In this paper, the effect of the ratio of tensile strength to confining pressure on the penetration of U Shape disc has been investigated using Discrete Element Method. For this purpose, three numerical models with different tensile strength of 5 MPa, 15 MPa and 25 MPa were built. From each model two similar samples were prepared and compressed by two different confining pressures of 5 MPa and 25 MPa, respectively. The U shape cutter penetrates in the model by the rate of 0.02 m/s till 4 mm of disc is penetrated. In total, 6 simulations have been done. The rock materials, below the cutters, show three different mechanical behavior including failure, plastic and elastic behavior. The failure zone is fully fractured while the plastic zone is consisted of partially micro crack with several major fractures. The elastic zone has remained undamaged. The effect of the ratio of tensile strength to confining pressure has substantial effect on the extension of three introduced zones. When tensile strength is 5 MPa, the initiation force and failure stress is increased by increasing the tensile strength but the extension of failure zone and chipping thickness is decreased. When tensile strength is 25 MPa, the initiation force, failure stress, extension of failure zone and thickness of chipping is constant by increasing the tensile strength.