Stress intensity factors and T-stress for the center-cracked Brazilian disk under combined confining and non-uniform pressure

Rock masses in deep earth, deep sea, and deep space environments are often subjected to confining pressure. Considering the effects of confining pressure and friction on crack surfaces, closed-form solutions for mode I and mode II stress intensity factors and T-stress of a center-cracked Brazilian disk subjected to combined confining pressure and non-uniform pressure are presented using weight function method. The convergence of these closed-form solutions is assessed, and the recommended summation coefficients for a given truncation error are provided. Using the derived closed-form solutions, the stress intensity factors and T-stress of the center-cracked Brazilian disk under various loading conditions are calculated, and the effects of loading angle, crack length, contact angle, confining pressure, and friction coefficient on the stress intensity factors and T-stress are analyzed. Furthermore, the critical loading angle θ c for the transition of the center-cracked Brazilian disk specimen from tensile-shear fracture to compressive-shear fracture under combined confining pressure and non-uniform pressure is also given. The results indicate that confining pressure and crack-surface friction suppress both mode I and mode II fracturing of the center-cracked Brazilian disk specimen. When the loading angle is small and the contact angle is large, the influence of contact angle on stress intensity factors and T-stress should be taken into account.