A STUDY OF CRITICAL DEPTH AND MODE OF SAND MOVEMENT USING RADIOACTIVE GLASS SAND

Abstract

In Japan, in order to get fundamental data for harbor construction planning, radioactive glass sand has been used on the coasts of Tomakomai Irako, Fukue, Isohama, Kashima and Niigata as shown in Figure 1, The authors have directed these field experiments excepting Tomakomai and been doing model experiments using radioactive glass sand. The field observation of sand movement using radioactive tracers has been already performed in several countries of the world and many works have been published. Authors have aimed to make clear the direction of sand transport in several depths of water and the critical water depth of sand movement where harbors are to be constructed, in order to get basic data for the best arrangement of breakwaters on sandy beach. The activity of radioactive glass sand ( Co-60 and Sc-46 ) used at one point was several millicuries in the inland coast and several tens millicuries in the open coast. In this paper, the qualitative characteristics of sand movement in the offshore and the breaker zone and the relations of waves, depth and bottom materials are estimated from the field experiments. Moreover, in the model test, the glass sand containing Cr-51 was used in order to study the mode of sand movement due to waves, in particular, the direction of ripple movement and sand transport.