循环温度和荷载作用下能源桩-土力学特性研究

Study on energy pile-soil mechanical characteristics under cyclic temperature and load

开展了建筑荷载作用下能源桩-土力学模型试验及数值模拟,分析了加热(制冷)运行对桩土力学特性的影响。首先,在桩顶分级加载至2kN,待沉降稳定后再对桩土进行加热升温冷却(室温11℃→55℃→11℃),测试了桩顶竖向位移、桩身轴力、土体温度和孔隙水压力、地表竖向位移,分析了循环温度作用下的桩-土力学特性及变化规律;其次,以模型试验为原型,利用ABAQUS软件建立能源桩桩-土计算模型,并将模拟结果与试验结果对比;最后,开展了不同循环温度作用和循环次数下的桩-土力学特性数值模拟。结果表明:在运行工况下,土中超静孔隙水压力随温升的增加而变大,使土体发生热固结现象;随循环次数的增加,桩顶及地表产生不可恢复的变形,且土的沉降大于桩体沉降,导致桩身多处出现负摩阻力,且负摩阻力随温度的升高而增大。

The model tests and numerical simulations of energy pile-soil mechanical characteristics under the action of building loads were carried out, and the influence of heating(cooling) operation on the pile-soil mechanical properties was analyzed. Firstly, the pile top was loaded to 2 kN gradually. After the settlement stabilized, the pile soil was heated and cooled changing(from room temperature of 11℃ to 55℃ and the back to 11℃). The vertical displacement of the pile top, the axial force of the pile body, the soil temperature, pore water pressure and vertical displacement of the ground surface were tested, the mechanical characteristics and changes of piles-soil under cyclic temperature were analyzed. Secondly, the model test was used as a prototype, and the energy pile-soil calculation model was established by using ABAQUS software. The simulation results were compared with the test results. Finally, numerical simulations of the mechanical properties of the pile-soil under different cyclic temperature and cyclic times were carried out. The results show that: under operating working conditions, the super-static pore water pressure in the soil increases with the temperature rise, which causes the soil to undergo thermal consolidation;as the number of cyclic times increases, the pile top and the ground surface undergo unrecoverable deformation, and the settlement of soil is greater than the settlement of piles, resulting in negative friction resistance in multiple places of the pile body, and the negative friction resistance increases with increasing temperature.