Permeability evolution of prefabricated grouted curtain specimens with artificial defects under cyclic loading/unloading

Two types of rock specimens simulating grout curtains were prepared: one featuring solely an axial through-hole and the other featuring combined axial and transverse holes (termed combined-hole specimens). Coupled permeability-damage tests under cyclic loading-unloading were conducted to analyze the effects of peak stress level, confining pressure, seepage pressure difference, and defect geometry (curtain filling configuration) on permeability evolution and damage accumulation. The results indicate that: (1) Peak stress level is the primary factor governing damage development rate; (2) Higher confining pressure mitigates damage in the surrounding rock and decelerates permeability increase; (3) Larger seepage pressure difference (≥ 0.5 MPa) significantly enhances the stability and accuracy of permeability measurements; (4) For combined-hole configurations, increasing the transverse hole area (and thus the grout volume) provides more lateral seepage paths, effectively reducing axial permeability by up to two orders of magnitude. This study provides an experimental framework for assessing the long-term sealing performance of grouted curtains under repeated dynamic loading akin to blasting disturbances.