In this paper, the effect of cable indent shape on the shear behavior of concrete-cable attachment surface has been investigated using PFC2D. Firstly, calibration of PFC was performed using the Brazilian experimental test and uniaxial compression test to reproduce the concrete sample. After calibration of PFC2D, punch shear tests were simulated by creating a rectangular concrete model in PFC2D. Numerical models with a dimension of 100mm *100 mm were prepared. cable with different indent shape was inserted within the model. The punch shear test condition was added to the model. The normal load was fixed at 3. 7 MPa (σ c/10) and shear load was applied to the model till failure occurred. The results show that tensile cracks are the dominant mode of failure that occurs in the attachment surface. Also, the shape of the attachment surface has an important effect on the failure mechanism of concrete. The shear strength increased by increasing both of the bolt indent width and length.

In this paper, the effect of PDC cutter angle on the failure mechanism of rock like materials was investigated using experimental test and numerical simulation. For this purpose, three PDC cutter with different angle were built, i. e. 0° , 30° and 60° . Nine gypsum sample with dimension of 14cm*11cm*5cm were prepared. The ratio of gypsum to water was equal to 2. For each PDC angle, three similar gypsum blocks were tested. The blocks were situated above the PDC cutters and these assemblies were fixed in Uniaxial test machine. The loading rate was 0. 05 mm/min. concurrent with experimental test, numerical simulation was performed using particle flow code in two dimension. Firstly calibration of PFC was done using experimental results. Secondly, numerical model with dimension of 14cm*11cm was prepared. Then, five PDC cutter angles were built, i. e. 0° , 15° , 30° , 45° and 60° . These cutters were situated at lower part of the model and move in positive side of y direction by rate of 0. 01 mm/min. the results show that failure patterns were affected by PDC angle. Also maximum failure load was controlled by failure pattern. The maximum failure load was decreased by increasing the PDC cutter angle. The maximum failure load was related to angle of 0. The minimum failure load was related to angle of 60. The experimental results were similar to numerical simulations out puts.

In this work, the effect of rock bolt angle on the shear behavior of Rock Bridges is investigated using the particle flow code in two dimensions (PFC2D) for three different Rock Bridge lengths. Firstly, the calibration of PF2D is performed to reproduce the gypsum sample. Then the numerical models with the dimensions of 100 mm * 100 mm are prepared. The Rock Bridge is created in the middle of the model by removal of the narrow bands of discs from it. The uniaxial compressive strength of the Rock Bridge is 7. 4 MPa. The Rock Bridge lengths are 30 mm, 50 mm, and 70 mm. The rock bolt is calibrated by a parallel bond. The tensile strength of the simulated rock bolt is 360 MPa. One rock bolt is implemented in the Rock Bridge. The rock bolt angles related to the horizontal axis are the changes from 0 to 75 degrees. Totally, 18 models are prepared. The shear test condition is added to the models. The normal stress is fixed at 2 MPa, and the shear load is added to the model till failure occurs. The results obtained show that in a fixed rock bolt angle, the tensile crack initiates from the joint tip and propagates parallel to the shear loading axis till coalescence to rock bolt. In a constant Rock Bridge length, the shear strength decreases with increase in the rock bolt angle. The highest shear strength occurs when the rock bolt angle is 0° .

In this work, the interaction between the semi-circular space and the neighboring joint with and without the presence of rock bolts was investigated using the particle flow code (PFC) approach. For this purpose, firstly, the calibration of PFC was performed using both the Brazilian experimental test and the uniaxial compression test. Secondly, a numerical model with the dimension of 100 mm * 100 mm was prepared. A semi-circular space with a radius of 25 mm was situated below the model. A joint with a length of 40 mm was situated above the space. The joint opening was 2 mm. The joint angles related to the horizontal direction were 0° , 15° , 30° , 45° , 60° , and 75° . Totally, 6 different configurations of the semi-circular space and neighboring joint were prepared. These models were tested with and without the presence of vertical rock bolts by the biaxial test. The rock bolt length was 50 mm. The value of the lateral force was fixed at 2 MPa. An axial force was applied to the model till the final failure occurred. The results obtained showed that the presence of rock bolts changed the failure pattern of the numerical model. In the absence of rock bolts, two tensile wing cracks initiated from the joint tip and propagated diagonally till coalescence from the model boundary. Also several shear bands were initiated in the left and right sides of the tunnel. In the presence of rock bolts, several shear bands were initiated in the left and right sides of the tunnel. The compressive strength with the presence of rock bolts was more than that without the presence of rock bolts. The failure stress had a minimum value when the joint angle was 45° .