APPLICABILITY OF A TUNNEL DEFORMATION ESTIMATION FROM A POINT CLOUD ADOPTING ELLIPTIC FOURIER ANALYSIS

Abstract

 The estimation of tunnel deformation from the change in the profile is expected to improve the efficiency of inspection. This paper considers the applicability of a tunnel deformation estimation from a point cloud adopting elliptic Fourier analysis. Tunnel deformation is estimated from the difference in the Fourier series representations of the outline before and after deformation. The deformation of a Shinkansen tunnel calculated in the numerical analysis is estimated to evaluate the method’s accuracy. The numerical results show that the estimation of the normal displacement is highly reliable, with the estimation error being roughly proportional to the measurement error. The estimated displacement fluctuates around the true value. In contrast, the reliability of the estimation of the tangential displacement tends to be low because this displacement does not contribute to the change in the outline. The estimation error increases rapidly with the measurement error, and the estimated displacement tends to be independent of the true value. The proposed estimation method is applicable even when the outline is not closed.