1. INTRODUCTION（1。）.PDFVIP

179 AUTOMATION AND ROBOTICS OF UNDERWATER CONCRETING IN HUGE SCALE STEEL CAISSON, THE MAIN TOWER FOUNDATIONS OF THE AKASHI KAIKYO BRIDGE Satoshi Kashima, First Construction Bureau Construction Department Mitushige Sakamoto and Ryota Okada, First Construction Bureau Tarumi construction Office Honshu Shikoku Bridge Authority Kobe City, Hyogo Pref., Japan Takehisa Iho, 2P Substructure Construction JV Yoshitaka Nakagawa, 3P Substructure Construction JV Akashi Kaikyo Bridge Kobe City, Hyogo Pref., Japan SUMMARY Antiwashout underwater concrete totalling about 500,000 m3 in volume was placed for the two underwater foundations of the Akashi Kaikyo Bridge, to be the worlds longest suspension bridge when completed. Placing took a year under severe marine conditions with a maximum 8-knot tidal current and a maximum depth of 60 m. Because the concrete had to be placed in layers over the wide area of a steel caisson, which acts as the formwork, and under great depth, a cleaning robot to clean the undersea bedrock surface was used, production and placing of concrete was automated, and a construction joint treatment robot was used to obtain good quality concrete. 1. INTRODUCTION The Akashi Kaikyo Bridge, currently under construction, will be the worlds longest suspension bridge with a total length of 3,910 m (1,990 m center span) when completed in 1997. The two main tower foundations, shown in Fig. 1, are constructed in water where the maximum tidal current is 8 kt and the maximum depth 60 m. The construction method is as follows: First, excavation of underwater bedrock, second, installation of steel caisson, then concreting within the caisson to form the foundation. This is known as t