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在28℃,28℃→55℃,28℃→55℃→28℃三种工况下,开展宁波饱和黏土中热交换桩承载力特性模型试验研究,先对桩土加热(降温),再进行静载荷试验,测定土体的温度和孔隙水压力、地表沉降及桩顶位移、桩身轴力和荷载–沉降试验数据,研究土体的热固结过程及桩负摩阻力的形成机制;其次,以模型试验为原型,利用Abaqus软件建立了考虑热流固耦合作用的桩–土有限元模型,将计算结果与试验结果进行对比验证,进而讨论温度对桩身轴力和桩侧摩阻力的影响,结果表明:加热升温后,桩、土发生膨胀变形,土中出现超静孔隙水压力;随着孔压的消散,土体发生热固结现象,且其固结沉降量大于桩体沉降量,地基最终表现为沉降变形,而桩侧出现下拉荷载,产生负摩阻力;随温度的升高,沿深度方向,桩身轴力衰减,热固结后土体的强度有所提高,桩侧摩阻力增大,单桩极限承载力随温度的升高而增大。
Under the three conditions of 28 ℃, 28 ℃ → 55 ℃, 28 ℃ → 55 ℃ → 28 ℃, the model test of bearing capacity of heat exchange pile in saturated clay was carried out. The pile soil was heated (cooled down) Static load test, soil temperature and pore water pressure measurement, surface subsidence and pile top displacement, pile axial force and load-settlement test data to study the thermal consolidation process of soil and pile negative friction resistance mechanism; secondly Based on the model test, a finite element model of pile-soil considering the effect of thermo-fluid-mechanical coupling was established by using Abaqus software. The calculated results are compared with the experimental results, and then the influence of temperature on the axial force of the pile and the lateral friction of the pile The results show that after heating, the pile and soil expand and deform, and the excess pore water pressure appears in the soil. With the dissipation of pore pressure, thermal consolidation occurs in the soil, and the consolidation settlement is larger than the settlement of the pile , The ultimate subsidence of the foundation is subsidence deformation, while the pile side has a negative pull load, resulting in a negative frictional resistance. Along with the increase of temperature, along the depth direction, the axial strength of pile body decays and the strength of soil body increases after heat consolidation. Frictional resistance increases, the ultimate bearing capacity of single pile with temperature Increases increases.