桩周土开挖状态下桩基础荷载传递规律研究

Study on loads transmitted laws of the existing building piles caused by soil around piles excavation

桩周土的开挖和桩身的暴露会导致桩承载力和稳定性的降低,严重时会影响建筑物安全;揭示桩周土开挖时桩基础荷载传递规律,可以为既有建筑地下空间的开发和利用提供重要的理论和技术支持。文章采用ANSYS有限元程序对一座框架结构建筑物桩周土开挖过程中的桩身轴力、侧阻力和端阻力的分布和变化规律以及桩基础的沉降变化规律进行数值分析。结果表明:随着托换桩桩周土开挖深度的增大,建筑物荷载通过侧阻传入土体比例减小,端阻和侧阻力作用充分发挥,最终桩基承载力达到极限状态,桩基沉降量会增大;增大桩长、桩径、桩数量和桩土间摩擦系数等措施可以增加桩身承载力,也可减小桩基沉降,而且增大桩身长度对提高桩基承载力效果最好,增大桩径和桩数量对减小桩基沉降效果明显。

Soil excavation and exposure around the pile will decrease the stability and even threaten the building safety. By revealing the transmitting mechanism of the foundation loas, it will provide theoretical and technical support to development and use of the undergrand space of existing buildings. The finite element analysis based on ANSYS are established to study the laws of loads transmitted from side resistance and end resistance of the piles to the soil and changes of pile settlements. The conclusions are as follows: In the phase of digging soil, with the proportion of side resistance of the piles decreasing, the side resistance and end resistance of the piles increase sufficiently. Finally, the pile reachs the stability, while the pile settlements increase. With the increase of length, diameter, number, friction coefficient of the pile, the proportion of side resistance of the piles increases which enlarge the safety of the piles. Those facts can also reduce the settlements of the pile. Length of the pile is the most effective factors to increase thestability of the piles. Diameter and number of the pile are effective factors to reduce settlements of the pile.