side, the method proposed by Miyata et al. (2009) to predict anchor loads was judged to be more accurate than the current BS8006 (2005) and PWRC (2002) methods based on the mean and spread of bias statistics where bias is defined as the ratio of measured to predicted anchor load.


Miyahara L.,Coastal Engineering Laboratory Co. | Uda T.,Public Works Research Center | Serizawa M.,Coastal Engineering Laboratory Co.
Proceedings of the Coastal Engineering Conference | Year: 2014

When waves are incident to a sandy beach from two opposite directions, a cuspate foreland or a land-tied island may develop. A typical land-tied island can be seen offshore of Shodoshima Island in the Seto Inland Sea. Another example is Chiringashima Island located in the south part of Satsuma Peninsula, Kyushu. In both cases, the island and land are connected by an extremely slender sand bar that has been stably maintained for a long time, suggesting that it is stable against wave action from both sides of the sand bar. We developed a numerical model for predicting the elongation of a sand bar of a land-tied island using the BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept).


Serizawa M.,Coastal Engineering Laboratory Co. | Uda T.,Public Works Research Center | Miyahara S.,Coastal Engineering Laboratory Co.
Proceedings of the Coastal Engineering Conference | Year: 2014

On a flat shallow seabed, sand spits and cuspate forelands with rhythmic shapes may develop and a barrier island can elongate alongshore, which significantly differs from the beach changes on coasts facing a deep ocean. In this study, the interaction between two circular sandy islands on a flat shallow seabed owing to waves was investigated by numerical simulation, focusing on the wave-sheltering effect of the islands themselves. The topographic changes caused by the interaction between two sandy islands were predicted using the BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept).


Serizawa M.,Coastal Engineering Laboratory Co. | Uda T.,Public Works Research Center | Miyahara S.,Coastal Engineering Laboratory Co.
Procedia Engineering | Year: 2015

In a slender water body with a large aspect ratio, the angle of wind waves relative to the direction normal to the shoreline may exceed 45°, resulting in the emergence of cuspate forelands and the subdivision of a lake, because the fetch distance along the principal axis becomes large. The BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) was used to predict the segmentation of a rectangular lake by wind waves under the conditions with/without the construction of offshore breakwaters that reduce the fetch distance, together with the numerical simulation of the deformation of a circular lake when a straight seawall cutting off a part of the lake was constructed. © 2015 Published by Elsevier Ltd.


Uda T.,Public Works Research Center | Onaka S.,Chiyoda Corporation | Serizawa M.,Coastal Engineering Laboratory Co.
Procedia Engineering | Year: 2015

Beach changes near Pengambengan fishing port in the western part of Bali Island, Indonesia, were investigated by the analysis of satellite images and field observations. In this area, northwestward longshore sand transport prevails because of the oblique wave incidence from the Indian Ocean, and this longshore sand transport has been blocked by a fishing port breakwater, resulting in severe downcoast erosion. As a measure, a seawall has been constructed, instead of maintaining the continuity of the natural longshore sand transport. The adoption of this method caused further downcoast erosion. The sand bypassing method should be adopted to mitigate such erosion. © 2015 Published by Elsevier Ltd.


Ishikawa T.,Public Works Research Center | Uda T.,Public Works Research Center | San-Nami T.,Coastal Engineering Laboratory Co.
Procedia Engineering | Year: 2015

On a coral reef coast near Point Kin located in central Okinawa, a large-scale excavation of the sandy beach was carried out by the American armed forces after WWII and sandy beach disappeared. However, after the excavation, the sandy beach was rapidly recovered. In this study, the rate of sand supply from the reef was estimated on the basis of change in foreshore area after the excavation of the shoreline area by using aerial photographs. It was concluded that sand supply of 0.5-0.8 m3/m/yr could be anticipated in the long term. © 2015 Published by Elsevier Ltd.


Uda T.,Public Works Research Center | Serizawa M.,Coastal Engineering Laboratory Co. | Kumada T.,Laboratory of Aquatic Science Consultant Co. | Sakai K.,Public Works Research Center
Coastal Engineering | Year: 2010

The empirical bay shape model proposed by Hsu and Evans in 1989 for predicting the static planform of a pocket beach is expanded to enable the calculation of three-dimensional beach changes on a pocket beach with a seawall. The original formulation was developed on the basis of a second-order regression analysis. Unlike the one-line model of shoreline changes, the model of Hsu and Evans does not require repeated calculations of the wave field and shoreline position, because it was derived on the assumption of null sediment movement within a pocket beach in static equilibrium, hence without the need of applying the continuity condition of total sand volume in the calculation. The expanded model proposed by the present authors satisfies the total sand budget on a pocket beach, by taking into account the concept of depth change due to longshore sand transport. Model tests were carried out and the new model was further applied to the beach changes at Kemigawa on the northeast of Tokyo Bay in Chiba Prefecture, as well as at Oarai in Ibaraki Prefecture, Japan. On both locations, seawall has been installed as countermeasures against beach erosion, where wave sheltering effect of the main breakwater and beach changes in front of the seawall has also been observed. With this expansion, the present model can be applied to predict the three-dimensional beach changes on a coast with seawall on a pocket beach. © 2009 Elsevier B.V. All rights reserved.


Noshi Y.,Nihon University | Uda T.,Public Works Research Center
Proceedings of the Coastal Engineering Conference | Year: 2014

When beach changes occur owing to the imbalance of longshore sand transport, not only bathymétrie changes but also grain size changes occur, having an impact on the coastal environment. With the increase in the anthropogenic impact, such changes have been observed on many coasts. Here, the bathymetric changes and changes in grain size of seabed materials were investigated on the basis of a numerical simulation using the BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept), with northern Kujukuri Beach in Japan as the study area.


Kobayashi A.,Nihon University | Uda T.,Public Works Research Center | Noshi Y.,Nihon University
Procedia Engineering | Year: 2015

The impact of the removal of a river mouth bar as a measure against river mouth closure to the surrounding coasts was investigated, taking the Hota coast as an example. Also, on this coast, landfilling was extensively carried out to build a coastal road along the coastline, resulting in the narrowing of the natural sandy beach. These anthropogenic factors affected the overall shoreline on a pocket beach, devastating the natural coastal environment. We investigated the effects of these impacts using aerial photographs and field observations. © 2015 The Authors. Published by Elsevier Ltd.


Uda T.,Public Works Research Center
Procedia Engineering | Year: 2015

Lakeshore changes associated with the extension of an offshore breakwater in a lake were investigated, taking the Torigasaki cuspate foreland located on the south shore of Lake Shinji as an example. After the construction of an offshore breakwater to form a wave-shelter zone, a cuspate foreland was formed with shoreline recession on nearby coasts. The shoreline changes were investigated using aerial photographs, and the beach changes were reproduced using the BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept). The predicted and measured beach changes were in good agreement. © 2015 The Authors. Published by Elsevier Ltd.

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