夏季制冷循环下PCC能量桩负摩阻力特性研究

Negative Skin Friction Behavior of PCC Energy Pile under Heating Cycle

基于传统PCC(Large Diameter Pipe Pile by Cast-in-place Concrete)桩研发的新型PCC能量桩技术,具有埋管方便、热传导效率高等技术优点。目前针对循环温度下该新型能量桩负摩阻力特性的研究仍相对较少。基于模型试验方法,开展循环温度影响下PCC能量桩的静载荷试验,测得循环温度作用下PCC能量桩的荷载一位移关系,以及桩、土温度等变化规律曲线;进而,通过针对桩侧摩阻力的计算与分析,对实际运行过程中PCC能量桩的承载特性与负摩阻力进行了初步讨论。结果表明,风干砂土中PCC能量桩的竖向承载力随着桩体温度的升高而略有增加;PCC能量桩桩侧摩阻力变化规律与常规能量桩规律一致;制冷循环结束后,能量桩顶部出现负摩阻力区,工程设计人员需要格外关注。

Based on traditional PCC pile, one of new type energy pile was developed. This new PCC energy pile has many advantages, such as, conveniently buried and high thermal conduction efficiency. However, the researches on negative skin friction of this new type energy pile influ- enced by temperature are relatively little. Based on model test method, the properties of PCC en- ergy pile was carried out. Load-displacement curves under different temperatures and the temper- ature variation of pile and soil were measured, and the friction of pile shaft was also calculated. The bearing capacity and negative skin friction of PCC energy pile influenced by pile temperatures were discussed and analyzed. The results show that the bearing capacity of PCC energy pile is im- proved with the increment of pile temperature, which is similar with traditional solid energy pile. At the end of cooling, the direction of mobilized shaft resistance near top part of pile conversed and negative skin friction appeared.