深开挖基坑回弹引起的坑中桩受力与位移计算

A Calculation of Behavior of Underpinning Pile Subject to Excavation of Deep Foundation Pit

摘要:

深基坑开挖卸载坑底土回弹会对坑底桩的受力性状产生影响.在不考虑桩身自重的情况下以残余应力法和Mindlin解为基础,以桩土位移协调和桩体受力平衡为条件,研究刚性桩桩体回弹量和桩侧摩阻力分布.分析结果表明,桩体的位移量随着桩长和桩径的增长而减小,桩径的变化对中性点的深度位置以及桩侧摩阻力的分布形态影响很小.中性点随着桩长的增加其深度位置逐渐下移.当桩长相对较短时,桩体的位移量随着基坑开挖深度的增加为增大；当桩长相对比较长时,桩体的位移量随着基坑开挖深度的增加而增大,最后出现平缓的趋势.中性点随土体回弹再压缩模量的增大而下移,桩体回弹量随土体回弹再压缩模量的增加而减小,后趋于定值.

Abstract:

Behavior of underpinning pile foundation is affected by unloading and rebound subject to deep excavation.Based on residual stress method and Mindlin solution,an analysis was made of the rebound of rigid pile and the distribution of shaft resistance under the condition of displacement compatibility and pile’s force balance when pile’s self weight was neglected.Analysis results indicate that pile’s displacement decreases as its length and diameter increase.Changes of pile’s diameter have little impact on the depth of neutral point and the distribution pattern of shaft resistance.The neutral point is becoming lower as pile length is increasing and the same with the rebound and recompression modulus.The rebound of underpinning pile increases as excavation depth increases and becomes gradual when pile length is relatively longer.Pile’s displacement decreases and then reaches a certain value as the modulus of soil rebound and recompression increases.