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基于多年冻土区桩基混凝土的设计与施工,研究了多年冻土区大直径钻孔灌注桩的早期回冻规律,通过桩基现场试验并结合数值仿真模型分析了桩周混凝土水化热和桩周冻土回冻规律。分析结果表明:在灌注完成后25d内桩侧温度在1℃以上,在灌注完成45d后桩侧温度逐渐恢复到0℃;数值模拟结果显示在灌注完成60d后桩身温度下降至0℃,在灌注完成200d后桩周土体回冻至天然状态;入模温度每提高2℃,桩侧峰值温度提高1℃左右,而2倍桩径处峰值温度提高0.5℃左右。可见,在大直径桩基条件下桩基混凝土中可以不添加或少添加早强剂,也没有必要刻意降低拌合物入模温度;桩基的施工时间最好安排在暖季,为混凝土的养生提供较好的外部条件。
Based on the design and construction of pile-foundation concrete in permafrost regions, the early-freezing rule of large-diameter bored piles in permafrost regions was studied. Based on the pile foundation test and the numerical simulation model, Frozen soil freeze - thaw law. The results show that the temperature of the pile side is above 1 ℃ within 25 days after the completion of filling, and the temperature of pile side gradually returns to 0 ℃ 45 days after the completion of filling. The numerical simulation results show that the temperature of pile body drops to 0 ℃ after 60 days of filling, After 200 days of filling, the soil around the pile is back to the natural state. When the temperature of the mold increases by 2 ℃, the peak temperature of the pile side increases about 1 ℃, while the peak temperature at 2 times of pile diameter increases about 0.5 ℃. Can be seen in the pile foundation under large diameter pile foundation can be added without additives or less early strength agent, there is no need to deliberately reduce the mold into the mold temperature; pile construction time is best arranged in the warm season, for the concrete Health to provide better external conditions.