Exploration Technology Using Cosmic Ray Muons for Engineering Geology

Abstract

In this study, we introduce some applicable results to the geophysical exploration of the cosmic rays muons as a technique to visualize internal density structure for underground and large structures. We have investigated the applicability of the exploration to a cavity in the ground, an internal structure of the nuclear reactor, a fractured zone and water level change of the reservoirs etc. in which have been applied to the depth from several meters to 300 meters. We investigate the measurement time by numerical computations and case study for cosmic ray muons exploration because the measurement time greatly varies by condition of the engineering geological application.

We estimated the measurement time when the covering depth, density of the soil and the zenith angle by the coincident measurement method of the conventional detector of 24.5cm in diameter and distance 140cm between the two detectors. As a result, for example, five days are approximately necessarily to detect the significant difference of the muons counting with density differences 0.2g/cm³ and the zenith angle less than 30 degrees with covering depth of 50m with the cavity of 5m in diameters.

In addition, we show the required measurement time is only 10 minutes per one measurement point by the omnidirectional measurement by the spherical detector of 24.5cm in diameter with the covering depth of 11m and cavity thickness of 3m.