Experimental Study of Sound Waves in Sandy Sediment

摘要

This dissertation describes experiments intended to help understand the physics of sound (compressional waves) propagating through sandy sediments (unconsolidated porous media). The theory (using a lumped parameter model) and measurements (using a reflection ratio technique) includes derivations and measurements of acoustic impedance, effective densities, wave speeds (phase velocities), effective pressures, mode shapes, pressure reflection coefficients, and material moduli. The results show the acoustic impedance divided by the phase velocity, rendering an 'effective density,' is less than the total density of the sediment (effective density 89% plus or minus 3% of total). The results also show the fluid in the sediment oscillates back-and-forth 2.2 plus or minus 0.4 times farther than the sand in the sediment (mode shape) during the passing of a sound wave. These facts suggest the existence of Biot waves (two compressional waves) in water- saturated sand.