Numerical simulation study on rock breaking by high-energy impact stress waves

Impact rock-breaking technology is widely used in drilling due to its high-energy transient nature and strong formation adaptability. Its core mechanism lies in rock damage caused by stress waves from the impact tool, making the study of this process essential. This research establishes a three-dimensional finite-element model of the impact system, incorporating stress wave propagation, rock constitutive relations and strain rate effects to simulate rock breaking. Results show that increasing stress wave amplitude (150–270 MPa) and duration (0.08–0.4 ms) improves rock fragmentation, with maximum energy transfer efficiency exceeding 60%. Below 210 MPa, elastic deformation dominates and specific energy increases; above 210 MPa, stress wave superposition and strain rate effects promote brittle failure, reducing specific energy. Longer durations lower the specific energy, stabilising near 16 MPa after 0.2 ms – below the 20 MPa from amplitude effects. Square waves break rock more effectively than triangular or sinusoidal ones but have lower energy efficiency (52.2% as opposed to 56.6%) due to elastic rebound from instantaneous loading. Square and triangular waves create larger fracture volumes but require higher energy, resulting in greater specific energy. These findings offer guidance for optimising impactor parameters and improving rock-breaking efficiency in deep, hard formations.