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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Fig. 4. Distributions of the volumetric strain ε vol across a horizontal section of the soil stratum possesses through the injection boreholes at the start of the grout injection (a), after 24 hours of the grout injection through two boreholes (b) and three boreholes (c). The white line corresponds to the position of the phase transition boundary. boreholes intensive heat transfer by convection is observed. In the region the temperature raises up to 20 ◦ C. In far away from the boreholes the heat transfer is mainly realized by the heat conduction. The position of the phase transition front almost does not change. However, the temperature of the frozen soil raises by 5 ◦ C and 8 ◦ C during the injection through two and three boreholes. Fig. 4 shows distributions of the volumetric strain. Before the grouting the strain is negative due to of action of the overburden pressure. The strain in the unfrozen zone is higher, since the frozen soil is stiffer than the unfrozen one. A raise in the pore pressure and the temperature induced by the grout injection leads to an increase in the strain. The pore pressure in neighboring with the injection boreholes areas compensates the effect of the overburden pressure and a volumetric expansion of the soil occurs. Besides the volumetric strain increases near the phase transition boundary because of an affect of pore pressure induced by the water and thermal strain. In the case of the injection through three boreholes the increment of the strain in the frozen zone near the phase transition boundary is 25% higher. A mechanical response of the shaft lining on the grout injection is presented in Fig. 5, 6. The grout injection

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Fig. 5. Distributions of the mechanical pressure (Pa) in the shaft lining at the start of the grout injection (a), after 24 hours of the grout injection through two boreholes (b) and three boreholes (c). The black surface corresponds to distribution of the grout concentration.

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Fig. 6. Distributions of the mechanical pressure (Pa) in the shaft lining at the start of the grout injection (a), after 24 hours of the grout injection through two boreholes (b) and three boreholes (c). The black surface corresponds to distribution of the grout concentration