Suction of Some Polyethylene Glycols Commonly Used for Unsaturated Soil Testing

摘要

In the laboratory, solutions of polyethylene glycols (PEGs) are used to control and apply suction in soils using the osmotic technique. In this study, the suctions of PEGs with molecular weights (M_r) of 1500, 4000, 6000, and 20 000 were measured at 25℃ using the chilled-mirror dew-point technique. The mass ratio of PEG-water mixtures was varied between 0.09 to 1.09 g of PEG/g of water to cover a wide range of suction from 0.09 MPa to 12.2 MPa. The results showed that, in general, PEGs with low M_r generated greater suctions than those with higher M_r. The difference between suctions of PEGs 6000 and 20000 was found to be minor. Concurrent with previous reports, analysis of the test results in terms of molality and molarity versus suction showed that PEGs with high M_r generated greater suctions than those with lower M_r. For any PEG, both molal and molar concentrations tend to generate similar suctions at low concentrations, whereas the density effect of PEG-water mixtures was found to be significant at high concentrations in that suctions corresponding to molar concentrations were far greater than their molal series counterparts. In general, good agreements were noted between the suctions measured in this study and those reported in the literature for similar PEG types. New equations were proposed that independently related mass ratio, molality, and molarity to suction of the PEGs studied. Additionally, relationships were established between the measured % Brix values and suctions of the PEGs studied.