Abstract
Based on the vertical straight artificial freezing engineering in Northern Shaanxi, a three-dimensional (3D) physical simulation test system was developed, consisting of six parts, which are simulation box, shaft model, loading system, freezing system, external environment simulation system, and data acquisition system. The physical model and actual test results show that the 3D physical simulation test system is reasonable and reliable. The test model results show that the distance from the freezing pipe significantly affects the freezing wall temperature. For the case of four adjacent, two adjacent tangential freezing, and two adjacent axial freezing pipes, the cooling rates were 1.37, 2.79, and 1.96°C/h, respectively. The field measurement showed that the proximity to the freezing pipe increases the cooling rates. The cooling rates of points 1k#, 2k#, and 3k# were 25.61, 25.32, and 25.35 mm/d, respectively. The increment rates of vertical and horizontal freezing pressures with temperature were 8.78 and 2.97 kPa/°C, respectively. Furthermore, the freezing pressure time fitting formula was given. The calculated results of temperature and freezing pressure are consistent with the measured results, indicating the reasonability and reliability of the 3D physical simulation test scheme of the artificial freezing-inclined shaft in this work.
Highlights
Vertical straight-line artificial frozen walls are often used to excavate shafts in areas with large water content, shallow coal seam, and soft soil [1]
Wang and Wei [5] considered the phase change of water in the soil layer and the variation of the freezing temperature with time. e formation of the frozen wall and its temperature field characteristics under oblique conditions were analyzed in detail, using large-scale finite element (FE) software
When the hydration heat of concrete dissipates, the frozen wall begins to refreeze on the 6th day, and the freezing pressure increases. e freezing stops on the 17th day and the frozen wall begins to thaw. us, the supporting effect of the frozen wall decreases, and the surrounding water and soil pressure are mainly borne by the shaft. e sensor pressure culminates to 370.76 kPa
Summary
Vertical straight-line artificial frozen walls are often used to excavate shafts in areas with large water content, shallow coal seam, and soft soil [1]. Wang et al [22] used a self-made test device to study the laws of the temperature field and obtain information for predicting the frost heave and numerical simulation of artificially frozen soil He et al [23], through numerical simulation analysis and field monitoring data, studied the development law of the temperature field and frozen wall during freezing. Sheng and Wei [32] measured the multicircle temperature field of frozen walls and analyzed the problems of the shallow section, deep freezing, cold energy waste, and slow excavation speed of the frozen shaft in the early stage.
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