根据桩 土侧向变形及竖向变形协调条件 ,应用弹性理论导出了桩及桩周土的应力 应变关系 ,得出了桩体材料屈服时桩 土应力比的计算式。推出了桩周土处于极限平衡状态下 ,碎石桩极限承载力计算式。指出用碎石桩加固软土地基其效果比较明显 ,但加固土的变形模量大于 8MPa的地基 ,效果不很明显。并通过工程实例 ,将本文计算结果与实验结果作了对比 According to the lateral deformation and vertical deformation of pile-soil, the stress-strain relationship between pile and soil around the pile is derived by using elastic theory, and the formula of pile-soil stress ratio is obtained when yielding. The formula of ultimate bearing capacity of gravel piles under extreme equilibrium condition is introduced. It is pointed out that the effect of using soft gravel pile to reinforce soft soil foundation is obvious, but the deformation modulus of reinforced soil is larger than 8MPa, the effect is not obvious. Through the engineering example, the calculation results and the experimental results are compared