PSI - Issue 32
A. Kostina et al. / Procedia Structural Integrity 32 (2021) 101–108 A. Kostina/ Structural Integrity Procedia 00 (2021) 000 – 000
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considered by application of the external load obtained on the first step to the domain. Calculations were carried out for two initial thicknesses of the frozen wall. In the first case the soil was frozen up to the contour of the future shaft, in the second case initial thickness corresponded to project documentation.
Fig. 1. Geometry of the domain and boundary conditions.
Fig. 2-3 show distribution of von Mises stress in silt and sand stratums for 4 th day after shutdown of the freezing wells. The obtained results have similar qualitative character. Maximum value of the stress is observed near the freezing well in both soils. Values of stress near the unfixed section of frozen wall in sand are higher than in silt and equal to 2.3MPa while in silt this value is 1.2 MPa. Figs. 4-5 present distribution of xx component in silt and sand stratums obtained for 4 th day of thawing. Strains located to the right from the freezing well are compressive while strains located to the left are tensile in both soils because the unfixed boundary of the wall can move to the center of the future shaft but the freezing well prevents this displacement for the part of the soil located to the right from it. Maximum value of the strain near the unfixed section in silt has been obtained for the first thickness and is equal to 0.9%. For the second thickness this value is 0.32%. In sand maximum value of xx near the unfixed section is lower than in silt and is equal to 0.12% for the first thickness and 0.13% for the second thickness. Fig. 6 displays distribution of horizontal displacements in silt for 4 th and 200 th day of thawing. The obtained results show that in all cases displacement of the unfixed part of the wall does not exceed 10 cm even for shutdown of freezing wells for period of time equal to 200 days. Maximum value at 200 th day is attained for the initial thickness of the wall corresponding to project documentation. This can be explained by substantial thawing of soil and its intensive displacement into the stope.
(a)
(b)
Fig. 2. Distribution of von Mises stress (Pa) in silt at 4 th day after shutdown of freezing wells (a) soil was frozen up to the contour of the shaft; (b) soil was frozen up to the project thickness.
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