Development of experimental system for rock anisotropic seepage under true triaxial stress

In order to study the mechanical properties and anisotropic seepage behavior of rocks under complex stress conditions in deep strata, an anisotropic seepage dynamic monitoring system for true triaxial stress conditions was developed. In the process of research and development, four key technologies have been successfully broken through: (1) the use of an independently designed sealing system ensures complete sealing during seepage experiments, reduces experimental errors, and eliminates the edge effect through the six-axis linkage technology; (2) the specially designed multifunctional platen is capable of hydraulic fracturing, seepage, and data acquisition in the true triaxial experiments; (3) Integrated acoustic emission and seepage monitoring system, which can realize real-time dynamic monitoring of crack extension and seepage evolution under real triaxial stress conditions; (4) The control system supports real triaxial stress loading of up to 280 MPa, and it has a stress response sensitivity of 0.5 kPa/s, which ensures high-precision loading and monitoring. The crack extension modes of rocks under true triaxial stress conditions were systematically studied to reveal the dynamic relationship between crack extension and seepage paths. The results show that cracks preferentially extend in the direction of maximum principal stress, leading to a significant increase in seepage rate, while seepage rate lags in the direction of minimum principal stress due to the crack closure effect. A nonlinear "rise-decline-rise" dynamic relationship was observed between crack extension and seepage rate. This study provides new insights into the coupling mechanism between crack extension and seepage behavior under complex stress conditions.