Experimental research on unfrozen water content of frozen soils by calorimetry

Unfrozen water content is not only an important evaluation index of water migration in frozen soils,but also a common parameter in thermotechnical calculation. Six types of soil samples (totally 76) which are collected from the permafrost of Da Hingang Mountains on the section of Daqing-Mohe in the China-Russia oil pipeline project are measured by calorimetry at such temperatures as about -0.5℃,-2℃,-5℃ and -10℃. The principle and equipment of calorimetry are introduced firstly. According to a large number of test data,The analyses of the influencing factors and their variations of unfrozen water content,which include temperature,soil type and initial moisture content are made. The representative values of unfrozen water content at four given temperature in the six types of soils are obtained through statistical analysis. The coefficients of unfrozen water contents at different given temperatures are obtained by normalizing the unfrozen water content and plastic limit water content. The empirical formulas for unfrozen water contents in clay,silty clay,silt and peat soil are given through fitting unfrozen water content,plastic limit and temperature with power function. Finally,making comprehensive analysis of temperature,soil condition and initial water content,we get binary linear regression equation on unfrozen water content,initial water content and plastic limit water content,so as to provide reference for actual engineering.