Department of Civil Engineering, College of Science & Technology Nihon University Tokyo, JAPAN

takezawa@civil.cst.nihon-u.ac.jp

　

The concrete block-type breakwater is an effective work of beach erosion protections. Though it is desirable to have sources of littoral drift and abilities of accretions under normal waves in places where have to control the beach erosion, the beach erosion protection work has been almost constructed after the coast has been eroded by the abnormal waves in reality. The concrete block-type breakwater is able to expect effects of sediment and incident wave control. This paper describes on effect of concrete block-type breakwater obtained from experiments and some implementation examples. Model tests were carried out by a wave tank of length 20 m, width 10m, a depth of 0.7m and divided in two parts of width 5m by a vertical wall. One was the slope 1/15, and another was the slope 1/20. The sand of the median diameter 0.36 mm in fields was finished in slopes 1/15 and 1/20. A reduced scale of model was 1/50 according to the Froude similitude. And also, some implementation examples in fields are described in this paper. Conclusions are as follows:

　

¹Toyo Construction Co., Ltd. Hokkaido Branch Sapporo, JAPAN

tokikawa-kazuo@toyo-const.co.jp

　

²Port & Harbor Eng. Division Sapporo JAPAN

　

³University of Tokai Sapporo JAPAN

　

The summary of this paper is the Eco-reef concrete blocks have not only a characteristic for the wave force attenuations such as the wave shock-pressure, run-up and scouring the bed mound, but for the construction cost benefit to use an industrial scrape such as dredging mud or sand for the reef, just banking, and have a much contribution to the surrounding environment ecology. The block has been developed, with the mentioned merits, is a box-type and has some open slits on the walls.

　

The paper mentions the hydraulics characteristics of the artificial reef by the eco-reef concrete blocks, for the wave reflections, transmissions, set-up behind the reef, and the stability of the block to compare with the concrete armor unit or the rubble stones. The experiments are performed by the 2-dimensional wave tank (length: 22.0 m, width: 0.8 m, and depth: 2.0 m), with irregular wave generator. The weight of the model eco-reef block is around 1,100gr per each piece. The scale of the model is 1/30and1/25 for stability tests. The depth of the wave channel is 48 cm at the edge of the mound (8cm above the mound). The wave period are 2.0 sec and 2.8 sec, to find the optimum block's lines, to get a high stability, by changing the lines of the blocks. The rubble mounds are formed by using the Eco-reef blocks, concrete armor units and stones. The water depths are 6.7 cm and 13.3 cm on the mound, 40.0 cm and 46.6 cm at the edge of the mound with optimum block's lines. To make sure the hydraulics characteristics for the Eco-reef blocks, the wave reflections, transmissions, and set-up behind the reef are measured. Further, after banking a small mound such as the same rubble mounds behind the artificial reef with the Eco-reef blocks, the wave transmission are measured and analyzed the efficiency for the wave trans-missions attenuation.

　

　

Fooyin Institute of Technology Ta-Liao, Kao-Hsiung, TAIWAN

jtjuang@mail.fy.edu.tw

　

Submerged breakwater was the structures constructed of rubblemound normally and has a crest elevation below the local water level. They are well suited to the situation where minimal visual intrusion is desired and where it is desirable to maintain a moderate degree of energy transfer from the offshore to the shoreline region. However, there are benefits associated with the potential of smaller material requirements and have the ability to rehabilitate existing structures by reducing the incident wave energy with a submerged breakwater.

　

In this study, the wave runup theorem, proposed by Cross and Sollitt (1972), was used for analysis first. After that, based on the results of the wave runup test by irregular wave, the coefficients in the wave runup calculation of the runup water surface curve can be estimate. At the second, the computation method for the calculate of the wave energy loss coefficient in wave runup on step dyke as well as the energy loss of the incident wave pass over the submerged breakwater that proposed by Seabrook and Hall (1998) was quoted for the computation work. At last, by advantage of the result of the experiment of wave runup, a prediction model of the wave runup height was proposed. Comparison of the results of the predicted wave runup height that obtained by the proposed calculation model to the experiment coincided each other very well.

　

　

¹Nihon University Funabashi, Chiba, JAPAN

k04004@ocean.cst.nihon-u.ac.jp

k04003@ocean.cst.nihon-u.ac.jp

　

²National Fisheries Research Institute Fisheries Research Agency Kasima, Ibaraki, JAPAN

　

Today Japanese fishing industry has the problem that fishery-work people decrease. This cause is that Japanese fishing industry is aging and shortage of fresh people that keep away hard and dirty works. It is the solution to the problem to improve working environments in Japanese fishing industry. In minor research for ground works, I considered it as a purpose to make a reform point of working styles clear with research using OWAS.

　

An analysis with OWAS is the object for ground works for trawl fishery, purse seine fishery, fixed gill net fishery and shell dredge net fishery. The result to this analysis reveals that fishery people have some burdens with their backs and legs. I think that this cause is the difference of several floor levels in working space and the distance between working areas, and the weight of freights, and a burden of the body gets so high as they work longer.

　

Finally I am conceived that ways of working environment reform are to shorten several floor levels in working space and the distance between working areas and working hours, and to get burdens by using machines in works less.

　

　

Nishimatsu Construction Co., Ltd. Tokyo, JAPAN

HAGIWARA@ri.nishimatsu.co.jp

　

During the Hyogoken-Nambu earthquake in 1995, extensive liquefaction caused devastating damage to pile foundations of various kinds of structures. From the following site investigation, it was pointed out that foundations constructed near the waterfront should be designed taking into account the effect of the soil liquefaction during large earthquakes. On the other hand, to effectively response to rebel 2 seismic design method based on the performance design concept in Japan, there is an urgent need to investigate dynamic soil-structure interaction behavior over a wide range of strains such as post failure zone.

　

A series of shaking table tests was carried out on the pile foundations using a large shaking table under one gravitational field. Seismic responses of two-layered grounds and the pile foundations supporting an oil tank were obtained during a strong earthquake. The earthquake motion observed the 1995 Hyogoken-Nambu earthquake was used as the input motion, changing the maximum acceleration level up to 700 gal.

　

This paper discusses the correlation between the pore water pressures and the shear strain in the model ground, particularly focusing on an acceleration level. In addition, as the remedial measures against liquefaction, solidification beneath the oil tank was applied, by changing soil improvement area. It was found that the solidification method was able to effectively decrease the bending moments acting on the piles and mitigate ground deformations nearby the oil tank. Moreover, the tests results were simulated by FEM analysis under an axisymmetric condition. The FEM simulation was well consistent with the test results.