Fracture Process and Failure Characteristics of Sandstone with Different Height-to-Diameter Ratios

Abstract

The mechanical properties of rock materials significantly depend on their size due to their heterogeneity and the spatial randomness of joint development—a factor often neglected in pillar design and stability analyses within mining engineering. The rock samples examined herein were 100 mm in diameter and 100 mm, 200 mm, or 300 mm in height. This research analyzed the respective mechanical phenomena and failure patterns of rock specimens with varying height-to-diameter ratios under uniaxial compression. The experiment showed that the greater the height-to-diameter ratio, the smaller the elastic modulus and compressive strength. Remarkably, as the height-to-diameter ratio grew, the failure forms of the samples transitioned from splitting to shearing, while their peak strength gradually diminished. Specifically, a hike from 1:1 to 3:1 in the height-to-diameter ratio led to a roughly 20% decrease in peak strength. Utilizing the real rock fracture process analysis system (RFPA3D), the fracture processes and failure characteristics of rock specimens with dissimilar aspect ratios were comparatively explored from a microscopic viewpoint, with acoustic emissions revealing the entire process from crack initialization to penetration. The failure analysis affirmed that the simulation results corresponded closely with the experimental findings. The resultant research can offer theoretical support for the multiscale mechanical properties, fracture processes, and prediction of rock failure in mining engineering.