A VUMAT of modified Mohr-Coulomb model and its application in TBM tunnelling simulation

The modified Mohr-Coulomb model which combines conventional Mohr-Coulomb criterion with the maximal tensile stress criterion, can well describe the mechanical properties of rock. Based on the Fortran language, the modified Mohr-Coulomb model combined with a plastic damage law and composite failure criteria, is implemented in a finite element analysis package through the user subroutine VUMAT (vectorized user defined material subroutine). Numerical simulations of uniaxial tensile numerical test were performed to verify the precision and reliability of VUMAT. Then the dynamic process when TBM tunnelling through the composite rock was simulated with the user subroutine. Results show that the developed VUMAT can well describe the mechanical behavior of the rock in the tunnelling process.