Experimental method for fluid-injection-induced seismicity under true-triaxial stress conditions

An experimental method for fluid-injection-induced seismicity under true-triaxial stress conditions, comprising steps of:

• S1:
• fabricating a cubic rock model with side lengths of a cm×a cm×a cm using rock material, diagonally cutting the cubic rock model along a diagonal plane to form a fault plane, drilling a water-injection borehole from a center of a footwall bottom toward the fault plane, and uniformly arranging pore-pressure monitoring boreholes along the fault plane;
• S2:
• coupling a high-precision high-pressure water pump to the water-injection borehole and injecting water to permeate and saturate the fault plane;
• S3:
• applying, via a true-triaxial apparatus, stresses to the fault model to achieve a true-triaxial stress state where major, intermediate, and minor principal stresses are all unequal;
• and maintaining the true-triaxial stress state for a duration of d min;
• S4:
• switching the true-triaxial apparatus from a stress-controlled loading mode to a displacement-controlled loading mode, inducing spontaneous instability in the fault model, and calculating an interseismic period T;
• and
• S5:
• performing, by setting a cycle count N, with T/N as a period, cyclic water injection by alternating between injecting water at a constant rate of e mL/min and not injecting water, or performing water injection at a constant rate of f mL/min at intervals corresponding to an interseismic period T, thereby investigating a mechanism of injection-induced seismicity.