FREQUENCY DEPENDENT PROPERTY OF WAVES IN SATURATED SOIL

KlNYA MIURA , NOZOMU YOSHIDA and YOON SANG KIM

ABSTRACT Elastic wave propagation in saturated soil is investigated in order to grasp the frequency dependent wave propagation property of actual soil. First, a closed form solution of Biot's equation is derived under a one-directional wave propagation condition. Then, the frequency dependent properties of waves in various soils such as clay, silt, sand, gravel and soft rock are computed and discussed. The behavior is shown to be classified into three states: low frequency, high frequency and transient. Properties hardly change in the low and high frequency states. The degree of saturation is shown to hardly affect the shear wave property, but it greatly affects the dilatational wave property, especially in a highly saturated condition. Permeability hardly affects the properties at low and high frequency states, but it does change the frequency range of the transient state. Next, the applicability of Biot's formulation is examined and the high frequency state derived from Biot's equation is shown to be valid when permeability is larger than that of silt. Finally, it is shown that various mechanical properties can be evaluated using the frequency dependent characteristics of the wave, some of which are difficult to measure in situ with conventional tools.

Key words: attenuation, Biot's equation, coupled analysis, elastic wave, frequency, poro-elasticity, soil (IGC: E8/D8)