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Development of a numerical simulation model for suction rate using CADMAS-SURF
(2018-08-14)
Silarom, Kornvisith
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Yamamoto, Yoshimichi
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Yoshizawa, Syota
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Charusrojthanadech, Nunthawath
There are many cases where a coastal dike or a seawall constructed on a very shallow area was broken by a wave of a smaller height than the designed height. In many of these cases, the reason of the destruction was the suction phenomena. This phenomenon happens when waves reaches the front of the dike or the seawall, the wave pressure scours the front soil of the structure until it reaches the lowest edge of the structure followed by sucking of backfilling material of the structure. In this research, the authors proposed the numerical model which can calculate the suction rate with elapsed time by applying the pore water pressure and the flow velocity inside a dike or a seawall using "CADMAS-SURF". The authors proposed three coefficients for improving the calculated pressure from CADMAS-SURF. The reliability of the model was confirmed by reproducing the suction phenomena in Hirono Coast of Japan.
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Effect of jetties in northern part of coastal change at Chumphon estuary
(2018-01-01)
Promngam, Atsanupong
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Charusrojthanadech, Nunthawath
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Maleesee, Komsan
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Yamamoto, Yoshimichi
The research on the effect of coastal facilities for protecting an estuary from channel blockage and a coast from beach erosion by waves demands to understand wave propagation, a nearshore current and sediment transportation. The purpose of this research is to evaluate the effect of jetties to the Chumphon estuary coast in Chumphon province, Thailand, and propose measures for erosion protecting in this coast. The long term prediction by a one-line model indicates the heavy erosion of around 1000 m northward from the jetties, the erosion around 250 m and 650 m southward from the jetties. As for the erosion of around 250 m southward, measures were examined in the last inter-national conference of ISOPE. As for the erosion of around 650 m southward, since there is no property which should be protected, it is ignored here. Therefore, about the heavy erosion of around 1000 m northward, measures are examined. In this study, since almost of all sand must be transported to jetties, sand nourishment is not a good measure. Detached breakwaters, artificial reefs, and non-measures are examined with the costs on the construction or the compensation, and the prevention effect of wave overtopping, short term erosion, and deterioration of a view. It makes clear that the most effective measure is non-measures (in other words, it is “set back”).
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Analysis of coastal erosion in Khlong Wan Coast
(2017-01-01)
Silarom, Kornvisith
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Yamamoto, Yoshimichi
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Charusrojthanadech, Nunthawath
This research aims to investigate the effect which big coastal facilities exert on coastal erosion due to waves in Khlong Wan Coast and examine some measures. Field surveys and a long-term simulation with the one-line numerical model indicated that the blockage of silt-and-sand supply from the northeast side of the coast by a big groin and the blockage of the supply from the southwest side by a huge detached breakwater has caused coastal erosion. Moreover, because the prediction using the one-line model showed that the beach in the southwest side of an old fishing port will become the most dangerous area, some measures for the coastal protection were proposed. Then, examinations on topographical changes of the beach, wave overtopping rates, etc. elucidate that sand nourishment is the most effective measure.
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Effect of jetties in coastal change at chumphon estuary
(2017-01-01)
Promngam, Atsanupong
;
Charusrojthanadech, Nunthawath
;
Maleesee, Komsan
;
Yamamoto, Yoshimichi
The research on the effect of coastal facilities for protecting an estuary from channel blockage and a coast from beach erosion by waves demands to understand wave propagation, nearshore current and sediment transportation. The purpose of this research is to study theeffect of jetty and propose countermeasures to compensate insufficient safety in Chumphon estuary, Chumpon province. The field survey is executed, topographic maps, bathymetric data, wave data for storm surges, tidal data were collected and inputted in Ca's numerical model(Ca et. al., 2000). This model consists of the near shore fluid dynamicmodel based on the Boussinesq equation and the topographical change model which the bed load and the suspended load were considered. Although the jetties are very effective for channel maintenance, since diffraction waves by the jetties has drawn sand in the north-side beachof the jetties toward the jetties, serious coastal erosion has occurred in the center of this north-side beach. Moreover, according to thesimulation results by using Ca's model, in the south-side beach of thejetties, if a typhoon of Linda classes hits this area, since heavy overtopping occurs, wave dissipation facilities are necessary.
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Improvement of suction rate methods of backfilling materials from a coastal dike or a seawall
(2016-01-01)
Kuisorn, Wirayut
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Charusrojthanadech, Nunthawath
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Yamamoto, Yoshimichi
In recent, industrial behavior by humans has caused heavy coastal erosion, and the global warming is deteriorating the coastal safety. Therefore, the research on safety of a coastal dike and a seawall is becoming very important, and Ioroi, et al. presented two methods for predicting the suction rates of backfilling materials from those bodies because the main reason why those in the shallows are broken by small waves is the suction. In this paper, the authors improve their methods in order to raise the accuracy and consider the influence of uniformity coefficient and dry density of backfilling materials to the suction.
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Prediction of surface elevation change in mangrove forest and evaluation of coastal erosion prevention by mangrove forest
(2015-01-01)
Rattanarama, Puangpet
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Charusrojthanadech, Nunthawath
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Yamamoto, Yoshimichi
This research predicts the capacity of mangrove soil surfaces to increase in elevation in response to local wave. The characteristics of mangrove forest were investigated by field survey to consider between frequency and number of roots per tree, diameter of the circle range of roots, diameter of main boughs and diameter of roots longer than 1 m. The relation between wave transmission ratio (dissipated wave height/incident wave height) and tree density were analyzed. Then the simulation in 250m width of mangrove tree with transmission ratio 0.33 could evaluate the surface elevation change and had sufficient result of coastal erosion prevention by mangrove forest.
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Study on safety to a storm surge at Sangchan Beach
(2015-01-01)
Doungpan, Satawat
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Charusrojthanadech, Nunthawath
In the Sangchan beach, coastal erosion had occurred due to human's development till ten years ago. However, since many countermeasures (Y-type groins and detached breakwaters) were constructed, although this coastal erosion came to an end, the recovery of the beach is insufficient. Therefore, in this paper, the safety at the Sangchan beach by existing countermeasures is confirmed and some improvement plans for raising the safety to coastal disaster are examined. The numerical model of Ca et al. (2002) is used to evaluate the difference of coastal erosion between those plans to the present condition, and some famous equations are used to evaluate the difference of wave run-up heights and wave overtopping rates between those. As conclusion, the comprehensive comparison of examination results makes it clear that sand nourishment is the most proper countermeasure.
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Evaluation method of suction rate of backfilling materials from a coastal dike or a seawall
(2014-01-01)
Kuisorn, Wirayut
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Charusrojthanadech, Nunthawath
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Yamamoto, Yoshimichi
Evidence shows that coastal dikes and seawalls could be damaged or destroyed by coastal scours and the suction of backfilling materials. As the impacts of coastal erosion and global warming become severer, it is necessary to be able to predict the suction rate of backfilling materials from underneath a dike or a seawall with sufficient accuracy. Therefore, this research paper proposes a method that can predict the suction rate of backfilling materials from a dike or a seawall. The findings show that the estimates of the suction rate using the proposed method were very similar to the measured field data. This fact indicates that the proposed method can predict the rate of suction with sufficient accuracy. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).
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Examination of coastal erosion prevention in the back of the gulf of Thailand
(2013-09-16)
Charusrojthanadech, Nunthawath
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Rattanarama, Puangpet
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Yamamoto, Yoshimichi
The present work presents the effect of bamboo piles and geotextile bag structures on coastal erosion prevention. Simulations were performed to evaluate the wave transmission ratio and the erosion prevention effectiveness of the bamboo piles and geotextile bag using the numerical model of Ca, V. T. (2007), which has shown adequate accuracy in Yamamoto et al.s (2012). The study is the application of an advanced numerical model called Nearshore Wave Dynamics and Bottom Topography Change Simulation System (NWBSS), which is based on Boussinesq approximation equations for near-shore wave transformation and the continuity equation with a Crank-Nicholson scheme and Volume Of Fluid (VOF) technique. The numerical results of the prevention effectiveness in the case of the 43.75m wide bamboo pile wall are almost identical to those of the geotextile bag. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).
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Trial of an evaluation method of the building damage by Tsunami
(2012-06-01)
Charusrojthanadech, Nunthawath
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Yamamoto, Yoshimichi
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Ca, Vu Thanh
In order to develop a rational methodology to evaluate building damage caused by tsunamis, first, disaster data collected in Thailand, Sri Lanka, and Japan are introduced as verification data. Next, the applicability of an empirical method of predicting inundation depth (= the inundation height from ground level) based on analysis of those data and a numerical simulation method of tsunami flood is examined by comparing calculation values with the verification data. Then, the validity of a convenient method of evaluating building strength against the tsunami using the gate-type Rahmen Building Model is checked by comparing calculation results with actual damage and diagrams to get pillar widths or wall thicknesses at the breaking threshold for common sizes of buildings are proposed. © World Scientific Publishing Company.

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