Structural planes surveying and fractal dimension characteristics of tunnel face based on digital photogrammetry

Abstract

Based on the digital photogrammetry, technical operation standards, such as the layout of the controlling points and optimization of shooting area, and some technical essentials have been proposed. Thus, the tunnel excavation contour and joint parameters can be obtained rapidly and accurately without interfering with tunneling operations. For practical tunnel engineering, the three-dimensional models of 62 tunnel working faces have been established, and then the overbreak and underbreak data and the joint parameters have been collected by Siro 6.0, an artificial-intelligent interaction platform. Based on the statistical self-similarity of tunnel section contour and the method of box dimension, the relationship between the fractal dimensions and the surrounding rockmass classifications, orientation, joint spacing, and included angle between joint strike and tunnel axis has been analyzed. The result shows that the fractal dimension reduces with decrease of the surrounding rockmass classification. When the joint spacing is fixed, the fractal dimension shows exponential decay with the increase of included angle between joint strike and tunnel axis. When the angle is fixed, the fractal dimension decreases with the increase of joint spacing. For the surrounding rockmass of classification III, the relationship between the fractal dimension and joint dip angle is approximately normally distributed and the fractal dimension reaches the maximum value as the joint dip angle ranges from 35° to 55°. In addition, the fractal dimension decreases linearly with the increase of joint spacing, presenting two segments divided by the intersection with joint spacing equal to 32.65 cm.