多年冻土区静钻根植桩回冻过程温度场研究

Study on Temperature Field of Refreezing Process of Static Drill Rooted Pile in Permafrost Regions

基于传热学理论,给出桩土温度场偏微分方程及边界条件,结合低温稳定多年冻土区地质背景,通过有限元数值分析求解,分析静钻根植桩回冻过程桩土温度场随时间的分布变化规律,讨论水泥掺入量及水泥土的水泥浆体初始拌入温度对回冻过程的影响.结果表明,地表下2m以内桩土温度受大气温度影响较明显,水化热对1.5倍桩径以外及桩底1~2m以下范围桩土温度影响甚微,17 d后桩侧温度回冻至0℃,27d桩侧温度降至-0.5℃以下;水泥浆体初始拌入温度每升高5℃,回冻时间增长5~6 d;水泥掺入量每减少10%,回冻时间缩短1~2 d.静钻根植桩的温度场同样受水化热影响,但回冻时间较短;通过调整水泥浆体配合比和降低水泥浆体初始拌入温度可兼顾水泥土强度和回冻时间要求,达到提高承载力、缩短施工工期的目的.

Based on the theory of heat transfer,a partial differential equation and boundary condi-tions for the temperature field of pile-soil were listed,and combined with the geological background of low temperature stable permafrost area,finite element numerical analysis was used to seek the solution.The distribution and variation of the temperature field of pile soil during the process of static drilling rooted pile refreezing were analyzed,and the influence of cement dosage and initial mixing temperature of cement slurry on the refreezing process was discussed.The results show that the temperature of pile and soil within 2 m below the surface was significantly affected by the atmospheric temperature,the hydration heat had little effect on the temperature beyond 1.5 times the pile diameter and within 1~2 m below the pile bottom,and after 17 d,the temperature of pile side was frozen to 0℃,and after 27 d,the temperature of pile side dropped to below-0.5℃.When the initial mixing temperature of cement paste increased by 5℃,the refreezing time increased by 5~6 d and the refreezing time was shortened 1~2 d for every 10%reduction in cement dosage.The temperature field of the static drill rooted pile was also affected by the hydration heat,but the refrozen time was shorter.By adjusting the cement slurry mix ratio and reducing the initial mixing temperature of cement paste,the requirements for ce-ment soil strength and refrozen time could be met,thereby improving the bearing capacity and shorten-ing the construction period.