To monitor the strain of a full-section rock tunnel boring machine cutterhead under harsh working condi-tions,a visual recognition method for surface strain reconstruction is proposed.This paper details the process of ob-taining actual deformation of the gauge length by measuring the change in pixel count between the center points of circular gauge lengths in the image.Based on these measurements,surface stress is reconstructed using the Cauchy-Green formula.Focusing on two key positions,the tunnel boring machine cutterhead and the rib plate,the study designed two standard samples of different sizes using 4330V and Q345-D materials.Two measurement sys-tems,one based on visual recognition and the other on strain gauges,were constructed to compare strain under ten-sile load and to reconstruct the surface stress of the samples.The error range for the deformation of standard parts made of the two materials,measured using the visual recognition method,was 1.28%～3.23%.Subsequently,through the proposed method,surface strain reconstruction was conducted for the 4330V materials,with an error range of 2.20%～4.76%.The results demonstrated that this method could achieve accurate measurement of de-formation and multidirectional strain and deformation reconstruction,providing a solid foundation for the strain and deformation measurement of complex structures.
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