Abstract: It is very important to determine the coefficient of wetting collapsibility of collapsible loess. All current methods in the building code have disadvantages in the one or other aspects in determining this parameter. This paper analyzes various methods in determining the coefficient of wetting collapsibility and presents a new approach for the determinations of both overburden pressure in the laboratory testing and coefficient itself. Both the safety factors in in the engineering projects and the approaches of the new method and an existing method of coefficient of wetting collapsibility determination were compared and the resultant values were presented. The investigation results indicated that, in the existing method, the overburden pressure applying on the test sample is unreasonable and the tested coefficient of wetting collapsibility is generally lower than that of in the site condition. Further, in the calculating the coefficient, the total deformation is based on the original height of the sample and this is not consistent with the actual site conditions. Although, a small sample rebound can be obtained, the factor of wetting should be considered from both the definition the coefficient of wetting collapsibility and the comparison of the calculation result. The deformation under the overburden pressure is far less than that of from the wetting, which indicating the soil sample is collapsible loess. In conclusion, the water infiltration is the leading factor of deformations in loess soils.

Key words: Coefficient of Wetting Collapsibility, Overburden Pressures, Laboratory and Insitu Tests, Analysis Methods