冬季工况多次温度循环下微型钢管桩群桩热力响应特性现场试验

能量桩技术具有支撑上部结构和浅层地热能换热器双重作用;作为一种节能减排新技术,近年来获得了一定的发展。依托微型钢管桩加固既有基础托换工程,开展冬季工况多次温度循环下微型钢管桩群桩的热力响应现场试验;实测不同间歇时长情况下桩身温度与应力等变化规律,探讨不同运行模式下的桩基换热性能系数（C_OP,coefficient of performance）。试验结果表明：文中试验条件下,桩身附加温度应力随循环次数增加而增大,且随间歇时间的延长而减小;桩基C_OP随循环次数增加而减小,且随间歇时间的延长而增大;附加拉应力未超过设计控制范围、不会导致桩体破坏。

Field tests on thermal response characteristics of micro steel pile group under multiple temperature cycles in winter conditions

The energy pile technology has dual functions of supporting superstructure and acting as shallow geothermal heat exchanger. As an energy-saving and emission-reduction technology, it has obtained certain development in recent years. Relying on the micro steel piles to reinforce the existing foundation underpinning project, the field tests on thermal response of the micro steel group piles under multiple temperature cycles are carried out. The variation of pile temperature and pile stress under different intermittent time is measured. The coefficients of performance (C_OP) of piles are discussed and analyzed. It is shown that the additional thermal stress of piles increases with the increasing cycling times, and the increase ratio decreases with the interval time; the C_OP of piles decreases with the increasing cycling times, and the decrease ratio decreases with the interval time. The values of the additional tensile stress does not exceed the design control range, which will not cause the damage of the pile.