The study is subdivided into three phases: granular soils, cohesive soils, and field monitoring; the present paper addresses itself to the first phase of the overall project. Acoustic emissions are internally generated sounds that occur when a soil sample is stressed and subsequently deforms. The major conclusion of this research is that the acoustic emission response is directly related to this deformation and can be used in lieu of same in both laboratory and field situations. Other significant results as related to granular soils are the following: (1)Acoustic emission wave velocities are from 400fps-800fps (120m/s-240m/s); (2)acoustic emission frequencies range from 500 Hz - 8 kHz; (3)acoustic emission attenuation is strongly dependent on frequency and can be as high as 300dB/ft (10 dB/cm) at 16 kHz; (4)angular particles produce more emissions than rounded ones; (5)well-graded soils emit more acoustic emissions than poorly graded soils; and (6)particle size is not significant in the acoustic emission response.
Experts say that the "earth sound" may provide sufficient information to know in advance when it will follow a landslide. As the noise level increases, the soil parts become unstable and thus the measurement of the growth rate of the sound generated allows the prediction of landslides. Experts argue that a commercial version of a system of sensors that measure and analyze the acoustic behavior of the soil will be available in about two years.