Compared with the conventional pile foundation,the slendemess ratio of root pile is slightly larger (generally greater than 30) , which is characterized by great superficial friction and the frictional resistance always plays a vital part in bearing capacity. Therefore,there must be the critical length for the root pile in the condition of vertical load. As mentioned above,and on the basis of the former study as well as adopting the load transfer function analysis method that is put forward by Gordon Sato,assumption that load-displacement relationship for the ideal line of plastic, the authors has analysed the load transfer characteristics of root piles under vertical load,and borrowing lateral friction resistance empirical equation put forward by Esrig.the paper has also infered the terminus long computational method under the vertical load function for root pile in homogeneous soil layer in the critical length. Meanwhile,the method may provide certain theory basis for determining the critical length in design of root pile.%树根桩不同于常规的桩基,它的长细比较大(一般大于30),具有很大的表面摩阻力,承载力主要由侧摩阻力承担.因此,在竖向荷载作用下,树根桩必然存在一个临界桩长.本文作者借鉴已有的研究成果,采用佐藤悟提出的荷载传递函数解析法,假定荷载-位移关系为理想的线弹塑性关系,分析了树根桩在竖向荷载作用下的荷载传递特性,并借用Esrig按临界状态原理分析得到的桩土界面上的桩侧阻力经验公式,推导出在竖向荷载作用下,树根桩竖直单桩在匀质土层中的临界桩长计算公式.该方法在树根桩设计时,可为单桩临界桩长的合理确定提供一定的理论依据.
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