PSI - Issue 28

M. Zhelnin et al. / Procedia Structural Integrity 28 (2020) 693–701 Author name / Structural Integrity Procedia 00 (2019) 000–000

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ground freezing (AGF) is an effective technology providing groundwater control and enhancing soil stability (Andersland and Ladanyi (2013)). An application of the technology proposes a formation of a continuous ice-soil wall around the mine shaft. During a time period of the excavation works, the ice-soil wall serves a temporary excavation support, which restricts an effect of the rock pressure on shaft sides and prevents groundwater inrush into the excavation. The mine shaft sinking under the protection of the ice-soil wall is accompanied by installing of a shaft lining consisting of a concrete shell and a cast tubbing (Vyalov et al. (1989)). The shaft lining supports the shaft sides after finishing of the artificial freezing process and thawing of the ice-soil wall. To reduce an influence of the rock pressure on the shaft lining and eliminate groundwater leakage, waterproofing and reinforcement of the soil adjacent to the shaft lining is carried out. One of the widely used method in geotechnical engineering is cement grouting (Li et al. (2016), Schmall (2017)). The objective of the method is injection of cement grout in the unfrozen soil between the shaft lining and the ice-soil wall. The injection is conducted from the shaft through a series of boreholes drilled in the shaft lining. Propagation of the cement grout in the soil leads to filling pore space by cement grains. As a result, the strength of the soil increases and its permeability reduces. For a safe grout injection in the saturated soil close by the ice-soil wall the processes of the heat transfer, mass transfer and an evolution of the stress-strain state the soil and the shaft lining should be taking into account. A rise in temperature of the soil could cause a significant decrease in the thickness of the ice-soil wall, so a breakthrough of the wall by groundwater could arise. Non-Newtonian behavior of the cement grout flow reduces the velocity and obstructs its propagation in the pore space (Rahman et al. (2015)). At the same time an excess injection pressure can disrupt an integrity of the shaft lining or induce fracture of the ice-soil wall (Yang and Wang (2005)). Thus to accurate description of the procedure of the cement grouting a thermo-hydro-mechanical (THM) model have to be developed. Recently a series of the THM models of the freezing process in water saturated soil have been proposed. The governing equations of the models are derived using the principles of the theory of porous media. Nishimura et al. (2009) have proposed a fully coupled model of freezing and thawing soil using a unified effective-stress-based framework. To describe the mechanical behavior of the soil the Barcelona-Basic Model is used. The model has been verified by a series of field tests related to an influence of frost heave of freezing soil on buried gas pipelines. Bekele et al. (2017) have presented a numerical model for freezing process in soil considering both additional strain due to phase change of water into ice and an influence of the ice pore pressure on the stress. To solve the system of equations numerically the isogeometric analysis is applied. Zhou and Meschke (2013) have derived governing equations of a fully coupled model for a soil freezing within the framework of the thermo-poro-mechanics theory by Coussy (2010). A state equation to describe an influence of the pore pressure, volumetric strain and thermal strain on the porosity during freezing is incorporated in the model. It has been demonstrated that the model captures the main aspects of behavior of freezing soil. Tounsi et al. (2019) have applied the Coussy theory to develop a THM model for a large scale simulation of AGF and excavation works in an underground mine. Results of the performed numerical simulations show good agreement to field measurements of temperature and frost heave displacements. In Lie E. et al. (2018) have established a model considering elastoplastic deformation of soil during freezing process on the basis of thermodynamic principles. The model has been verified on results of cryogenic triaxial compression test of frozen soil. Cement grout injection in water saturated soil is studied in Chupin et al. (2004, 2009), Saada et al. (2005), Maghous et al. (2007), Saiyouri et al. (2008). In Chupin et al. (2004) the grout and the saturated water are assumed to be miscible. The Darcy law is adopted to calculate the velocity of the fluid mixture. In the mass conservation equation for the grout the dispersion and diffusion phenomena of the grout are taken into account. In Chupin et al. (2009) the model has been extended to include process of the cement particle filtration and reduction of the permeability of the soil. To validate the model a large-scale injection tests were performed. It has been concluded that the filtration is not a dominant phenomenon during the grouting. In Saada et al. (2005), Maghous et al. (2007) the saturated soil upon the grouting is supposed to be a three-phase porous medium consisting of the water and cement particles and the skeleton one. A phenomenological law is used to express relationship between the permeability and the porosity. In Saada et al. (2005) the model has been applied to simulate laboratory injection tests of a sand column. In Saiyouri et al. (2008) has proposed a model considering a mechanical behavior of the soil during the grouting based on the effective stress principle. Numerical predictions have been compared to experimental results of laboratory injection tests. In Zou et al. (2018) have been developed a two-phase model of cement grout flow in rock fractures with focus on a non-