静钻根植能源桩技术及其应用

Technology and application of static drilling rooted geothermal energy pile

能源桩作为一种浅层地温能利用的建筑节能技术,是建筑运行阶段减少碳排放的主要途径之一.结合静钻根植桩的特点,提出静钻根植能源桩技术及施工工艺.结合实际工程,开展静钻根植能源桩的短期工况和长期工况热力试验,分析桩身温度变化、性能系数、桩身轴向附加应力和桩侧附加摩阻力等变化规律.试验结果表明,桩身温度随时间逐渐升高,而性能系数随时间的推移逐渐降低,并最终稳定于一恒值.桩身轴向附加应力和桩侧附加摩阻力的发挥性状受桩顶、桩端约束条件的制约.短期工况试验中,桩身轴向附加应力呈中间大两头小的分布形式,桩侧附加摩阻力分布存在一个零点;长期工况下,桩身轴向附加应力呈现两端大中间小的分布形式,桩侧附加摩阻力分布规律与时间、温度和约束条件等因素有关,桩身从一个零点逐渐演变为3个.研究结果可为能源桩技术的进一步推广应用提供理论参考.

As a kind of building energy saving technology utilizing the shallow geothermal energy, energy pile is one of the ways to achieve the goal of reducing carbon emissions during building operation. Considering the shortcomings of construction technology for traditional energy pile, we propose the static drilling rooted geothermal energy pile(SDRGEP) and construction technology based on its characteristic. The short-term and long-term tests of SDREP are carried out by a test pile of a building in Ningbo. The variation properties of pile temperature, coefficient of performance(COP), thermally induced axial load and mobilized shaft resistance are analyzed. The test results show that the pile temperature gradually increases with time. COP value gradually decreases over time and then tends to be constant. Particularly, the performance of thermal axial stress and mobilized shaft resistance are determined by the constraint conditions of pile top and pile end. In the short-term test, the thermal axial stress shows the form of large in the middle and small in both ends, and there is a null point(NP). In the long-term test, the thermal axial stress at the top of the pile are larger. The mobilized shaft resistance is related to the time, temperature and constraint conditions,etc. It is varied gradually from one NP to three NPs along the pile. Therefore, the test results are related to the service state and construction technology of pile, which provides the theoretical basis for promoting the application of the SDRGEP.