PSI - Issue 28

A. Prokhorov et al. / Procedia Structural Integrity 28 (2020) 1579–1589 Author name / Structural Integrity Procedia 00 (2019) 000–000

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2.1. All-round freezing The experiment of the first type was performed for water saturated sandy soil which was contained in a plastic cylindrical form. The radius of the form was 2.65 cm and a height was 8.4 cm. The soil specimen was equipped with thermocouple and FBG sensors (fig.1). The lines of deformation FBG sensors were located along the sample section at a distance of 5.4 cm and 2.4 cm from the upper end, passing diametrically through the central line. The sensors on the lines were half the radius from the center. The temperature FBG sensors were located on the axial line of Specimen. It is important to isolate the sensor from the mechanical deformation for measurement of temperature. In this reason, optical fiber was placed into glass tube.

Figure 1. Strain FBG (green), temperature FBG (red) and thermocouple location on axial cross section.

The thermocouples ТС1 and ТС4 were located at the lower and upper ends, the thermocouple ТС2 – on the the lateral side, and the thermocouple ТС3 – in the center of the specimen. After assembling, specimen was placed in fridge with constant temperature –20 ⁰С. 2.2. One-side freezing In the experiments of the second type the specimen was placed into a thermally insulated chamber with a cooling module through that refrigerant circulates. Temperature of refrigerant is –18 ⁰С. The specimen of water saturated sand of cylindrical shape leaned against a module side. In this case the front of phase transition propagated in the axial direction (fig. 2).

Figure 2. External view of specimen