Quasi-Saturated Soil and Its Research Directions

The term of quasi-saturated soil is not currently used in the literatures. However this type of soils is distributed extensively, such as the soils formulated by air sparging as a remediation technology for treatment of contaminated aquifers. In engineering, quasi-saturated soils are usually considered as saturated soils. Nevertheless the characteristic of quasi-saturated soils is very different from that of saturated soils. The differences are concluded as following: a) air bubbles block the pores so that the hydraulic conductivity decreases very much; b) the experiment model shows that the un-drained shear strength of quasi-saturated soils is higher than saturated soils; c) due to the compressibility of pore mixture fluid, the instant deformation occurs when the quasi-saturated soils are loaded; d) more time is needed to complete the consolidation of quasi-saturated soils when compared with saturated soil; e) the property of wave propagation in quasi-saturated soils differs from saturated soils and so on. In this paper, authors table some key questions about quasi-saturated soils firstly. Then according to the questions, the results or progress of research in quasi-saturated soils are introduced and summarized. Conclusions and recommendations for future research are addressed in the end: the research of quasi-saturated soils develops mainly around the effect of air bubbles.