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Tomita T.,Port and Airport Research Institute | Takahashi K.,Penta Ocean Construction Co.
Proceedings of the Coastal Engineering Conference | Year: 2014

The 2011 Tohoku tsunami hitting Kuji port, Japan, was high whose height of 5.4 m was measured in the water area of 49.5 m deep in front of the open mouth of the port. This tsunami was accompanied by short-period waves while it propagated in the port, and then it broke in the port of 18 m deep approximately ahead on a breakwater. Since wave pressure by a tsunami with short-period waves is important for design of breakwaters according to Ikeno et al. (2006), such wave transformation and deformation should be able to be calculated for planning and designing measures to save people and reduce property loss. In this study, a non-hydrostatic mathematical model was developed to calculate tsunamis including short period waves, and validated in comparison with experimental results in which the tsunami in Kuji port was modeled. Source

Neupane D.,Ehime University | Yasuhara H.,Ehime University | Kinoshita N.,Ehime University | Unno T.,Penta Ocean Construction Co.
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

A grouting technique for enzymatic calcite precipitation is evaluated. Urea and calcium salt, at various concentrations, are mixed with a concentration-fixed enzyme to obtain the optimal precipitation of CaCO3. The optimally combined solution is injected into sand samples in small PVC cylinders. Then, the improvement in small-scale samples is observed. The combination, approved for small-scale tests, is further used for larger-scale tests. The porosity distribution within the soil is evaluated by sampling the treated sand at different locations. A precipitation ratio up to 80% can be obtained using a small amount of the enzyme. The results show that the in situ enzymatic CaCO3 precipitation technique may be feasible for use in larger-scale applications. A multiphysics simulator that considers the calcite precipitation reaction during the transport of the solution is adopted to predict the evolution of the porosity. The predicted porosities are compared with the measured porosities. The results show that the numerical predictions can replicate the actual changes in porosity relatively well and that the numerical model should be helpful in assuming these changes caused by the precipitated CaCO3 induced by the grouting technique examined in this work. © 2013 American Society of Civil Engineers. Source

Watabe Y.,Port and Airport Research Institute | Saegusa H.,Toa Corporation | Shinsha H.,Penta Ocean Construction Co. | Tsuchida T.,Hiroshima University
Proceedings of the Institution of Civil Engineers: Ground Improvement | Year: 2011

Airfoam-treated lightweight soil is lightweight and provides for the early age development of shear strength and effective utilisation of dredged soils. This paper summarises a 10 year follow-up study of the lightweight soils that were placed as backfill at the seawall in Kobe Port Island and Tokyo International airport. These two sites are the early case examples of constructions undertaken in 1996 including the recovery project after the Kobe earthquake disaster and the offshore expansion project of the Tokyo International airport. Sampling and laboratory testing were carried out to investigate the physical and mechanical properties in order to compare the initial material condition. The depth profiles of the soil parameters such as bulk density, water content, pH, calcium content, shear strength, needle penetration resistance, compressive yield stress and compression index were examined. Consequently, it was confirmed that the physical and mechanical properties of the airfoam-treated lightweight soil satisfied their required performance criteria, indicating that the lightweight soil had sufficient durability for use as geomaterial for construction in coastal areas. Source

Sasaki J.,Yokohama National University | Komatsu Y.,Penta Ocean Construction Co. | Matsumaru R.,IRM Ltd | Wiyono R.U.A.,Yokohama National University
Journal of Coastal Research | Year: 2011

An unstructured-grid, finite-volume, 3D primitive equation coastal circulation model, FVCOM, was first slightly modified to apply to tsunami propagation and inundation problems in terms of the treatment of initial conditions. The model was applied to 2004 Indian Ocean Tsunami, focusing on propagation in Indian Ocean and inundation in Banda Aceh, Indonesia. Unstructured mesh was generated using fine Geographical Information System (GIS) datasets, covering Indian Ocean and inundation areas in Banda Aceh with a wide range of grid size from 50 km in the ocean to 5 m in Banda Aceh downtown on one grid system. The computed results are consistent with measured tidal gauges at Krabi and Kuraburi, Thailand, as well as at Ulee Lheue, Banda Aceh. Accuracy in reproducing inundation areas is highly enhanced after resolving fine structures of roads and buildings in downtown of Banda Aceh. Considering the recent progress in high resolution GIS datasets and computer resources, application of FVCOM will become an effective tool to consider management of local disaster prevention in a straightforward and easier manner. Source

Takaine T.,Asanuma Corporation | Tashiro M.,Nagoya University | Shiina T.,Penta Ocean Construction Co. | Noda T.,Nagoya University | Asaoka A.,Nagoya University
Soils and Foundations | Year: 2010

The continuous behaviour of a ground-embankment system from the stage of deformation up to failure was predicted with respect to an actual test embankment that had been constructed in stages on a soft ground made up of peat and calcareous soil. The behaviour prediction was carried out by employing soil-water coupled finite deformation analysis, which also included simulation of the embankment construction process. The information used in the analysis was limited to such things as the results of soil tests on soil materials (peat and calcareous soil) sampled from the ground, including their sensitivity ratios, and the embankment's construction history. The SYS Cam-clay model was used in the constitutive equations of the soils to determine the material constants of the soils and the initial conditions of the ground, and the computations were performed under plane strain conditions. As a result, the computed profiles of W-type ground settlement and of slip surfaces running through the embankment were found to be in good overall agreement with the actual profiles measured at the site. Furthermore, we found that this slippage is attributable to the undrained shear response of the soil elements in the calcareous soil layer, where slippage begins to occur during embankment loading. In other words, the slippage is caused by the rapid softening behaviour caused by the degradation of structure after the effective stress ratio reaches the vicinity of the critical state line. Source

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