The Influence of Pre-existing Fault Dip Angle on Fault Activation Characteristics: Insights from Discrete Element Method (DEM) Numerical Simulation Experiments

Pre-existing fault activation is a key inducing factor of geological disasters in engineering construction and mineral resource development. As a core parameter controlling the mechanical properties of faults, the influence law of fault dip angle on activation characteristics remains to be clarified urgently. To reveal this mechanism, this study adopted the discrete element method (DEM) simulation software ZDEM and designed four groups of comparative experiments with fault dip angles of 15°, 30°, 45°, and 60°. The activation process, strain distribution, and failure mode of faults under different dip angle conditions were systematically analyzed. The results show that: the 45° dip angle fault initiates activation the earliest (with a critical compression of only 4.5 km), and its activation process is the most intense with significant concentration of shear strain; the 15° low-dip angle fault is dominated by vertical compressive strain, forming a wide and gentle fold-fracture assemblage; the 30° dip angle fault has the densest secondary fractures with well-developed shear fracture zones; the 60° high-dip angle fault eventually forms a “Y”-shaped fracture assemblage, and the dip angle of the main fault deflects significantly. This study quantitatively reveals the influence of fault dip angle on activation threshold, strain distribution, and failure mode, and provides a theoretical basis and technical reference for engineering stability evaluation and disaster prevention and control in areas with pre-existing faults.