劲性复合桩是在水泥土搅拌桩中沉入刚性桩形成的一种新型复合桩型。为研究其在复杂软弱土-砂土地基中的承载特性，基于有限元软件ABAQUS建立劲性复合桩数值分析模型，分析芯桩长度和直径、水泥土桩长、直径和弹性模量、水泥土-预应力高强混凝土桩界面以及水泥土-土体界面剪切强度对其承载性能的影响规律。结果表明：劲性复合桩承载性能和经济优势显著；复合桩承载力随各研究参数增大而不断增大，但超过一定范围后，改变研究参数对承载力的提升有限；随着荷载增加，复合桩轴力分布曲线的斜率不断增大，PHC（pre-stressed high-stength concrete）芯桩承担的荷载比例为93.32% ~ 95.40%；当荷载超过4 000 kN后，水泥土桩在深度10 ~ 16 m范围内轴力急剧增大，芯桩／水泥土桩轴向应力比在深度约10 m附近发生明显突变；研究成果可为劲性复合桩的工程设计及应用提供参考。

The stiffly-expanded composite pile is a new type of composite pile formed by sinking rigid pile in cement soil mixing pile. In order to study its bearing characteristics in complex soft soil-sandy soil foundation, a numerical analysis model of rigid composite pile was established based on finite element software ABAQUS, with the effect of core pile length and diameter, soil-cement pile length, diameter and elastic modulus, as well as soil-cement and pre-stressed high-strength concrete(PHC) pile interface and soil-soil interface shear strength on the bearing performance was analyzed. The results show that the bearing capacity and economic advantages of the stiffened composite pile are obvious. The bearing capacity of composite pile increases with the increase of research parameters, but the improvement is limited by changing the research parameters beyond a certain range. With the increase of load, the slope of axial force distribution curve of composite pile increases, and the load proportion of PHC core pile is about 93.32% ~ 95.40%. When the load exceeds 4 000 kN, the axial force of soil-cement pile increases sharply within the depth range of 10 ~ 16 m, and the axial stress ratio of core pile/soil-cement pile changes significantly near the depth of about 10 m. The research outcomes could provide references for the engineering design and application of the stiffly-expanded composite piles.