Experimental and numerical study on crack propagation and deformation around underground opening in jointed rock masses
Understanding the process of crack propagation and deformation around underground openings is a key issue in several engineering fields, such as tunneling, mining, and radioactive waste disposal facilities. Many failures of underground openings are commonly induced by the geological discontinuities of host rock masses, which contain the existing discontinuities and the new cracks generated during the construction of underground structures.
In this study, base friction tests were conducted to investigate the influence of dip angle of layered joints on the stability of circular openings in jointed rock masses and a series of numerical simulations utilizing an originally developed code based on distinct element method (DEM) were performed on the experimentbased and extended numerical models, respectively.
The results show that the main propagation direction of newly generated cracks is approximately perpendicular to the joint dip angle. For the brittle host rock masses, the deformation around the underground openings is governed by the tensile failure of host rock masses. A decrease in joint dip angle gives rise to an increase of plastic failure zone in the host rock masses. The models with lower joint dip angles could generate a larger number of cracks. The maximum displacement observed at the left shoulder of openings is approximately 1.8–2 times of the minimum displacement at the right side wall of circular opening.
The influences of the opening shape on the main propagation direction of newly generated cracks could be negligible. Due to the stress concentration at the sharp corner of square openings, a larger area of plastic zones is developed, which leads to obvious increment of displacements around the underground openings.
Keywords: geological discontinuity, base friction test, distinct element method, numerical analysis, joint spacing.