Investigating the Effect of Cutter Edge Shape on Rock Fragmentation Using PFC2D

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Sarfarazi v; Beiralvand n.

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Journal: JOURNAL OF ROCK MECHANICS Year:2017 | Volume:1 | Issue:2 Page(s): 75-88

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Title

Investigating the Effect of Cutter Edge Shape on Rock Fragmentation Using PFC2D

Author(s)

Sarfarazi v | | Beiralvand n. | Issue Writer Certificate

Keywords

TBM

PFC2D

Cutter Edge Shape

Tensile Strength

Confining Pressure

TBM

PFC2D

Abstract

Summary In this paper, the effect of Cutter Edge Shape on the failure mechanism of rock has been investigated using particle flow code in two directions (PFC2D). Particle flow code represents a rock mass as an assemblage of bonded rigid particles. The standard process of generating a PFC2D assembly to represent a test model involves: particle generation, packing the particles, isotropic stress installation (stress initialization), floating particle (floater) elimination and bond installation. In PFC2D circular disks are connected with cohesive and frictional bonds and confined with planar walls. The values assigned to the strength bonds influence the macro strength of the sample. Friction is activated by specifying the coefficient of friction and is mobilized as long as particles stay in contact. Tensile cracks occur when the applied normal stress exceeds the specified normal bond strength. Shear cracks are generated as the applied shear stress surplus the specified shear bond strength either by rotation or by shearing of particles. The Tensile Strength at the contact immediately drops to zero after the bond breaks, while the shear strength decreases to the residual friction value. For all these microscopic behaviours, PFC only requires selection of the basic micro-parameters to define contact and bond stiffness, bond strength and contact friction, but these micro-parameters should provide the macroscale behaviour of the material being modelled. The code uses an explicit finite difference scheme to solve the equation of force and motion, and hence one can readily track initiation and propagation of bond breakage through the system. For this purpose, two numerical models with different Tensile Strength of 5 MPa and 25 MPa were built and compressed by two different Confining Pressures of 5 MPa and 25 MPa, respectively. Eight disc cutters with different edge shape peneterate into the model at the rate of 0. 02 m/s till 4 mm of disc peneteration is reached. Totally 16 simulation has been done. The rock materials, below the cutters, show three different mechanical behavior i. e. failure, plastic and elastic behavior. The failure zone is fully fractured. The plastic zone is consisted of partially micro crack with several major fractures. The elastic zone is an undamaged zone. The shape of cutter edge has important effect on extension of three introduce zones. When Tensile Strength is 5 MPa, the failure stress resulted from penetration of convex-shape cutter is the lowest one, 5. 3 MPa while the number of total cracks is maximum one, 102. It means that the cutter shape controls the failure stress and failure extension when it cuts the weak rock. When Tensile Strength is 25 MPa, the failure stress resulted from penetration of different cutters is similar, 21 MPa, but the extension of failure is largest under Ushape cutter. It means that the cutter shapes has not any effects on the failure stress when it cuts the hard rock while the U-shape cutter produce the largest failure zone. The results show that convex-shape edge and U-shape edge cutters have the best performance when Tensile Strength of rock is 5MPa and 25 MPa, respectively. The results also showed that the failure stress increases with increasing Tensile Strength, while the failure extension decreases.

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APA: Copy

Sarfarazi, v,, & Beiralvand, n.. (2017). Investigating the Effect of Cutter Edge Shape on Rock Fragmentation Using PFC2D. JOURNAL OF ROCK MECHANICS, 1(2 ), 75-88. SID. https://sid.ir/paper/268318/en

Vancouver: Copy

Sarfarazi v,, Beiralvand n.. Investigating the Effect of Cutter Edge Shape on Rock Fragmentation Using PFC2D. JOURNAL OF ROCK MECHANICS[Internet]. 2017;1(2 ):75-88. Available from: https://sid.ir/paper/268318/en

IEEE: Copy

v, Sarfarazi, and n. Beiralvand, “Investigating the Effect of Cutter Edge Shape on Rock Fragmentation Using PFC2D,” JOURNAL OF ROCK MECHANICS, vol. 1, no. 2 , pp. 75–88, 2017, [Online]. Available: https://sid.ir/paper/268318/en

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