多年冻土区钻孔灌注桩施工过程热力特性研究  

Study on Ground Thermal Regime and Bearing Capacity of a Cast-in-place Pile in Permafrost Regions

作　　者：商允虎 牛富俊 吴旭阳 刘明浩 苗褀 袁堃[3] SHANG Yunhu;NIU Fujun;WU Xuyang;LIU Minghao;MIAO Qi;YUAN Kun(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;CCCC First Highway Consultants Co.,Ltd.,Xi’an 710075,China)

机构地区：[1]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049 [3]中交第一公路勘察设计研究院有限公司,陕西西安710075

出　　处：《铁道学报》2020年第5期127-135,共9页Journal of the China Railway Society

基　　金：第二次青藏高原综合科学考察研究(2019QZKK0905);冻土工程国家重点实验室自主研究课题(SKLFSE-ZQ-51);陕西省创新能力支撑计划(2017KJXX-26);青藏集团公司科技研究开发计划(QZ2018-G01)。

摘　　要：钻孔灌注桩水化热会暖化冻土引起桩基承载力下降,以桩基水化热在时间与空间上的影响效应为研究目的,结合青藏公路G214沿线查拉坪旱桥桩基观测数据,分析水化热对地温场的扰动范围以及桩周土回冻时间,给出灌注桩18 d内的养护温度。结果表明:水化热对距桩1.95 m以外地温影响微弱;144 d后桩侧温度降至0℃以下,229 d后桩侧温度低于-0.5℃;2 a后桩侧基本回冻至天然地温,此时承载力已达到设计要求。桩基混凝土养护温度前5 d在10℃以上,5~12 d在5℃以上,12~15 d为2℃以上,15~18 d仍高于0℃。通过数值仿真给出混凝土入模温度及桩基施工时间对桩周温度场的影响,模拟结果显示,该区域的灌注桩施工可以在相应规范规定范围内提高混凝土入模温度;灌注桩施工可以在冷季进行,但要做好5 m以上深度桩基混凝土的温控措施。Based on the temperature field observation of permafrost around a pile foundation of Chalaping Bridge, this paper analyzed the temperature-disturbing range of hydration heat to the ground temperature field and the freezing-back time. The results show that the hydration heat of the cast-in-place pile had little influence on the ground temperature 1.95 m far from the pile. Vertically, the ground temperatures at all depths dropped below 0℃ after 144 days, and below-0.5℃ after 229 days. The cast-in-place pile foundation experienced two years of cooling to freeze back to natural state, when the bearing capacity of the pile had reached the design goal. The curing temperature was above 10 ℃ during the first 5 days, above 5 ℃ during 5-12 days, above 2 ℃ during 12-15 days and above 0 ℃ during 15-18 days. The influences of mold temperature and construction time on thermal regime were simulated. The computation results indicate that the mold temperature can be raised within the prescribed scope, and cast-in-place pile can be constructed during cold season, but temperature control measures for pile foundation concrete with a depth of more than 5 m should be taken. Experiences learned from the cast-in-place pile foundation of Chalaping Bridge will be of value for future pile foundation construction in permafrost regions.

关 键 词：多年冻土区 桥梁 桩基 温度场 

分 类 号：TU473[建筑科学—结构工程]