桥面融雪除冰能量桩热泵系统换热效率现场试验

基于能量桩的桥面工程主动式融雪除冰技术作为一种新型桥面融雪除冰技术，具有环保、节能等技术优势。依托江阴市征存路观风桥市政桥梁工程，开展能量桩供热桥面板的换热效率与热-力响应特性现场试验。在桩基础和桥面板中分别预埋聚乙烯管作为换热管，通过水泵驱动换热管中的流体循环，提取浅层地温能供热桥面板；沿桩身深度方向和在桥面板中布设了温度-应变传感器，用于监测试验过程中相应位置的温度和应变。试验分析冬季工况下，一根20 m的能量桩供热20 m²的桥面板时，流体、桥面板、桩的温度变化以及桥面板和能量桩的热致应力分布。研究结果表明：根据现场试验条件，环境温度为-4℃时，20 m能量桩供热20 m²桥面板可保证桥面板表面温度始终高于0℃，即平均每延米能量桩热泵系统可保障1 m²桥面板不冻结；温度的改变使得能量桩和桥面板中产生热致应力，桩身最大轴向热致应力出现在桩深10 m （50%桩长）处，约为-1.05 MPa，为混凝土抗拉强度（2.0 MPa）的52.2%，桩身最大轴向热致应力的温度响应约为0.205 MPa·℃^-1；桥面板中最大热致应力为0.77 MPa，为混凝土抗压强度（26.8 MPa）的2.9%，热致应力的温度响应为0.086 MPa·℃^-1；能量桩上部受到最大正摩阻力为21.1 kPa，下部受到最大负摩阻力为13.3 kPa；试验结束时桩顶热致位移为-0.239 mm，约0.03%桩径。

Field Tests on Heat Transfer Efficiency of Bridge Deck Snow Melting and Deicing Using Energy Pile Heat Pump System

As a new type of bridge deck snow melting and deicing technology, active deicing technology based on energy piles, has the advantages of environmental protection and energy savings. Field tests were performed on the municipal bridge, Guanfeng Bridge, Zhengcun Road, Jiangyin City, to investigate the heat transfer performance between the energy piles and bridge decks. Polyethylene pipes were embedded in the pile foundation and bridge deck as heat exchanger pipes, and the fluid in the heat exchanger pipes was driven using a water pump to extract shallow geothermal energy to heat the bridge deck. Temperature-strain sensors were installed in the bridge deck and the energy pile to monitor the temperature and strain variations in the corresponding positions during the tests. A 20 m long energy pile was used to heat a 20 m² area bridge deck in winter. The temperature variations of the fluid, bridge deck, and pile and the thermally induced stresses of the bridge deck and energy pile were analyzed. Under the test conditions, when the ambient temperature is -4℃, a 20 m energy pile heating 20 m² bridge deck can ensure that the surface temperature of the bridge deck is always higher than 0℃; that is, 1 m² bridge decks can be protected from freezing by the 1 m energy pile. During the tests, the changes in temperature yielded thermal-induced stress in the energy pile and bridge deck. The maximum axial thermal stress of the pile appears at 10 m (0.5 times the pile length); its value is approximately -1.05 MPa, which is 52.2% of the tensile strength of concrete (2.0 MPa). The temperature response of the maximum axial thermal stress of the pile is approximately 0.205 MPa·℃^-1. The maximum thermal stress in the bridge deck is 0.77 MPa, which is 2.9% of the compressive strength of concrete (26.8 MPa), and the temperature response of the thermal stress is 0.086 MPa·℃^-1. The maximum positive frictional resistance on the upper part of the pile is 21.1 kPa, and the maximum negative friction resistance on the lower part is 13.3 kPa. At the end of the tests, the thermal displacement of the pile top is -0.239 mm, approximately 0.3‰ times the pile diameter.