A three-dimensional visualization experimental apparatus for seepage failure of filling medium in the fault zone: Development and application

The scientific comprehension of water and mud inrush evolution mechanism resulting from seepage failure of filling medium in the fault is crucial for disaster prevention and management strategies. This study presents the development of a three-dimensional visualization experimental apparatus. The apparatus comprises a steel support frame, a visualized testing chamber, a hydraulic control system, a water pressure loading system, and a particle monitoring and collection system. Its notable feature lies in its capacity to apply high, uniform compressive loads in all three principal directions to perform tests under true triaxial static loading conditions. Through the apparatus, the deformation behavior of filling mediums under triaxial ground stress and the erosion and failure phenomena under water pressure can be simulated. The applied vertical ground stress is 3 MPa, with a horizontal ground stress of 1 MPa. The water pressure can reach up to 3 MPa, with a loading accuracy of 0.001 MPa. Statistical analysis elucidates the quantitative variation of ground stress with depth. The range of stress ratio values is obtained. The changes in the cumulative mass of particle loss, porosity, permeability, shear strength, and viscosity with time are clarified through seepage failure tests. Results delineate three stages of the seepage failure process: an initial slow change phase, followed by an intermittent significant change stage, culminating in a stable phase. During the significant change stage, the flow pattern transitions from Darcy flow to non-Darcy flow, accompanied by notable alterations in permeability, porosity, internal friction angle, and cohesion. Seepage failure emerges as a multifaceted process characterized by real-time fluctuations in strength, viscosity, and permeability. Comparative analysis across different ground stress conditions reveals its pronounced impact on the severity of water and mud inrush incidents. Lower ground stress leads to weaker interlocking between particles, thereby amplifying the likelihood of large-scale water and mud inrush disasters.