Projected area-based strength estimation for jointed rock masses in triaxial compression

Reliable evaluation of the strength of rock masses is required for failure analysis in rock engineering. This paper describes the failure of rock mass specimens under triaxial compression via numerical testing based on the Discrete Element Method (DEM). It investigates the fracturing phenomena in rock masses with pre-existing joint sets and outlines a simple yet practical method for estimating compressive strength under complex joint geometric and loading conditions. The simulations capture different failure regimes, including intact, sliding and orthogonal failure, as joint geometric parameters are varied. Sensitivity studies demonstrate that the joint orientation, joint radius and continuity factor are essential geometrical terms affecting the material strength. The results reveal a linear relationship between the projected area of joint transections - which is introduced as a proxy to represent the three geometrical parameters - and the vertical strength. Based on this finding, a hypothesis for failure of jointed brittle materials is proposed, prescribing the influence of two factors: the complexity of the joint configuration and the spacing between the sample surface and the joint network. Such an approach, if validated, provides practitioners with a simple method for rapid estimation of compressive strength of rock-like materials via measurements of the joint geometry.