Motoharu Jinguuji

Development of Multi-transmission High-speed Resistivity Survey System

A new resistivity survey system, which is capable of very fast data acquisition as compared with conventional DC resistivity systems, has been developed. The key characteristic to speed up the measurement is that the system transmits multiple currents of different frequencies from different transmitter electrodes simultaneously. Electric fields of these frequencies are separated in frequency domain at a receiver electrode and each transmitter electrode is identified by each respective frequency. The receiver electrodes are also multiple and simultaneously measured by using a multiple receiving function. The newly developed system has been successfully tested both with a water tank experiment in laboratory and by a 3D measurement at an experiment yard.

Blast Densification Method: Sound Propagation and Estimation of Psychological and Physical Effects

Experimental results on the propagation of blasting sounds from underground explosions for preventing liquefaction of ground are described. Psychological and physical effects of blasting sounds are estimated by comparison with previous studies on the effects and evaluation of continuous low-frequency sounds. The blasting sounds generated by underground explosions were impulsive low-frequency sounds, which predominantly involved frequencies of several Hz. Frequencies above 100 Hz tended to attenuate to a greater degree during propagation from the blasting area. Sound pressure levels at frequencies above 20 Hz exceeded the hearing threshold level as well as the threshold for rattling of building fittings for low-frequency sounds even at a point about 400 m distant from the blasting area. To predict the attenuation of the blasting sounds and estimate the appropriate distance for reducing the possibility of complaint, results of numerical calculations by the parabolic equation method together with meteorological data are shown.