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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induces a raise in the mechanical pressure in the shaft lining around the injection boreholes. The maximum of the mechanical pressure reaches on the outer side of the lining. From Fig. 6 it can be seen a redistribution of the von Mises stress in the shaft lining during the grout injection. An increase in the stress proceeds in the vertical direction. Concertation of the von Mises stress is observed on the boreholes sides. When the grout is injected through the two boreholes, the von Mises stress and the mechanical pressure near the middle borehole are almost unchanged. 4. Conclusions In the paper a fully-coupled THM model of the cement grout injection in saturated soil consisting of solid grains, pore water and pore ice is proposed. The model allows one to describe main features both the freezing and the grouting processes such as the latent heat of the water/ice phase transition, heat caused by the grout hydration, flow of fluid mixture consisting of pore water and cement grout, rheological properties of cement grout, evolution of porosity and permeability, a mechanical behavior of the soil accounting for thermal strain and strain induced by the water freezing. The governing equations of the model were implemented in Comsol Multiphysics® software. To numerically solve the equation, the finite element method was applied. The numerical simulations of the cement grouting procedure of a silty sand stratum during building of a vertical mine shaft under a protection of an ice-soil wall were conducted on the basis of the proposed model. The injection regimes through two and three boreholes were considered. To determine initial distributions of the temperature and the porosity a simulation of the ice-soil wall formation was carried out using the developed model. Results of the simulation of the cement grouting allow one to conclude the following. The grout injection through three boreholes induces a faster reduction of the pore pressure gradient than two boreholes are used. Therefore, the injection through two boreholes leads to a more intensive grout propagation. During the cement grouting the temperature of the frozen soil raises by 5 ◦ C and 8 ◦ C depending on the injection through two or three boreholes. An increase in the temperature and the pore pressure leads to raise in the volumetric strain in the ice-soil wall. In the case of using three boreholes the increment of the strain is 25% higher. The grout injection causes a redistribution of the stress-strain state of the shaft lining. The mechanical pressure increases around the boreholes and on the outer side of the lining. Concertation of the von Mises stress is observed on the boreholes sides. A raise in the stress mainly proceeds in vertical direction. Acknowledgements This research was supported by Russian Science Foundation (Grant No. 17-11-01204). References Andersland, O.B., Ladanyi, B., 2013. An introduction to frozen ground engineering. Chapman and Hall, New York. Vyalov S.S., Zaretsky, Y.K., Gorodetsky S.E., 1979. Stability of mine workings in frozen soils. Engineering Geology 13(1-4), 339-351. Li, S., Liu, R., Zhang, Q., Zhang X., 2016. Protection against water or mud inrush in tunnels by grouting: a review. Journal of Rock Mechanics and Geotechnical Engineering, 8(5), 753-766. Schmall, P.C., 2017 Grouting in Frozen Ground Conditions., in “Grouting 2017: Case Histories”. In: Bruce, D.A (Ed.). ASCE, Reston, pp. 124 132. Rahman, M., Håkansson U., Wiklund J., 2015. In-line rheological measurements of cement grouts: Effects of water/cement ratio and hydration. Tunnelling and Underground Space Technology, 45, 34-42. Yang, C., Wang, Z., 2005. Surface pre-grouting and freezing for shaft sinking in aquifer formations. Mine Water and the Environment, 24(4), 209 212. Nishimura, S., Gens, A., Olivella, S., Jardine, R. J., 2009. THM-coupled finite element analysis of frozen soil: formulation and application. Géotechnique 59(3), 159-171. Bekele, Y.W., Kyokawa, H., Kvarving, A.M., Kvamsdal, T., Nordal, S., 2017. Isogeometric analysis of THM coupled processes in ground freezing. Computers and Geotechnics 88, 129-145. Zhou M.M., Meschke G. 2013 A three-phase thermo-hydro-mechanical finite element model for freezing soils. International journal for numerical and analytical methods in geomechanics 37(18), 3173-3193. Coussy, O. 2010. Mechanics and Physics of Porous Solids. Chichester: John Wiley & Sons. Tounsi, H., Rouabhi, A., Tijani, M., Guérin, F., 2019. Thermo-hydro-mechanical modeling of artificial ground freezing: application in mining engineering. Rock Mechanics and Rock Engineering 52(10), 3889-3907. Liu, E., Lai, Y., Wong, H., Feng, J., 2018. An elastoplastic model for saturated freezing soils based on thermo-poromechanics. International Journal of Plasticity 107, 246-285.