Energy pile test at Lambeth College, London: geotechnical and thermodynamic aspects of pile response to heat cycles
Energy pile test at Lambeth College, London: geotechnical and thermodynamic aspects of pile response to heat cycles
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DOI：
10.1680/geot.2009.59.3.237
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发表时间：
2009-01-01
期刊：
影响因子：
5.8
通讯作者：
Payne, P.
中科院分区：
文献类型：
--
作者：
Bourne-Webb, P. J.;Amatya, B.;Payne, P.
关于加热和冷却过程对包含地源热泵系统管道回路的桩基（所谓的能源桩）的岩土性能的影响，现有的信息非常有限。桩荷载试验，包括温度循环，而在一个延长的时间保持加载进行调查的行为，安装在伦敦粘土的能量桩。测试进行了大约七个星期的时间，与传统的负载测试进行了延长负载测试与热循环的任何一方。使用光纤传感器系统，和其他更传统的仪器，温度和应变分布进行了观察，在测试桩，相邻的钻孔，两个锚桩，和散热桩。还记录了桩头处的载荷和运动、环境空气温度和加热系统内流体的输入/输出温度的详细信息。试验期间观察到的热力学行为支持以下假设：桩体充当无限长的散热器/热源，且伦敦粘土所用的传导率值合理。已从试验响应中推断出桩身中的动员力和桩/土界面处的动员阻力，并使用简化机制描述了影响。当桩被加热时，会产生除静荷载外的混凝土应力，桩端约束条件会影响效果;混凝土应力可能会超过设计规范规定的限值。在这种情况下，在热循环过程中，桩的极限轴向阻力和桩/土界面处的剪切应力之间存在较大的裕度，因此，认为桩的岩土承载力不太可能受到显著影响。
Very limited information is available regarding the impact of heating and cooling processes on the geotechnical performance of piled foundations incorporating pipe loops for ground-source heat-pump systems (so-called energy piles). A pile-loading test that incorporated temperature cycles while under an extended period of maintained loading was undertaken to investigate the behaviour of an energy pile installed in London Clay. Testing was carried out over a period of about seven weeks, with conventional loading tests carried out either side of an extended loading test with thermal cycles. Using an optical fibre sensor system, and other more conventional instrumentation, temperature and strain profiles were observed in the test pile, an adjacent bore-hole, two of the anchor piles, and the heat sink pile. Details of load and movement at the pile head, of ambient air temperature and of the input/output temperature of fluid within the heating system were also recorded. Thermodynamic behaviour observed during the test supports the assumption that the pile acts as an infinitely long heat sink/source, and that the conductivity values used for the London Clay were reasonable. Forces mobilised in the pile shaft and the resistance mobilised at the pile/soil interface have been inferred from the test response, and the effects have been described using a simplified mechanism. Concrete stresses additional to those due to static loading are generated when the pile is heated, and the pile end-restraint conditions influence the effect; concrete stresses could potentially exceed the limiting values imposed by design codes. In this case there was a large margin between the pile ultimate shaft resistance and the shear stresses mobilised at the pile/soil interface during thermal cycling, and as a consequence, it is considered unlikely that the geotechnical capacity of the pile was affected significantly.