Experimental study on compressibility of frozen saturated ISO standard sand

The compressibility of frozen soil must be taken into consideration when the deformation of highway and high-speed railway is strictly controlled in permafrost regions. The frozen saturated ISO standard sand is taken as the study object, and step load tests under different temperatures are carried out using a self-developed confined compression apparatus for frozen soils. The tests are conducted at the loads of 1, 2, 3, 5, 10 MPa and under temperatures of -0.5, -1.0, -2.0, -3.0, -5.0℃. The coefficient of compressibility and the compressibility index are obtained according to the e-σ_z and e-lgσ_z curves for both unfrozen and frozen samples at different temperatures. The experimental results of the complete temperature series from room temperature to negative temperature are then obtained. The correlation parameters are obtained according to the former modulus formulas, and the relationship between the parameters and the temperatures in the formulas is established. The test results indicate that the compression curve of frozen saturated ISO standard sand is similar to that of the samples under room temperature. For the warm frozen samples, the compressibility is considerable. The compressibility of frozen soil is closely related to temperature, i.e., the coefficient of compressibility increases with the increase of temperature in the form of exponential function. A certain quantitative relationship can be established between the parameters and the temperatures in the modulus formulas.