The purpose of this study is to investigate, by means of field measurement, crack, unevenness, compressive strength and tilt of aged concrete armored coastal dikes constructed more than 40 years ago. It is revealed that cracks on the crown armoring of dike are classified into eight patterns and the probability of crack occurrence on the crown armoring is about 0.39, which is higher than those of the seaward and landward slopes armoring of dike. The maximum crack-widening speed per year after construction is about 0.32cm on the crown armoring and about 0.17cm on the landward slope armoring.
It goes without saying that the shore protection facility is a powerful countermeasure to protect the low coastal flatland from storm surge-caused disasters. In Japan, many shore protection facilities have been rapidly constructed since 1954~1960 at which severe storm surge disasters were caused by the successive attack of huge Typhoons of No.13 in 1953 and No.15 in 1959, and lifecycle management of coastal dikes is currently requested for making their life span as longer as possible. As of 2000 year, 68% of total coastal dikes constructed along Japanese coastal line are more than 30 years old and 46% of them are more than 40 years old (Nanba et al., 2003). It is well known in Japan that many mound-type coastal dikes aged more than 40 years old are situated in the low flatland area along semi-closed Ise-Bay and Mikawa-Bay connected to the Pacific Ocean. In order to maintain the design function of coastal dike as longer as possible and to repair or reconstruct economically, the actual condition of aged and deteriorated coastal dikes concerning to cracks, compressive strength of armored concrete, unevenness of the coastal dike should be known as accurately as possible.
