Abstract
In this study, considering the scale effect of rock mass, the influence of different height‐to‐diameter ratios on rock mechanics and acoustic emission characteristics was studied by using PFC2D software. The damage constitutive model of rock was established, and the damage evolution characteristics of rock with different height‐to‐diameter ratios were further analyzed. The results showed that, with the increase of height‐to‐diameter ratio K, the uniaxial compressive strength and peak strain of rock exhibited a gradual decrease; however, the elastic modulus gradually increased. Moreover, rock failure modes exhibited different characteristics under different K values. The scale effect showed little influence on the acoustic emission characteristics in the elastic stage; nonetheless, in the plastic deformation stage and the residual damage stage, with the increase of the rock’s height‐to‐diameter ratio, the maximum number of impacts of acoustic emission increased, the range of strong strain of acoustic emission decreased, and the maximum time of acoustic emission impacts increased gradually. The height‐to‐diameter ratio of the rock slightly influenced the zero‐damage stage of the rock, but the damage affecting the rock increased slowly and accelerated the development stage. The damage evolution law was found to be similar when the K values varied from 1.0 to 2.0; however, when the K was greater than 2.0, the damage evolution law exhibited the characteristics of slowing down in the acceleration phase.
Highlights
With the development of economy and the increase of the expansion scale of underground space in China, the geological disasters related to rock mass instability, such as tunnel rock burst and mine rock burst, are becoming progressively more serious [1,2,3,4,5,6,7,8,9,10]
Significant research efforts have been devoted to the study on the size effect of rock mechanics
Liang et al [18] believed that the size effect of rock mass includes the size effect of intact rock mass and the size effect of jointed rock mass, but there is no organic connection between them. erefore, they proposed a multi-scale rock mass engineering calculation method at the micro level and the macro level and established a relationship between the two scale effects
Summary
With the development of economy and the increase of the expansion scale of underground space in China, the geological disasters related to rock mass instability, such as tunnel rock burst and mine rock burst, are becoming progressively more serious [1,2,3,4,5,6,7,8,9,10]. E above-mentioned studies are of great significance for understanding the damage characteristics of rocks under different scale conditions; the size effect of rock mechanics properties is of great complexity, which is still a subject worthy of further study at present. Accompanying the size effect of rock mechanics, the acoustic emission characteristics of rocks should have different characteristics; research in this area has rarely been reported. First different height-to-diameter ratios were considered by using the numerical simulation software, namely, the particle flow code in two dimensions (PFC2D) [28, 29] to study and analyze the rock mechanics and acoustic emission characteristics, and a rock damage constitutive model was constructed based on the acoustic emission characteristics. The rock at different scale law of damage evolution was analyzed. e research results have certain significance for further understanding the size effect of rock mechanics and preventing and controlling rock engineering disasters
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