Effects of Air Bubbles on B-Value and P-Wave Velocity of a Partly Saturated Sand.

Analysis of liquefaction susceptibility of nearly saturated sands

“…Equation (10) shows the variation of the equivalent bulk modulus of the pore fluid, B v , as a function of absolute pore fluid pressure, U, bulk modulus of water, B w , and the soil degree of saturation, S. Figure 1 shows the variation of B v /B w (bulk modulus ratio) with the degree of saturation for two different absolute pore pressures based on Equation (10). As it can be seen in this figure, the presence of air (even 1%, i.e.…”

“…Based on the assumption that surface tension effects are neglected, i.e. assuming the same absolute pressures for the pore fluid constituents (U a ¼ U w ¼ U) Koning [19] developed an expression for the equivalent bulk modulus of the air-water mixture (see A. JAFARI-MEHRABADI, M. A. ABDI AND R. POPESCU 694 also [10,20]). …”

“…The effects of transient air dissolution are neglected in this model. Tamura et al [10] showed that the effects of solubility and size of air bubbles on B-value and P-wave velocity of a partially saturated sand cannot be disregarded. Iveson [11] stated that the exact size and distribution of the air bubbles in a partially saturated soil is unknown.…”

“…So far not many theoretical studies have been performed for liquefaction susceptibility of partially saturated soils. Most of the proposed constitutive models such as the one presented by Pietruszczak and Pande [6,7] for partially saturated soils at high degrees of saturation are based on considering an equivalent bulk modulus for the mixture of gas and water [6][7][8][9][10]. Pietruszczak et al [8] used the proposed model by Pietruszczak and Pande [6,7] to perform numerical studies on partially saturated sand layers under seismic excitations.…”

Geotechnical Parameters from VP and VS Measurements in Unsaturated Soils

“…In such circumstances, in fact, air contained in the pores is present in the form of occluded bubbles that can be considered as one with pore water. In this connection, an accepted assumption is to retain the formal structure of Biot's theory, while introducing an appropriate bulk modulus for the water-air mixture (Ishihara, 1970;Kokusho, 2000;Tamura et al, 2002). Brutsaert (1964) was perhaps thê rst to develop a model for describing wave propagation through porous media saturated by two ‰uids.…”