Laboratory-Scale Rockburst Physical Model Testing Using a True-Triaxial Cell

Abstract

Assessment of rockburst risk is one of the most fundamental challenges in tunnel design and construction in rocks. The rockburst phenomenon is typically related to rock brittle failure properties, which result in significant strain-energy release, spalling, fractures, and damage near the tunnel opening. This research aims to present a preliminary analysis of rockburst in an unsupported circular tunnel using a novel experimental approach to model tunnel boring machine excavated opening through brittle fracture material. In this physical model testing, the true-triaxial cell utilizes a cube of synthetic sandstone of 300 mm dimensions with a freshly excavated 51 mm diameter tunnel, 150 mm depth on the center top side using a miniature tunnel boring machine. The six sides of the specimen cube are loaded in a true-triaxial manner, allowing for various magnitudes of principal stresses and stress levels that reflect actual in-situ conditions. In addition, the experimental setup employs acoustic emission monitoring to observe the tunnel response during excavation and loading increment. However, the sample in this preliminary experiment was loaded under hydrostatic circumstances and gradually increased until the sample showed a reduction in the acoustic emission activity and failed. The experiment results suggest that the physical model can better understand rockburst in a tunnel through the acoustic emission analysis. The model can outline the damage and spalling during strain energy release near the tunnel boundary.