| A new test method is proposed to measure the unfrozen water content in frozen soil. Each characteristic graph of unfrozen water is obtained by analyzing temperature-time history during freezing and thawing. The hysteresis of clay was be observed and analyzed by comparing its characteristic graphs of unfrozen water for freezing hand thawing. The assumptions of fitting unfrozen water content curve were discussed and revised, and then a semi-empirical characteristic curve of unfrozen water content during thawing is presented. The characteristic of silt, clay and silty-clay during phase transition are researched by analyzing their test results with this method. The feature of CT images grayscale of frozen soil during thawing is explored. The result discovers that the average grayscale increase obviously as temperature of frozen soil rise and during its thawing. However, after sample thaw complete, the average grayscale is not practically changing even temperature still rising. There is a break point is obviously observed at graph of grayscale-time at the moment of phase-transition finished, which is considered as a symbol of frozen soil melting complete. A mathematical model of ground settlement which include earth pressure and thaw-settlement coefficient is built by combining stochastic media theory with one dimension settlement formulas of thaw soils (former Soviet Union). The model is applied to a lateral artificial freezing engineering of connect aisle for predicting the ground settlement. |
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