Abstract
Cavities are caused by the deterioration of the social infrastructure inside the ground. As a result cave-in accidents occur. It may become the tragic incident such as occurrence of casualties. It is demanded that we prevent cavities in the ground before the cave-in occurs. Ground penetrating radar, seismic reflection survey and electric survey etc. are applied to explore the cavities inside the ground. However the geophysical exploration is not all-round about the exploration depth and resolution. Only gravity method or density logging is applied for the density of the ground. The exploration technology using cosmic ray muons can demand density distribution of the ground to support the needs for the cavity exploration. The muon telescope and the three-dimensional tomography technique are developed with the aim of geophysical exploration using cosmic ray muons to practical use as a method to make up for conventional geophysical exploration. In this paper, it is shown the principle of the exploration using muons, some result of the basic experiments and the feasibility for the engineering works.