Rock breaking process by TBM disc cutters in heterogeneous granite based on a new FDEM modeling

Using the combined finite-discrete element method (FDEM), a modeling approach for heterogeneous granite is proposed to study the mechanical properties and failure behaviors of specimens. The rock breaking laws of heterogeneous granite by disc cutters are also investigated, focusing on the effects of specimen size, cutter blade width, confining pressure, and cutter spacing. The following conclusions are drawn: (1) A Weibull distribution-based method can be used to establish an FDEM numerical model for heterogeneous granite; (2) Uniaxial compression, Brazilian splitting, and triaxial compression simulations validate the reliability of the new modeling method; (3) The specimen width is preferably not less than 40 cm and its thickness not less than 20 cm; (4) As the width of the disc cutter blade increases, the thrust of the cutter, the maximum size of rock debris, and the horizontal failure range of the specimen increase nearly linearly, with an optimal blade width of 10∼14 mm; (5) Increasing confining pressure initially promotes and then inhibits rock breaking, with a critical confining pressure approximately one-third of the uniaxial compressive strength; (6) The optimal spacing between double disc cutters is 10∼13 cm, ensuring that the rock debris between the cutters is neither too fragmented nor too large.