Influence of Height–Diameter Ratio on Rock Compressive Failure Characteristics and Damage Evolution Law

Abstract

In underground projects such as mining and tunneling, the presence of coal rock columns plays a certain supporting role, and the instability of coal rock columns is often related to their size and shape of presence. Therefore, in order to investigate the compressive damage characteristics and damage evolution law of rocks of different sizes, uniaxial compression tests were conducted on sandstones with different height−diameter ratios to explore the mechanical properties and damage characteristics of sandstones with different height−diameter ratios, analyze the connection between acoustic emission ringing count rate, accumulated energy, peak frequency, and b-value changes and height–diameter ratio, and analyze the evolution law of sandstones during damage based on damage variables, and draw the following conclusions. As the height-to-diameter ratio increases, the less affected by the end effect, the rock strength shows a nonlinear decreasing trend, and the decreasing trend becomes slow. The acoustic emission ringing count rate evolved from intermittent to continuous occurrence, showing multiple peaks as the test proceeded. The accumulated energy rises sharply before rupturing after several steps from stable development. As the height-to-diameter ratio increases, the acoustic emission signal before rupture rises more intensively, and the damage is more concentrated. The overall level of the b-value shows an increasing trend, the proportion of acoustic emission high-frequency signal gradually increases, and the development of tiny cracks inside the rock more intensively. Therefore, the sudden change of acoustic emission signal can be used as a precursor of rock damage. The rock damage curve has smaller values in the stable damage phase. With the increase in the height-to-diameter ratio, the non-stable damage stage damage showed a trend of decreasing and then increasing and reached the minimum at L/D = 2.0.