Method and device for measuring tunnel lining cracks

Abstract

The invention relates to a method for measuring tunnel lining cracks. The method comprises the following steps of: acquiring an image of a crack by a digital camera and measuring the acquisition distance by a laser ranger; selecting an area needing to be measured from the acquired image so as to prevent processing deviation due to excessively big picture and relatively small target crack, and changing the selected area into a gray image; determining a threshold for the selected gray image and performing binarization image division to obtain a target area; extracting a white area only comprising the crack from the target area; extracting the border of the crack to obtain a border graph; calculating the pixel width of the crack by a minimum distance method; and obtaining the actual width ofthe crack according to a predetermined calibration proportion between the actual pixel size and the photographing distance. The method has the advantages of low cost, high speed, convenient carrying and high measurement precision.

Description

technical field [0001] The invention relates to a tunnel lining crack measurement technology, in particular to a tunnel lining crack measurement method and a measurement device thereof. Background technique [0002] Quantification of defects such as cracks has always been the goal of non-destructive testing. With the advancement of detection technology, the traditional method of measuring the crack width by human eyes or using a simple instrument such as a reading magnifying glass to estimate, due to the high subjectivity of its personnel, and low accuracy and efficiency, will Gradually replaced by new methods. With the rapid development of computer technology and the continuous improvement of related theories, digital image processing technology has been widely valued in many application fields and has achieved significant pioneering achievements. The photogrammetry technology based on digital image processing has penetrated into the fields of civil engineering such as cr...

AI Technical Summary

Problems solved by technology

In the tunnel, for images of high-level cracks that cannot be touched, the process of hand-held contact acquisition is cumbersome

However, images taken at long distances are sensitive to noise and light, which seriously affects image quality and makes subsequent image preprocessing difficult and complicated.

The area ratio of cracks in long-distance images is much smaller than that in contact images, leaving a large area of ​​complex and changeable background images, coupled with the defects of some edge detection methods, making close-up The edge extraction method for medium and wide cracks is not applicable, and a suitable new method needs to be found

In addition, unlike the contact measurement with a fixed distance, the randomness of the location where the crack occurs leads to the randomness of the shooting distance. It is necessary to find a new calibration method to replace the traditional fixed-distance calibration

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