Improvement in transmission experiment of elastic waves through partially saturated porous sand soil
Abstract
In contrast to rock samples, for more highly porous and unconsolidated media, it is still veiled how propagation characteristics of transmitting elastic waves are effected by degrees of deformation and water saturation. Nakayama et al. (2016, AGU) tried to investigate spatio-temporal variations in spectral amplitudes of transmitting waves through a highly porous and unconsolidated sand soil during water injection in laboratory. However, a relationship between spectral amplitudes of transmitting waves and degree of water saturation was not cleared because the spectral amplitudes varied complicatedly while the sand soil became saturated. We tried to carry out some element tests about our measurement methods to reveal the causes of the complicated spectral amplitude variations. It is possible that the displacement of the vibration point of the shaker was so large that the medium in the vicinity of the shaker deformed plastically. In addition, we could not estimate variations of phase velocities due to the low reproducibility of the sweep signals. In this study, we used a new shaker, which had a small displacement of its vibration point and a small effect on plastic deformation of the vicinity of it, and investigated the reproducibility of signals output from the shaker and a function generator (FG) adopted signals to the shaker. First, we designed an ideal arbitrary waveform whose initial phase was zero (zero offsets including a sweep signal (1-6 kHz)). We repeatedly adopted the waveform to an FG and recorded them. Second, we attached an accelerometer onto the vibration point of the shaker, and recorded signals output from the shaker in the same measurement system. In these results, the recorded individual waveforms were similar each other (Figure 1). We succeeded in getting highly-reproducible signals. Acknowledgment: This work is supported by JSPS KAKENHI Grant Numbers JP15H02996 and 26750135.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMNS41A0009N
- Keywords:
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- 1826 Geomorphology: hillslope;
- HYDROLOGY;
- 1835 Hydrogeophysics;
- HYDROLOGY;
- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4341 Early warning systems;
- NATURAL HAZARDS