The rock fragmentation and crack propagation under TBM tunneling based on particle flow code

Abstract The rock fragmentation and crack propagation of anisotropic induced by tunnel boring machine (TBM) tunneling is studied in this paper. First, a numerical model based on the 2D particle flow code (PFC2D) established calibrated to reveal four stages fragmentation. In Stage I (indentation depth 0–0.4 mm), indentation force beneath cutterhead increases decreases dramatically with accumulation release mechanical energy. Such phenomenon indicates that hydrostatic core (crushed zone) can be observed. II 0.4–1.1 many median cracks propagate force. Meanwhile, pushed because energy reaccumulated specimen. III 1.1–2.6 lateral begin develop due further increase depth. IV 2.6–5 continue propagate, chips found sides cutterhead. Then, increasing confining pressure, gradually maximum angle 70.5°. Furthermore, magnitude intrusion velocity seriously influence evolution during Stages are more obvious higher