A system development for monitoring kinetic parameters of a phase transition in a fluid-saturated soil based on fiber optic sensors

The use of fiber-optic sensors (FBG) is a promising direction of developing various science and technology fields. Bragg grating has a number of advantages over standard sensors of deformation, stress, temperature, angles of inclination. In the mining industry, FBG are typically used to monitor temperatures during the construction of an ice barrier, to analyze the occurrence of bends in the sinking of mine shafts or when driving piles. As it is known, the process of thawing and freezing of porous media is accompanied by the effects of mass and heat transfer, the formation of cryogenic flows, changes in the stress-strain state of a medium. Therefore, it is important to develop a laboratory fiber-optic monitoring system to record the temperature and deformation characteristics of the phase transition in a porous medium. In this paper we develop a system analyzing the stress-strain state of porous soils saturated with moisture in the process of occurrence and movement of the phase transition between water and ice. For the formation of a sample with the fiber-optic system placed therein, we used a designed plastic form is used which had been 3D printed. For the analysis of the kinetic parameters of the phase transition and the stress-strain state of the soil, the optical-fiber temperature and strain sensors are used. The paper deals with the compensation methods of temperature deformation on the sensors of mechanical deformation of the rock and the deformation effect on the temperature sensors. Methods of creating a system with a linearly advancing phase transition for the analysis of the kinetic features of the water-ice/ice-water system are considered. The features of the phase transition in a porous water-saturated medium are investigated.