基于圆柱面与幂函数形式曲面的复合滑裂面假设,利用克服土体重力和破坏面摩阻力的极限平衡法,推导出扩底桩在均质和分层地基中极限抗拔承载力的计算公式。假设滑移面下部为与扩底直径相同的圆柱型破坏面,上部为幂函数形式的曲面,且与圆柱面相切,在地表面与水平面呈(?/4-?/2)角度破坏。利用Matlab实现该简化公式的数值积分程序编制,并以工程实例验证上述简化公式,计算结果与工程实测结果较为接近。提出的简化计算公式可为扩底桩的抗拔承载力的计算提供依据。 Based on the assumption of composite sliding surface between cylindrical surface and power function surface, the ultimate pullout capacity of expanded bottom piles in homogeneous and stratified subsoil is deduced by means of the limit equilibrium method that overcomes the friction of soil mass and failure surface formula. It is assumed that the lower part of the slip surface is a cylindrical failure surface with the same diameter as the expanded bottom. The upper part is a power function surface and tangential to the cylindrical surface, destroying the ground surface and horizontal plane at (? / 4 -? / 2) angles. The numerical integration program of the simplified formula is realized by Matlab, and the above simplified formula is verified by an engineering example. The calculated result is close to the measured result of the project. The proposed simplified calculation formula can provide the basis for the calculation of anti-pull bearing capacity of pedestal pile.