Distribution patterns of rock mass displacement in deeply buried areas induced by active fault creep slip at engineering scale

Active fault creep slip induces deformation of rock mass buried deeply in fault zones that significantly affect the operational safety of long linear projects passing through it. Displacement distribution patterns of rock masses in active fault zones which have been investigated previously are the key design basis for such projects. Therefore, a discrete element numerical model with different fault types, slip time, dip angles, and complex geological features was established, and then the creep slip for normal, reverse, and strike-slip faults were simulated to analyze the displacement distribution in the fault rock mass. A disk rotation test system and the corresponding laboratory test method were developed for simulating rock mass displacement induced by creep slippage of faults. A series of rotation tests for soft-and hard-layered specimens under combined compression and torsional stress were conducted to verify the numerical results and analyze the factors influencing the displacement distribution. An S-shaped displacement distribution independent of fault dip angle was identified corresponding to reverse, normal, and strike-slip faults. The results indicated that the higher the degree of horizontal extrusion, the softer the rock mass at the fault core, and the higher the degree of displacement concentration in the fault core; about 70% of the creep slip displacement occurs within this zone under 100 years of creep slippage.