Kuriyama Y.,Port and Airport Research Institute
Coastal Engineering | Year: 2012
A wave-averaged process-based one-dimensional model for beach profile change was developed to predict the cyclic evolution of longshore bars. The cross-shore sediment transport was assumed to be composed of suspended load due to wave breaking and bed load due to velocity skewness, acceleration skewness, and beach slope. The model's performance was investigated using the beach profile data obtained every weekday during a 12-year period from 1989 to 2000 along a 400-m long pier at the Hazaki Oceanographical Research Station, located on the Hasaki coast of Japan, where the mean duration of bar evolution is approximately 1. year. The model was unable to reproduce bar development from a rather flat profile, possibly because some sediment movement process was missing in the model. However, the model calibrated with a 1-year data set, including the bar evolution cycle consisting of bar generation, seaward migration, decay, and new bar generation, can be used to predict the first cycles of bar evolution at Hasaki. © 2011 Elsevier B.V.
Kitazume M.,Port and Airport Research Institute
Proceedings of the Institution of Civil Engineers: Ground Improvement | Year: 2011
The quality of deep-mixed soil (improved soil by in situ mixing) depends upon a number of factors including the type and condition of native soil, the type and amount of binder, and the production process. The quality assurance/ quality control (QA/QC) practice which focuses upon the quality of deep-mixed soil was originally established in Japan and Nordic countries and has been accepted worldwide for more than three decades. It comprises a laboratory mix test, field trial installation, monitoring and control of construction parameters during production and the verification by measuring the engineering characteristics of deep-mixed soil either by unconfined compression tests on core samples or by sounding. Diversification of application, soil type and execution system, together with the improved understanding on the behaviour of deep-mixed ground in the past two decades make it necessary for our profession to review the current QA/QC practice. Based on the literature review and the International collaborative study, the authors discussed the similarity and differences in the QA/QC procedures employed in different parts of the world and proposed the future research needs in a keynote lecture at Okinawa 2009 Deep Mixing Symposium. The current paper is a summary of this keynote address.
Kanno A.,Yamaguchi University |
Tanaka Y.,Port and Airport Research Institute
IEEE Geoscience and Remote Sensing Letters | Year: 2012
The multispectral method for the remote sensing of water depth proposed by Lyzenga et al. has been widely applied to shallow-water bathymetry by researchers. The predictor of water depth used in this method is a linear function of image-derived variables for each visible band. The coefficients of the predictor are estimated by using a number of pixels with known depth as training data; this depth information is usually obtained by performing in situ depthmeasurements. Theoretically, if an appropriate set of coefficients is chosen, the predictor can be insensitive to some variations in the optical properties of the bottom material and water. However, it is sensitive to variations in atmospheric and water surface transmittance and sun and satellite elevations. Consequently, a single set of coefficients cannot always be applied to multiple images. In this letter, we propose a simple method to estimate a general set of coefficients for Lyzenga's predictor that is relatively less affected by the aforementioned factors.We derive and utilize the theoretical fact that these factors affect only the intercept (constant term) of the predictor function. We demonstrate the effectiveness of the proposed method using WorldView-2 images of coral reefs. The proposed method will enable the application of a single set of coefficients (except for the intercept) to a broad range of images. This will significantly reduce the number of pixels with known depth required for the prediction of an image and thereby improve the feasibility of remote sensing of water depth. © 2012 IEEE.
Hirayama K.,Port and Airport Research Institute
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013
A nonlinear wave transformation model which can calculate the distribution of wave height inside a harbor with good accuracy has been used to estimate harbor tranquility. In a conventional procedure, however, the characteristics of such calculation could not be applied enough because the variation of wave height ratio with the steepness of incident waves would be ignored in prediction of an occurrence probability of wave height inside a harbor from one of offshore waves. In this paper, an appropriate procedure of harbor tranquility analysis for using a Boussinesq-type wave transformation model is proposed and its applicability is demonstrated in a harbor on coral reef topography. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).
Watabe Y.,Port and Airport Research Institute |
Yamada K.,Penta Ocean Construction Company Ltd |
Saitoh K.,Chuo University
Geotechnique | Year: 2011
In this study, a series of incremental loading oedometer tests and microscopic observations is carried out in order to investigate the influence of sand/bentonite fractions on hydraulic conductivity and compressibility. If sand particles do not form a skeletal structure, and each particle is independent in the clay matrix, an additive fraction of sand causes a decrease in the compressibility; however, it does not affect the hydraulic conductivity under the same consolidation pressure. The additive fraction of bentonite contributes to a decrease in the hydraulic conductivity, even for clayey materials. In addition, the relationship between the pore-size parameter, which represents the pore entrance size distribution, and the hydraulic conductivity is discussed using a probabilistic model known as the general capillary model.