Experimental Investigation of the Joint Geometry Effects on the Mechanical Behavior and Confined Compressive Strength of Jointed Rock Masses

Abstract

This article investigates the role of joint geometrical characteristics, including orientation, filler thickness, and roughness type, on the confined compressive strength of jointed rock masses. A series of comprehensive laboratory experiments was designed and conducted to achieve this. In the first stage, limestone rock samples were used according to the experimental design. Using a cutting machine, two samples were prepared with wavy and ribbed artificial roughnesses at different angles of 0, 30, 45, and 60 degrees. Gypsum and cement filler materials with specific resistances in thicknesses of 3, 5, and 8 mm were utilized to examine the effect of filler material thickness. After triaxial laboratory tests were performed with a hook cell device at two confining pressure levels (5 and 14 MPa), the following key results were obtained: (a) higher confining pressures (14 MPa) significantly enhance compressive strength, with ribbed joints showing a more pronounced response than wavy joints, (b) for both roughness types, compressive strength was lowest at a 30-degree angle, highest at a 0-degree angle, and intermediate at a 60-degree angle, confirming the effect of anisotropy, and (c) thicker fillers generally improved strength at lower pressures but were less effective at higher pressures. These findings emphasize the importance of considering pressure conditions, joint orientation, and filler thickness in optimizing the mechanical behavior of jointed rock masses.