FIELD INVESTIGATION ON SAND DRIFT AT PORT KASHD.IA FACING THE PACIFIC OCEAN

Shoji Sato, Norio Tanaka

Abstract


Port Kashima has been constructed since 1963 on the coast of Kashimanada located north-east of Tokyo. Fig. 1 is the general plan of Port Kashima showing the layout of breakwaters and inner basins. The length of south and north breakwaters will be 2,800 and 1,380 m, respectively. The depth of fairway will be 16 m below L.L.W.L. (lowest low water level) aiming to accomodate 100,000 ton class vessels. The coast of Kashimanada is a bowshaped sandy beach of some 70 km long facing the Pacific Ocean; Naka River flowed out at the north end and Tone River at the south end, as shown in Fig. 2. The northern portion has a narrow beach with the cliff of Kashima Plateau behind it and the southern portion is of alluvium zone by Tone River with the sand dunes. Port Kashima is being constructed at about 25 km north from the south end of Kashimanada Coast and this place is geologically called as the south alluvium zone. In the coast around Kashima Port, there runs a sand dune along the coast. The crest of this dune is about 8 m above L.L.W.L. in elevation. The back shore in front of the dune is 50-80 m in width and 3-4 m above L.L.W.L. in elevation. There are alongshore bars at 100-150 m seaward from the shore line on a usual day and at T00-400 m on a stormy day in beach profile. The bottom materials are composed of mainly fine sand and the mean spring tide range is about 1.4 m. The wave, large or small, attacks this coast every day. From the above-mentioned, the sand drift should be estimated to be remarkable at the constructing site of the harbor. Therefore, the field investigation concerning sand drift has been conducted since tow years before the beginning of the works of harbor construction. In this paper, a few recent investigations will be presented in detail, after a brief description of main field investigations conducted until 1965*

Keywords


field investigation; sand drift; Port Kashima

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