Abstract:
The natural thawing condition of the frozen well is the basis for selecting a reasonable time for inter-wall grouting. Taking the west wind well of Yuandian No.2 Mine in Linhuan Mining area of Huaibei Coal field as the engineering background, the spatio-temporal evolution of the temperature field of the frozen wall during the thawing process is studied using field measurement and numerical calculation methods, and a reasonable time for inter-wall grouting is given. The results show that: in the natural thawing process, the warming process of the freezing temperature field is divided into low temperature rapid warming stage, phase transition slow warming stage and positive temperature rapid warming stage. In the range of 4−10 m radial distance on the freezing interface of the freezing wall, the average temperature rise rate of −135 m fine sand layer during the negative temperature rise stage is 0.075 ℃/d. The heating rate of −150 m clay layer is 0.063 ℃/d. The heating rate of −215 m clay layer is 0.074 ℃/d. The temperature rise rate of −241 m calcareous clay layer is 0.067 ℃/d. The average temperature of the effective freezing wall rises faster in the negative temperature and temperature rise stage, while the average temperature of the freezing wall rises slowly in the phase transition and positive temperature and temperature rise stage. The freeze-thaw ratio of the fine sand formation is 1.32−1.48. The ratio of thawing to freezing in clay strata is 1.49−1.73. During the thawing of the frozen wall, under the synergistic action of frost heave force and soil-water pressure, the radial and reverse elastic displacement occurs between the inner and outer layers of the frozen well, and the gap between the double walls increases, thus providing a channel for the diffusion of grouting slurry between the walls. Therefore, when the frozen wall is completely thawed and the gap between the walls is formed under the action of pressure water, the grouting effect is better before the inner wall is discharged.