埋深条件下含承台能量桩基础换热效率及热力响应现场试验  

Field Test on Heat Transfer Efficiency and Thermal Mechanical Response of Energy Pile Foundation with Cap Under Embedded Depth

作　　者：陈玉 孔纲强 孟永东[1] 王乐华[1] 刘红程[1] CHEN Yu;KONG Gang-qiang;MENG Yong-dong;WANG Le-hua;LIU Hong-cheng(Key Laboratory of Geological Hazards on Three Gorges Reservoir Area of Ministry of Education,China Three Gorges University,Yichang 443002,Hubei,China;Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210098,Jiangsu,China)

机构地区：[1]三峡大学三峡库区地质灾害教育部重点实验室,湖北宜昌443002 [2]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098

出　　处：《建筑科学与工程学报》2021年第5期91-98,共8页Journal of Architecture and Civil Engineering

基　　金：国家自然科学基金项目(51778212)。

摘　　要：依托埋深条件下低承台2×2群桩基础,在钻孔灌注桩钢筋笼上绑扎换热管形成能量桩,布置振弦式应变计/温度计以测试桩身温度及热致应变。开展恒定水温(35℃)输入情况下,单根能量桩运行对邻近桩基、承台的热力响应特性试验;实测进/出口水温随时间变化、桩身热致应变等变化规律,分析埋深条件对单根能量桩的换热效率及其对承台和邻近桩体热力响应特性的影响规律,并与无埋深条件下的换热效率、热力响应特性展开对比分析。结果表明:试验条件下,3 m埋深条件下的换热效率为2.65 kW,较无埋深条件下提升了约68%,体现出上覆回填土存在一定的持热能力;有/无埋深条件下,桩身热致应力最大值分别出现在桩身中部及桩顶,分别为1.66 MPa和2.14 MPa;随加热过程的进行,桩端阻力呈现先增大后逐渐下降至稳定值的变化趋势,在加热24 h后达到最大值约20 kPa,与进/出口温度差变化趋势一致;有/无埋深条件下承台在加热工况均出现了细微的差异变形,在设计承台能量桩结构时应给予一定的考虑;有/无埋深条件下承台最大热致应力值分别为0.65 MPa和2.34 MPa,对应的最大温度升幅分别为3.6℃和11.0℃。Based on the low-cap 2×2 pile foundation under embedded depth condition,heat exchange tubes were tied on the bored pile reinforcement cage to form energy piles,and vibrating wire strain gauges/thermometers were arranged to test the temperature and thermal strain of the pile body.The thermal mechanical response characteristic test of a single energy pile operation to the adjacent pile foundation and cap under the constant input water temperature(35℃)was carried out;the inlet/outlet water temperature changing with time and the thermal strain of the pile body were measured.The heat transfer efficiency of a single energy pile and its thermal mechanical response characteristics of the cap and adjacent piles were compared and analyzed under the condition of with/without embedded depth.The results show that the heat transfer efficiency under the 3 m depth is 2.65 kW,which is about 68%higher than that of no embedded depth in this field test condition,reflecting the existence of a certain heat retention capacity of the overlying backfill.Under the condition of with/without embedded depth,the maximum thermal stress of the pile body appears in the middle of the pile body and the pile top respectively,which are 1.66 MPa and 2.14 MPa.During the heating process,the pile tip resistance increases first and then gradually decreases to a stable value.After heating for 24 h,it reaches a maximum value of about 20 kPa,which is consistent with the change trend of the inlet/outlet temperature difference.Under the condition of with/without embedded depth,the cap shows slightly different deformations in the heating conditions,and certain consideration should be given to the design of the energy pile structure with the cap.The maximum thermally induced stress values of the cap with/without embedded depth are 0.65 MPa and 2.34 MPa respectively,and the corresponding maximum temperature rise is 3.6℃and 11.0℃.

关 键 词：能量桩 基础埋深 换热效率 热力响应 现场试验 

分 类 号：TU443[建筑科学—岩土工程]