竖向和水平组合荷载下能量桩单桩变形特性

Deformation characteristics for single energy pile under combined loads in vertical and horizontal directions

能量桩作为一种新型能源地下结构,在承受上部建筑荷载同时,能够获取浅层地热能。目前针对水平荷载与竖向荷载共同作用下的能量桩热力学特性的研究较少,而水平荷载与竖向荷载共同作用下,桩身温度变化会引起桩体弯矩、水平和竖向位移等发生变化。基于模型试验,对桩体施加10次冷热循环,开展了竖向和水平组合荷载下能量桩的变形特性研究。结果表明,组合荷载下冷热循环会进一步增大桩身弯矩,且对桩体中部的影响更大,最大桩身弯矩增幅达到了117%;冷热循环会产生桩顶累积位移,试验桩竖向位移增加了0.201 mm,温度作用引起的水平位移增加值达到了1.46%D(D为桩体直径);同时,冷热循环会导致桩向桩前倾斜,10次冷热循环后转角达到1.88×10^(-3)rad,且会随着循环次数增加有缓慢增加趋势;加热时桩前土压力减小,而制冷时使桩前土压力增大。

Energy piles,as innovative energy underground structure,serve the dual purpose of shallow extracting geothermal energy while bearing the upper building load.There are few studies on the thermomechanical properties of energy piles under combined horizontal and vertical loads.The temperature change of pile body under combined horizontal and vertical loads will result in variations in pile bending moment,horizontal and vertical displacement,etc.This paper investigated the deformation characteristics of energy piles under combined vertical and horizontal loads through model tests with 10 heating-cooling cycles applied to the piles.The results showed that the heating-cooling cycles under combined load led to further increase in the pile bending moment,particularly affecting the middle section of the pile,with the maximum increase in pile bending moment reaching 117%.Additionally,the heating-cooling cycles caused cumulative displacement at the top of the pile.The vertical displacement of the test pile increased by 0.201 mm,and the increase in horizontal displacement due to the thermal cycles reached 1.46% D(D is the diameter of the pile).Simultaneously,the heating-cooling cycles induced a forward tilt of the pile,with the tilt angle reached 1.88×10^(−3) rad after 10 heating-cooling cycles and gradually increasing with the number of thermal cycles.Moreover,the soil pressure in front of the pile decreased during heating,while increased during cooling.