Abstract
The laying-down caisson method was adopted to construct the bridge-pier foundation in deepsea such as Honshu-Shikoku connecting bridges.
To secure the quality of under-sea concrete and to prevent contamination of the ocean floor caused by leakage of mortar, it was necessary to seal the clearance between the rock-beds at the sea bottom and cutting edge of the bottom of the caisson without diver work.
Sponge-mat made of special polyurethane foam and special structure was used as the sealing material in constructing the large-scale caisson foundation such as the South Bisan-Seto bridge piers and so forth.
The present paper summarizes the development of the sealing material and its application to construction work.
