Mechanism of Fracture of Concrete Canal Joints during the Niigataken Chuetsu-oki Earthquake

Abstract

Many concrete canal joints fractured during the Niigataken Chuetsu-oki Earthquake. Many of the fractures involved exfoliation of the concrete and cracks that extended from a water stop, and the presence of the water stop apparently affected those fractures. Breaking tests performed with specimens simulating a concrete canal joint were able to reproduce cracks similar to those found in the damaged canals. When cracks occurred in the tests, the concrete near the joint was displaced greatly, causing the specimen to open outward. The water stop was compressed, suggesting that lateral strain or bending pressure at which the water stop tried to bend occurred at the water stop, which forced the concrete to extend. As a result, cracks occurred near the water stop, splitting the specimen.