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1. Introduction
Tunnel excavation is the most common technique in hydropower engineering, traffic engineering, mineral engineering, and so forth. Therefore, a method which can validly predict potential danger would be of significant benefit to the tunnel construction operators, since the tunnel excavation has been the most common construction activity.
In recent years, undesirable surrounding rock collapses frequently arose in tunnel excavation, which often lead to casualty. Therefore, it is urgent to develop a valid and convenient method to predict potential danger in tunnel excavation. Jimin and Mahtab [1] obtained the sizes, shapes, and locations of overbreak blocks by structural plane geometrical characteristics in the case of underground tunnels; Jiamei et al. [2] analyzed the effects of surrounding rock and support structure stability by TBM excavation from the angle of quantity; Jian and Xinjiao [3] deduced the statistical regularity of overbreak block sizes and locations in expressway tunnels; Deyun [4] proposed a calculation method of the areas of overbreak and underbreak blocks from the view of mathematics; Huibing [5] applied the drill hole blasting method to seek overbreak and underbreak block sizes and locations; Mingnian and Baoshu [6] used the self-adaption finite element method to analyze the effects of tunnel overbreak blocks on stability of surrounding rock; Revey [7] proposed a control overbreak method of mine tunnel by means of control blasting; Ibarra et al. [8–10] proposed a light-section method to evaluate the volumes of overbreak blocks and developed the relevant equipment and calculation program; Thidemann [11], Abel [12], and Martna [13] applied numerical method to analyze the interaction of tunnel overbreak blocks and surrounding rock deformation. In fact, overbreak blocks in tunnel excavation arise from two aspects: incorrect excavation and natural structural plane. However, the above-mentioned forecasting and evaluation methods only focus on the excavation factor. Goodman [14] put forward the block theory (BT), which can reflect the effect of...