螺旋型能量桩热-力响应原位试验研究

In-situ test study on thermal-mechanical response of spiral energy pile

针对单螺旋型、并联双螺旋型2种埋管形式能量桩在温度-荷载联合作用下开展现场原位试验,分析2种埋管形式能量桩的换热效率、桩体应变、桩体轴力、侧摩阻力等热力学变化规律。结果表明:并联双螺旋型能量桩升温时温度分布较单螺旋型能量桩更均匀,2根桩的换热功率分别稳定在9.44 kW和9.70 kW,桩体平均每延米瞬态热交换值分别为726.2 W/m和746.2 W/m;桩体最大和最小应变分别位于桩体中上部和桩端位置;升温过程中,桩侧摩阻力分布呈上负下正,中性点均位于桩体中上部;2根桩由升温产生的附加压应力分别达到7.29 kPa和6.33 kPa,由降温产生的附加拉应力分别达到-4.06 kPa和-4.75 kPa,单螺旋型能量桩由温度引起的下拉荷载比并联双螺旋型能量桩增加了885 kN,在实际工程中应给予重点关注。

The thermal-mechanical changes of heat transfer efficiency,pile strain,pile axial force and pile side friction resistance of the two types of buried energy piles were analyzed by in-situ tests under the combined temperature-load effect of single spiral and parallel double spiral.The results show that the temperature distribution of the parallel double spiral energy pile is more uniform than that of the single spiral type,and the heat transfer power of the two piles is stabilized at 9.44 kW and 9.70 kW.The average transient heat exchange values per linear meter of the piles are about 726.2 W/m and 746.2 W/m.The maximum and minimum strains of the pile are located at the middle and upper part of the pile and the end of the pile.During the warming process,the pile side friction resistance distribution is negative at the top and positive at the bottom,and the neutral point is located at the middle and upper part of the pile.The additional compressive stresses generated by the warming reach 7.29 kPa and 6.33 kPa,and the additional tensile stresses generated by the cooling reach-4.06 kPa and-4.75 kPa.The temperature-induced downward load of the single spiral energy pile increases by 885 kN compared with that of the parallel double spiral type,which should be paid attention to in the actual project.