Experimental Investigation of Bedding Plane Orientation on the Rockburst Behavior of Sandstone

Abstract

Rockburst is a violent rock failure process which poses a significant threat to human safety in mining and tunneling construction. Although many in situ investigations provided valuable insights on the rockburst mechanism, the failure and rock fragmentation process during a rockburst cannot be fully examined on the site. In this paper, a modified triaxial rock testing apparatus is employed to investigate the rockburst behavior of oriented sandstone. A high-speed camera is used to record the crack propagation and the ejection of rock fragments on the unloading surface. The microscopic characteristics of the fragments generated from the rockburst tests are observed using the scanning electron microscope (SEM) imaging technique. The trajectory sketches are drawn to calculate the initial velocities of the rock fragments ejected based on the photographs taken by the high-speed camera. The results show that the mass and velocity of fragments are the two main parameters for the identification of the energytransferring process in the rockburst test. When the bedding orientation is perpendicular to the unloading surface, the rockburst is controlled by the specimen's strength. However, when the bedding orientation is parallel to the unloading surface, the rockburst is dependent on the structural stability of the specimen.

Investigation of Macroscopic Brittle Creep Failure Caused by Microcrack Growth Under Step Loading and Unloading in Rocks

“…The theoretical results are similar to triaxial unloading experiment results of studies in which the delayed rockburst of surrounding rock was studied during underground quarrying (He et al 2010(He et al , 2012. The findings assist in understanding deformation behavior and time-delayed rockburst mechanism for surrounding rock during underground excavations.…”

Experimental and theoretical study of the anisotropic properties of shale

“…Different failure modes may occur under a foundation at slopes depending on boundary condition and the inclination of weak planes for inherently anisotropic rocks [38]. Bedding plane orientation changes the rockburst behavior in mining and tunneling construction [39]. Shear stress concentration usually exists near the interface between weak planes and the matrix of the rocks, and this may easily result in shear slippage or damage [40].…”

Influence of strain energy released from a test machine on rock failure process

“…Because of the complex boundary conditions and the interaction between different loading components of a test machine, Hudson et al (1972) LSS of test machines nowadays can be made relatively high; however, it is still finite and the test machine can store strain energy in the pre-peak deformation stage of rock and release the energy in the post-peak deformation stage. Therefore, it was speculated in laboratory testing that violent rock failures observed during testing hard rocks could be primarily attributed to the sudden release of strain energy from the test machines (He et al 2012;Zhao and Cai 2014), rather than to the unceasing displacement of the loading ram when the servo-controlled loading method was employed (Rummel and Fairhurst 1970). Apparently in reality, it is difficult to shut down the energy supply of a test machine to the loading ram fast enough during the process of unstable rock failure, as a means of confirming that it is the strain energy released from the test machine that primarily contributes to unstable rock failure.…”