考虑时间效应的不同厚度高回填场地桩基受力特性分析

为明确高回填场地回填土蠕变对桩基受力和变形的影响，基于有限差分软件FLAC3D中内置的Burgers模型，选用桩顶荷载为1MPa，桩径为2m，嵌岩深度为6m（3倍桩径），回填土高度分别为10m、15m、20m和25m的桩基，通过数值模拟的方法研究了考虑时间效应下不同厚度高回填场地桩基受力性能。结果表明：不同填土高度其对应的蠕变稳定时间也不尽相同；随着桩周填土蠕变时间的增加，各工况桩周回填土沉降随之增大最终趋于稳定；桩周回填土蠕变稳定后，增加回填土厚度，桩周回填土最终沉降、中性点深度变化、桩身最大轴力以及桩端阻力和位移均随之增大，各工况桩周回填土最终沉降、中性点深度变化、桩身最大轴力以及桩端阻力和位移均线性相关；可见高回填场地桩基设计施工中回填土蠕变以及填土厚度的变化对于该场地桩基的影响不可忽视。

Piles with Different Thicknesses and Heights in Backfill Field Considering Time Effect Analysis of Mechanical Characteristics

In order to determine the influence of creep of backfill soil on pile stress and deformation in high backfill site, based on Burgers model built in finite difference software FLAC3D, pile foundations with pile top load of 1 MPa, pile diameter of 2 m, rock-caking depth of 6 m (3 times pile diameter) and backfill heights of 10 m, 15 m, 20 m and 25 m were selected. By means of numerical simulation, the mechanical behavior of pile foundation with different thickness and high backfill site considering time effect is studied. The results show that the creep stability time of different fill heights is different. With the increase of creep time around the pile, the settlement of the backfill around the pile under various working conditions increases and finally tends to be stable. After the creep stability of the backfill around the pile, when the thickness of the backfill increases, the final settlement of the backfill around the pile, the change of the depth of the neutral point, the maximum axial force of the pile, the resistance and displacement of the pile tip all increase, and the final settlement of the backfill around the pile, the change of the depth of the neutral point, the maximum axial force of the pile, the resistance and displacement of the pile tip all have a linear correlation. It can be seen that the influence of creep of backfill soil and the change of thickness of backfill soil on pile foundation design and construction of high-backfill site cannot be ignored.