目前工程与研究从点云中提取的横截面变形指标仍以收敛变形为主，难以反映接头作用下盾构隧道结构“分段连续”的变形特征。为从点云中充分挖掘盾构隧道横截面变形特征，提出从三维点云提取位移场并通过位移场表征盾构隧道结构横截面变形的方法。该方法以接头为界对盾构隧道每块管片的轮廓分别在极坐标系使用傅里叶函数拟合，对各期点云拟合后的曲线按相同密度划分网格，并将网格节点处的坐标相减，求得衬砌结构各管片位移场。通过整环足尺试验与数值模拟，分别验证该方法提取径向、切向变形的可靠性。通过理论分析与数值试验，讨论该方法应用过程中拟合函数、测量误差、参考系选取等关键因素对变形提取结果的影响。结果表明： 1）用于拟合的傅里叶函数阶数越高，拟合管片轮廓越精细。 2）在测距误差作用下，使用高阶数的傅里叶函数易产生过拟合现象，增加变形提取误差。3）通过工程示范展示该方法在实际盾构隧道工程中的应用效果，证明了其用于实际工程的可行性。

In current engineering and research, the indices of cross-sectional deformation extracted from point clouds are primarily convergent deformation, which can hardly reflect the deformation characteristics of sectionally continuous deformation properties of shield tunnel linings under the action of a joint. To fully extract the cross-sectional deformation characteristics from point clouds, a deformation characterization method, which takes joints as boundary to fit each segment separately in a polar coordinate system using Fourier functions, is proposed. The fitted curves of each segment are then meshed based on the same density, and the node coordinates are tracked to derive the displacement field of each segment. Full-scale experiments and numerical models are used to validate the reliability of this method. In addition, theoretical analysis and numerical experiments are conducted to examine the influence of key factors (such as the types of fitting functions, influence of measurement errors, and selection of reference system) on deformation extraction results. The findings reveal the following: (1) The higher the order of the Fourier function used for fitting, the more detailed the fitting of the segment lining profile. (2) Under the effect of measurement errors, the application of high-order Fourier functions is susceptible to overfitting, which results in an increase in the deformation extraction error. (3) The proposed method shows its effect and feasibility in actual shield tunnel engineering.