能源群桩与单桩热-力学响应特性对比分析

针对热-力耦合作用下能源群桩和单桩连续72 h放热工况以及间歇运行工况的传热和力学响应过程进行了三维动态数值模拟,对比分析了二者连续运行工况下的桩身温度、桩身应力、附加温度荷载、桩身截面位移、桩侧阻力以及间歇运行工况下的出口水温、桩心温度和桩顶位移。结果表明:虽埋管出口水温相近,但群桩与单桩的桩身温度差异较大,进而会引起桩身截面位移以及桩身应力等一系列能源桩力学响应不同;对能源桩施加结构荷载和温度荷载后,单桩的桩身应力大于群桩中各桩的桩身应力,并在桩身中下部达到峰值,附加温度应力在桩身主体段几乎相等;桩基出现整体沉降,但随着加热的进行出现了桩顶向上移动、桩底向下伸长的趋势;侧摩阻力沿桩深方向不断增大,在桩底处达到最大值;间歇运行工况下,能源桩出口水温、桩心温度以及桩顶位移出现明显的波动,呈现出累加效应。

Comparative Analyses on Thermo-Mechanical Characteristics of Energy Pile Group and Single Energy Pile

Three dimensional dynamic numerical simulations were conducted on thermal and mechanical responses of energy pile group and single energy pile to 72-hour continuous and intermittent heat rejection processes. The temperature of piles body, piles stress, additional temperature load, piles section displacement and lateral resistance of the piles were analyzed. Results show that the outlet water temperatures of the buried pipes are similar, but temperature differences of pile body between the pile group and the single pile are obvious, leading to a series of differences of mechanical responses between two pile types, such as pile body displacement and additional temperature stresses, etc. With mechanical force loaded on the top, the single pile exhibits greater stress than each pile in the pile group and the stress reaches the maximum in the lower part of the pile body. The additional temperature load is almost equal in the main part of the pile but varies dramatically near the pile tops and bottoms. With structure load exerted on the top, the settlements of the whole pile occur. But as time proceeds, the tops of the piles move upward and the bottoms move downward. The lateral resistance of the piles increases along the depth direction and reaches the maximum at the pile bottom. The outlet water temperature, pile temperature and displacement of energy piles fluctuate obviously under intermittent operational condition, and accumulative effect appears.