Effects of Confining Pressure and Degree of Saturation on Wave Velocities of Soils

AbstractMeasuring wave velocities of soils is a common methodology of determining the small-strain stiffness of soils. Both confining pressure and degree of saturation affect the magnitude of the wave velocities and hence the stiffness of the soil. However, confining pressure and degree of saturation affect P- and S-wave velocities of the soil differently. At full saturation, increases in effective confining pressure (σ′3) increase S-wave velocity, but P-wave velocity remains fairly constant. As the soil desaturates, the effects of net confining pressure (σ3 – ua) and matric suction (ua – uw) were observed to be different from the effect of effective confining pressure. This difference in response was investigated, and the results are reported here. Degree of saturation has been commonly associated with the Skempton’s pore-water pressure parameter B under an isotropic state of stress. However, some soils have a B-value less than 0.9 even at full saturation. In such cases, the P-wave velocity may be a bett...