温度循环下能量群桩的热-力学特性数值分析

Numerical Analysis of Thermo-mechanical Behavior of Energy Pile Group in Clay Subjected to Cooling-heating Cycles

以黏土地基中能量群桩作为研究对象,针对能量桩-筏基础建立了简化的二维热-渗流-力(THM)耦合有限元模型,模拟分析了力学荷载与长期冷-热循环共同作用下能量群桩的热-力学特性。研究结果表明:桩头沉降、桩身轴向应力、地基土的温度和超静孔压均随温度循环呈周期性变化。桩头的沉降累积主要发生在第1个温度循环中,边桩桩头累计沉降最大,内部桩头的累积沉降较小。边桩轴向压应力的幅值远大于中心桩。在温度循环中各相邻桩间土的温度相同,筏板外地基土的温度较之桩间土要小得多。温度循环下地基土产生超静孔隙水压力。桩升温时桩间土中的超静孔压沿深度逐渐减小,而筏板外地基土的超静孔压小于桩间土。能量群桩的群桩效应减小了温度循环引起的桩身轴向应力和筏板的差异沉降。

Energy pile group in clay is taken as the study object.A simplified coupled multi-physical 2D finite element model was developed to investigate the thermo-mechanical response of a piled raft equipped with floating energy piles in clay subjected to cooling-heating cycles combined with the mechanical load.The results show that the pile head settlements,axial stresses in the piles,temperatures and the excess pore pressures in the ground change periodically with the thermal cycles.Most of the pile head settlements accumulate in the first thermal cycle.The edge pile head has the largest cumulative settlement,and the internal pile heads have smaller accumulated settlements.The amplitude of the axial compressive stress in the edge pile is much larger than that of the central pile.The temperatures in the soil between adjacent piles are the same during the thermal cycles,and the ground temperature outside the raft is much smaller than that of the surrounding soil.The thermal cycles induce the excess pore pressure in the subsoil.When the piles are heated,the excess pore pressure decreases gradually along the depth in the surrounding soil.While,the ground temperature outside the piled raft is lower than that of the soil between energy piles.The thermally induced group effect reduces the axial stress in the energy piles and the differential settlement of the energy piled raft.