RIASSUNTO
Abstract:
This study reports on the results of the experiments on the arching condition of ice floes in the sea or rivers which have froze over. Knowing the conditions of arch formation by ice floes is valuable because the data can be used in deciding the span of bridges that will not form ice arches or by creating arches artificially in order to prevent invasion of ice. We built model bridge piers in a waterway and tested to see if arches are formed by changing (1) the proportion of water surface covered by model ice, (2) the span of bridge pier, (3) the pier''S shape of cross-section and nose shape (4) thickness of model ice, and (5) the fluid velocity. Also, we conducted another experiment using models of a different scale and compared the results. The results of the experiments showed the critical conditions of arch formation by ice floes. Also, as the results of experiment using two different scales agreed, the Froud Similitude was proved.
1. Introduction
Bridge piers constructed over the sea or rivers where the water freezes over are subject to various influences caused by the movement of ice floes. An ice jam might also work on the bridge pier as an ice force as well as a thrust-up force against the superstructure of the bridge. In addition, since an ice jam narrows the sectional-area of the river and accelerates the current velocity, the bridge pier will be scoured locally at the foundation. The arch formation of ice floes at the bridge piers is included as one of the factors which will lead to the formation of an ice jam. Saroma Lagoon in eastern Hokkaido is linked by a waterway to the Okhotsk Sea where drift ice occurs in winter.