Numerical analysis of three-dimensional freezing temperature field in deep alluvial layer based on differential freezing technique
In order to investigate the distribution and development of temperature field in the artificial ground freezing (AGF) multi-loop pipe frozen wall,taking the Dongfeng Shaft of Qingdong Coal Mine in Huaibei city as the engineering background,a three-dimensional numerical model of the frozen temperature field was estab-lished using field measurement data and COMSOL Multiphysics software. The spatiotemporal evolution of the frozen temperature field in the soil layer of the vertical wellbore under different freezing techniques were ana-lyzed. The research results showed that in the comparative analysis,the three-loop pipe had a faster freezing ex-pansion speed compared to the two-loop pipe. Under the same freezing time,the average temperature of the fro-zen wall was 0.73 ℃ to 3.32 ℃ lower,and the effective thickness increased by 0.38 m. In the sandy soil layer,the average temperature of the frozen wall was 0.94 ℃ to 1.5 ℃ lower than that in the clay soil layer under the same freezing time,and the effective thickness increased by 0.21 m. Within the calculation scope of the frozen wellbore,the radial temperature field showed a "Saddle-shaped" distribution,with lower temperatures between the loop pipes and higher temperatures on both sides of the loop pipes. In the depth direction of the soil,the tem-perature gradient of different soil layers with different soil properties was more pronounced. Specifically,the three-loop pipe and the fine sand layer had lower temperatures. Around 30 d,the temperature decrease rate in the Layer Ⅱ soil (sand layer with three-loop pipe) reached its maximum,about 1.12 ℃·d-1,indicating that it had entered the stage of frozen wall intersection and expansion,while other soil layers were still in the stage of temperature decrease. The arrangement of the "Long and Short Leg" frozen pipes can not only increase the exca-vation time of the well and shorten the construction period,but also prevent excessive freeze-thaw of the deep frozen soil,reduce the difficulty of excavation,and save construction costs. By using differential freezing meth-od,the freezing was initiated for 30 d,and after the temperature of the seepage brine dropped to-30 ℃,the tem-perature of the circulation refrigerated brine was maintained,ensuring the complete success of the freezing proj-ect. This study can provide reference for similar mine freezing construction.
artificial ground freezingdifferential freezing techniquethree-dimensional freezing temperature fieldtemporal and spatial evolutionnumerical calculation
万方数据
维普
