Recently, we have taken a growing interest in the development of offshore placer minerals such as sand, black sand etc. in Japan. It seems that only a vibrocorer is a useful sampler to get a long and undisturbed core from unconsolidated placer deposit. Reports of the fundamental data to design a vibrocorer have not been published to date apparently, in spite ofne cessity of their data. To obtain the fundamental data, we carried out some basic studies and obtained the results as follows:
(1) it is comparatlvely easy to penetrate more than 5 meters of unconsolidated sand strata
(2) in this case, the whole weight of the vibrocorer, the force of vibration and the way of producing vibration are the effective factors,
(3) there exist the optimum values of these factors.
(4) under the conditions of the forces of vibration beeing kept same, the heavier the weight of the umbalanceis, the more rapid the penetrating rate is.
