CNOOC Ltd. Hainan
School of Petroleum Engineering, China University of Petroleum (East China)
College of Civil Engineering, Taiyuan University of Technology

【目的】阶梯桩是在等截面桩的基础上改进而来的新桩型,但其受力变形相对复杂,对其侧摩阻力、变截面端阻力及桩端端阻力的发挥过程还不清晰。【方法】通过室内模型试验,采用分级荷载施加法对等截面普通桩和阶梯桩竖向承载性能进行研究。【结果】试验结果表明:在同等条件下,阶梯桩相对于等截面桩降低了33%的沉降,阶梯桩的单方极限承载力比等截面桩提高了19%,说明阶梯桩有减小沉降的优势且单位体积材料发挥得更好;阶梯桩桩身轴力在变截面处发生突变,表明变截面处的端阻力会影响轴力传递;加载初期,随着桩顶荷载的增大,侧摩阻力占桩顶荷载的比率逐渐增大,变截面端阻力以及桩端端阻力分担比率逐渐减小;当侧摩阻力达到极限值后,侧摩阻力占桩顶荷载的比率逐渐减小,桩端端阻力与变截面端阻力分担比率逐渐增大,而变截面处端阻力所占比率最先趋于平稳,表明变截面下方土体最先发生破坏。根据太沙基理论修正了阶梯桩变截面端承力计算公式,并与试验结果进行对比,验证了此理论方法的可靠性。

【Purposes】 The stepped pile with variable cross-section is a new pile type that is im⁃ proved on the basis of the pile with equal cross-section, but its loading and deformation are relatively complex, and the processes of exerting lateral friction resistance, end resistance at variable section, and pile end are not understood. 【Methods】 In this paper, the vertical bearing capacities of ordinary pile and stepped pile were studied by indoor model tests with the graded load application method. 【Findings】 Under identical conditions, the settlement of the stepped pile is reduced by 33%, and its bearing capacity of unit volume is increased by 19% compared with those of the pile with equal cross- section, indicating that the stepped pile has the advantage of reducing the settlement and better bearing capacity of unit volume. The axial force of the stepped pile decreases sharply at the position of the vari⁃ able cross-section. It is shown that the existence of a variable section affects the axial force transfer of the stepped pile. In the initial stage of loading, as the load on the pile top increases, the ratio of the lat⁃ eral friction resistance to the load on the pile top gradually increases, and the ratio of end resistance at the variable cross-section and the end to the load on the pile top gradually decrease; When the lateral frictional resistance reaches its limit, the ratio of the lateral frictional resistance to the pile top load gradually decreases, and the ratio of the end resistance at the variable cross-section and the end gradu⁃ ally increases, but the ratio of the end resistance at the variable cross-section tends to be stable first, which indicates that the soil at the variable cross-section is destroyed first. According to the Terzaghi theory, the formula for calculating the end bearing capacity at the variable cross-section of stepped piles has been revised, and the reliability of this theoretical method has been verified by comparing it with experimental results.

国家自然科学基金资助项目(52078483)

刘书杰,刘正,王腾,等.阶梯桩竖向承载性能模型试验研究[J].太原理工大学学报,2025,56(2):199-206.

LIU Shujie,LIU Zheng,WANG Teng,et al.Model test study on vertical bearing capacity of stepped piles[J].Jour⁃nal of Taiyuan University of Technoloty,2025,56(2):199-206.