PARTICLE-DEM BASED LINKED BAR STRAIN SOFTENING MODEL AND ITS APPLICATION

Based on finite contact assumption between particles, a linked bar model to transmit the force and moment between particles is proposed. To represent the plastic, damage and fracture process of linked bar, the Mohr-Coulomb model and maximal tensile stress model considering strain softening e ect is introduced. The numerical results of uniaxial extension test and direct shear test with single linked bar show the accuracy of the model. The relationship between equivalent macro strain energy of particles system and the average coordination number is studied. Numerical results show that, for 2D particles system, when the average coordination number equals 5, the equivalent macro strain energy of particles system coincides well with the strain energy computed by approaches based on continuous media (i.e. FEM). The uniaxial compression process of rock is simulated based on the linked bar strain softening model. The results show that, the strain-stress curve of rock during uniaxial compression could be divided to four stages, which are linear stage, hardening stage, softening stage and sliding stage, and the relationships between four stages and damage fracture status of rock are also studied. From the results, with the increase of fracture strain, the failure mode of rock changes from tensile-shear composite fracture pattern to purely compression shear fracture pattern. With the increase of fracture strain, the peak stress and corresponding critical strain increases gradually, however, the fracture degree at peak point and at final state decreases gradually.