Research And Application Of Rock Cave Cracks Nondestructive Detection Based On Close Range Photogrammetry

Crack is the main disease of grotto relics. At present, nondestructive detection methods of crack are ultrasonic detection methodand resistivity micro sounding method and ground penetrating radar,etc. Affected by the environmental constraints, manual contact measurement collection information of cave cracks is time-consuming and laborious; it can not meet the rapid construction needs. Refer tothe existing acquisition scheme for rock cracks information, thispaper proposed the method of close-range photogrammetry to detect the disease of stone relics cracks,and jointed the ultrasonic detection method to research the nondestructive detection method for Yungang Grottoes surface disease. The results showed that, combined geophysical method and close-range photogrammetry method is very efficient for detecting stone relics crack, had higher practical significance in engineering and is a great development potential measuringmeans for crack disease. Through researching obtained close-rangephotogrammetry working method to quickly obtain rock cracks parameters information, and opened up a new research direction for quicklyacquiring cracks information.This paper designed the image acquisition system using the digital camera and rangefinder and other device, got better result picture data, and calibrated the camera used in the test using the plane chessboard grid target to get inside and external and distortionparameters of the camera.Fracture identification focuses on mild fissure extraction. Decomposed the collected cracks images by wavelet,we gained multi resolution image,recognized severe cracks in a lowresolution image and recognized moderate and mild cracks in high resolution image. Based on analyzing image characteristics such as g ray feature,scale feature,frequency domain feature and edge feature, put forward the corresponding image quality improving method andused Otsu, edge detection and contour extraction image processingalgorithms to accurately identify cracks in the image.Developed the recognition system taking Delphi as the development platform to extract cracks feature and recognize the rock fractures, the test showed that the system can efficiently recognize thecrack image and has good application value in practical work. Developed the recognition system taking Delphi as the development platform to extract cracks feature and recognize the rock fractures, thetest showed that the system can efficiently recognize the crack image and has good application value in practical work. We used a variety of geophysical methods to measure In Mentougou as the testing area and the Yungang Grottoes as the measured area. In contrast to the geophysical prospecting method measurement data and close-rangephotogrammetry data results, the results showed that the close-range photogrammetric technology observation precision has reached a higher level, and is a great development potential measuring means for detecting the crack disease. Combined with ultrasonic method detecting the crack depth, gave a crack's volume theoretical formula asthe theoretical basis for post grouting work.